© 2018 Camilo Lopera Higuita -...
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EFFECTS OF LEVEL OF DIETARY CATION-ANION DIFFERENCE AND DURATION OF PREPARTUM FEEDING ON PERFORMANCE AND METABOLISM OF DAIRY COWS By CAMILO LOPERA HIGUITA A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2018
Transcript of © 2018 Camilo Lopera Higuita -...
EFFECTS OF LEVEL OF DIETARY CATION-ANION DIFFERENCE AND DURATION OF PREPARTUM FEEDING ON PERFORMANCE AND METABOLISM OF DAIRY
COWS
By
CAMILO LOPERA HIGUITA
A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
UNIVERSITY OF FLORIDA
2018
© 2018 Camilo Lopera Higuita
To my fiancée Catalina for her endless support. To my parents Juan and Elizabeth for making me the man who I am and teaching me the importance of perseverance to
accomplish my objectives. To my sister Manuela for always being there. To my cousin Mateo for the strength, no matter where you are, you will be always with me.
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ACKNOWLEDGMENTS
I would like to first express my appreciation to my major professor and advisor,
Dr. José Eduardo P. Santos, for offering me the opportunity to come to the University of
Florida to accomplish a dream, for giving me the honor of being part of his team, and for
so many invaluable lessons he has taught me.
I would also like to thank my other committee members, Dr. Corwin Nelson, Dr.
Charles Staples, and Dr. Jimena Laporta, for their continued interest in my education,
their help and especially their patience. Special thanks to Dr. William W. Thatcher for
his time working with me through the data and for his advice and guidance that helped
me make decisions about how to handle challenging situations. I would also like to
thank Dr. Peter Hansen for his time, advice, and support during a very difficult time in
my personal life. His advice and help were invaluable and helped me recover and return
more prepared to compete my degree.
Special thanks to Dr. Natalia Martinez-Patiño, for her help, support, advice and
for the patience to teach me. If it was not for her help and advice, I would not be here. It
was a complete pleasure and an immense honor to work with such a smart incredible
person.
I would also like to extend my thanks to Dr. Ricardo Chebel, and Dr. Klibs N.
Galvão for allowing me to use their laboratories and facilities.
Infinite thanks to my labmates Achilles Vieira-Neto, Roney Zimpel, and Leticia
Sinedino for their assistance throughout the last two years, especially during the data
collection period. Your help was invaluable; I especially thank them for their friendship,
advice and support, without them I could not have done it.
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To all visiting professors, graduate students, and interns who have assisted me
at some point throughout the last two years, Dr. Maria Lucia Gambarini, Dr. Fernanda
Ferreira, Dr. Ricarda Santos, Dr. Bolivar Faria, Michael Poindexter, Marcos Zenobi,
Sossi Iacovides, Carolina Collazos, Paula Mollinari, Diandra Lezier, Bárbara Piffero,
Murilo Rômulo, and William Ortiz for their hard work and commitment. Their assistance
made possible the completion of my project.
I extend my sincere appreciations to the staff of the University of Florida Dairy
Research Unit, Todd Pritchard, Eryck Lockyer, Patty Best, Travis Fulchur, and the night
shift crew, for letting me use the cows and for their assistance during the process.
My thanks go to the staff in the Department of Animal Sciences, particularly to
Renee Parks-James, Joyce Hayen, and Pam Krueger for their assistance during my
graduate studies at the University of Florida.
Finally, I would like to thank my family, friends and especially my fiancée Catalina
for their endless support, patience and encouragement that made this whole process a
little easier.
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TABLE OF CONTENTS Page
ACKNOWLEDGMENTS .................................................................................................. 4
LIST OF TABLES ............................................................................................................ 8
LIST OF FIGURES .......................................................................................................... 9
LIST OF ABBREVIATIONS ........................................................................................... 10
ABSTRACT ................................................................................................................... 12
CHAPTER
1 INTRODUCTION .................................................................................................... 13
2 LITERATURE REVIEW .......................................................................................... 16
Dry Period ............................................................................................................... 17 Transition Period ..................................................................................................... 19 Transition Period, Energy, and Mineral Metabolism ............................................... 24
Nutrient Requirements ..................................................................................... 24 Energy Metabolism ........................................................................................... 26
Mineral Requirements ...................................................................................... 32
Calcium ................................................................................................................... 43
Calcium Metabolism................................................................................................ 46 Calcium Absorption .......................................................................................... 46 Calcium Homeostasis ....................................................................................... 49
Hypocalcemia ......................................................................................................... 52 Acidogenic Diets ..................................................................................................... 56
Acid-Base Balance ................................................................................................. 59
3 EFFECTS OF LEVEL OF DIETARY CATION-ANION DIFFERENCE AND DURATION OF PREPARTUM FEEDING ON PERFORMANCE AND METABOLISM OF DAIRY COWS. ......................................................................... 62
Summary ................................................................................................................ 62
Introductory Remarks.............................................................................................. 63 Materials and Methods............................................................................................ 66
Cows and Housing ........................................................................................... 66 Feeding Management and Treatments ............................................................ 67 Ingredient Sampling, Chemical Analyses, and Calculation of DM Intake ......... 68 Body Weight and Body Condition Score........................................................... 69 Blood Sampling and Processing ....................................................................... 69 Sampling Whole Blood and Measurements of Ionized Ca, Na, K, and
Measures of Acid-Base Status ...................................................................... 70
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Blood Assays .................................................................................................... 70
Urine Collection and Analysis ........................................................................... 71 Measurement and Analysis of Colostrum ......................................................... 72
Measurements of Yields of Milk and Milk Components .................................... 73 Measurement of Net Energy Balance Prepartum ............................................. 73 Characterization and Diagnosis of Health Problems ........................................ 74 Reproductive Management and Reproductive Responses............................... 75 Statistical Analysis ............................................................................................ 76
Results .................................................................................................................... 79 Intake, Measures of Energy Status, and Acid-Base Balance in the Early Dry
Period ............................................................................................................ 79 Intake and Measures of Energy Status in the Late Dry Period ......................... 80 Acid-Base Balance and Urinary Excretion of Minerals Prepartum .................... 81
Concentrations of Minerals and Metabolites in Blood ....................................... 81 Colostrum Yield and Composition .................................................................... 82
Lactation Performance ..................................................................................... 83
Acid-Base Balance Postpartum ........................................................................ 83 Blood Concentrations of Minerals and Metabolites Postpartum ....................... 84 Health and Survival .......................................................................................... 85
Reproduction .................................................................................................... 86 Discussion .............................................................................................................. 86
Final Remarks ......................................................................................................... 94
4 CONCLUSIONS ................................................................................................... 123
LIST OF REFERENCES ............................................................................................. 127
BIOGRAPHICAL SKETCH .......................................................................................... 149
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LIST OF TABLES
Table page 3-1 Characteristics of cows enrolled in the experiment according to treatment
(mean ± SD) ....................................................................................................... 96
3-2 Ingredient composition and nutrient content of diets fed during the prepartum and postpartum periods ...................................................................................... 97
3-3 Effects of level of dietary cation-anion difference on measures of energy status from d -42 to -22 relative to calving, blood acid-base status and concentrations of minerals in Holstein cows ..................................................... 100
3-4 Effects of duration of prepartum feeding and level of dietary cation-anion difference on measures of energy status in the last 21 d of gestation in Holstein cows ................................................................................................... 102
3-5 Effects of duration of prepartum feeding and level of dietary cation-anion difference on measures of blood acid-base balance, and urinary pH and excretion of minerals in Holstein cows prepartum ............................................ 103
3-6 Effects of duration of prepartum feeding and level of dietary cation-anion difference on blood concentrations of minerals and metabolites in Holstein cows prepartum ................................................................................................ 105
3-7 Effects of duration of prepartum feeding and level of dietary cation-anion difference on colostrum yield and composition in Holstein cows ...................... 106
3-8 Effects of duration of prepartum feeding and level of dietary cation-anion difference on productive performance in the first 42 d postpartum in Holstein cows ................................................................................................................. 109
3-9 Effects of duration of prepartum feeding and level of dietary cation-anion difference on measures of acid-base balance in Holstein cows postpartum .... 111
3-10 Effects of duration of prepartum feeding and level of dietary cation-anion difference on blood concentrations of minerals and metabolites in Holstein cows postpartum .............................................................................................. 112
3-11 Effects of duration of prepartum feeding and level of dietary cation-anion difference on health in Holstein cows ............................................................... 113
3-12 Effects of level of dietary cation-anion difference and duration of prepartum feeding on reproduction in Holstein cows ......................................................... 115
3-13 Cox’s hazard regression model for time to pregnancy according to duration of prepartum feeding and level of dietary cation-anion difference ........................ 116
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LIST OF FIGURES Figure page 3-1 Prepartum DM intake and urine pH .................................................................. 117
3-2 Concentrations of whole blood ionized Ca, plasma total Ca, plasma total Mg, and plasma total P in dairy cows fed prepartum acidogenic diets .................... 118
3-3 Concentrations of glucose, NEFA, and BHBin plasma of dairy cows fed prepartum acidogenic diets .............................................................................. 119
3-4 Yields of milk and energy-corrected milk, body weight and body condition score of dairy cows fed prepartum acidogenic diets ......................................... 120
3-5 Daily risk of subclinical hypocalcemia based on concentration of iCa ≤ 1.0 mM in whole blood, tCa ≤ 2.0 mM in plasma, or tCa < 2.15 mM in plasma in cows fed prepartum acidogenic diets ............................................................... 121
3-6 Survival curves for days from calving to pregnancy according to duration of prepartum feeding and level of DCAD .............................................................. 122
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LIST OF ABBREVIATIONS
AMP Adenosine monophosphate
AI Artificial insemination
ATP Adenosine triphosphate
BCS Body condition score
BHB Beta hydroxybutyrate
BW Body weight
Ca Calcium
CV Coefficient of variation
d Day
DCAD Dietary cation-anion difference
DIM Days in milk
DM Dry matter
ECM Energy corrected milk
FCM Fat corrected milk
HR Hazard ratio
iCa Ionized Calcium
Ig Immunoglobulin
LSM Least squares mean
mM Millimolar
Mmol/L Millimol per liter
NE Net energy
NEFA Non-esterified fatty acids
NRC National Research Council
P-value Probability value
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pCO2 Partial pressure of carbon dioxide
pO2 Partial pressure of oxygen
PTH Parathyroid hormone
SCC Somatic cell count
SEM Standard error of the mean
sO2 Saturation of oxygen
tCa Total calcium
tCO2 Total dissolved carbon dioxide
tMg Total magnesium
tP Total phosphorus
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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science
EFFECTS OF LEVEL OF DIETARY CATION-ANION DIFFERENCE AND DURATION
OF PREPARTUM FEEDING ON PERFORMANCE AND METABOLISM OF DAIRY COWS
By
Camilo Lopera Higuita
May 2018
Chair: José Eduardo P. Santos Major: Animal Sciences
Objectives of the experiment presented in Chapter 3 were to evaluate the effects
of feeding diets with two dietary cation-anion differences during the last 42 or 21 d of
gestation on performance and metabolism of dairy cows. Reducing the dietary cation-
anion difference from positive to negative values in the last 3 weeks of gestation is
expected to benefit mineral metabolism at the onset of lactation, which usually favors
lactation performance. Lowering the negative dietary cation-anion difference from -70 to
-180 mEq/kg of dry matter (DM) reduced prepartum dry matter intake, and increased
concentrations of ionized calcium (iCa) in blood around calving. Extending the duration
of feeding the diets with negative dietary cation-anion difference from 21 to 42 days
reduced gestation length, milk yield, and impaired the reproductive performance of the
cow in the subsequent lactation. Reducing the dietary cation-anion difference from -70
to -180 mEq/kg for the last 21 d of gestation had no impacts prepartum or during the
subsequent lactation, but extending the duration of prepartum feeding to 42 d had
detrimental consequences to the subsequent lactation productive and reproductive
performance.
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CHAPTER 1 INTRODUCTION
Nearly all cows experience a decrease in blood concentration of calcium (Ca) at
the onset of lactation (Goff, 2014); in fact, 5% of the cows in the United States develop
clinical hypocalcemia, also known as milk fever every year (USDA, 2007). Furthermore,
more than 40% of cows in their second or greater lactation, and 25% of cows in the first
lactation are diagnosed with subclinical hypocalcemia (Reinhardt et al., 2011; Ribeiro et
al., 2013). Hypocalcemia is defined as disease of adult dairy cows in which acute calcium
deficiency causes progressive neuromuscular dysfunction (Oetzel, 1988). The main
reason for hypocalcemia is the sudden and large increase in Ca needs for synthesis of
colostrum and milk with the onset of lactation. Colostrum contains approximately 2.3 g of
Ca/kg of colostrum produced and a cow producing 10 kg of colostrum requires an amount
of Ca equivalent to 7 to 8 times the entire plasma pool (Goff and Horst, 1997; Horst et al.,
2005). For many cows, the influx of Ca into the mammary gland for synthesis of colostrum
and milk is faster than they can accommodate by increasing bone resorption or
gastrointestinal absorption, which leads to reductions in concentrations of total Ca (tCa)
and ionized Ca (iCa) in plasma, but also in the intracellular fluids (Goff et al., 2014;
Martinez et al., 2014).
Ender et al. (1971) reported a series of experiments conducted in the 1950’s and
1960’ in Scandinavia in which diets of different alkalinity, were fed with the aim to
manipulate blood pH prepartum and influence Ca metabolism. Briefly, cows fed diets with
less alkalinity, or acidogenic, had increased concentration of Ca in blood and reduced
incidence of clinical hypocalcemia. Their findings led to the development of the concept
of manipulating the mineral composition of diets, particularly the so called strong ions, to
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reduce hypocalcemia, and introducing the concept of dietary cation-anion difference
(DCAD).
In dairy herds, it is a common practice to group dry cows of similar gestation
days to facilitate management. In some instances, producers might elect to have fewer
groups to minimize regrouping of animals and the consequent negative social
interactions in the prepartum period (Weich et al., 2013). Minimizing regrouping is
considered by many a component of sound transition management programs, although
it is not a required management for success. It is known that prepartum cows at
different stages of the dry period have different ability to consume dry matter (DM) and
dietary management is aimed to meet the nutrient requirements of the dam and of the
developing fetus, in addition to accommodate the needs to adapt the cow and the
digestive system to the more digestible lactation diet fed postpartum (Goff and Horst,
1997). It is thought that, in some circumstances, minimizing cow movement and
regrouping will result in improved performance and intake (Phillips and Rind, 2001; von
Keyserlingk et al., 2008), although data on this subject in prepartum cows is
questionable. Evidences of no negative consequences are observed with regrouping
(Silva et al., 2013).
In addition to the sequestration and drain of Ca, there is a large increase in the
needs for other nutrients and calories with parturition and the onset of lactation, and it
has been shown that that diets with a negative DCAD can decrease DM intake (Hu and
Murphy, 2004; Charbonneau et al., 2006). Therefore, there is speculation that feeding
diets with negative DCAD might have detrimental impacts on cow metabolism, by
increasing adipose tissue triacylglycerol mobilization resulting in increased
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concentrations of nonesterified fatty acids (NEFA) at calving resulting in greater risk for
ketosis and fatty liver (Vandehaar et al., 1999; Moore et al., 2000). If cows are fed
acidogenic diets that result in uncompensated metabolic acidosis, it is possible that the
changes in acid-base status compromise metabolism (Bigner et al., 1996), which might
predispose them to subsequent problems in early lactation. Because formulation for
DCAD requires accurate analysis of minerals in feedstuffs, it is common that
discrepancies exist between the formulated values and the DCAD offered to cows.
Large variability exists in composition of feedstuffs, and mineral content is highly
variable within the same dietary ingredient, particularly forages (St-Pierre and Weiss,
2017). Changes in concentrations of strong ions, Na+, K+, Cl-, and S2-, will easily alter
the DCAD of the diet offered to prepartum cows (Stone and Mosley, 2017).
Most experiments have focused on the risks of feeding acidogenic diets on
hypocalcemia, with some reporting subsequent productive and health performance.
Very few experiments have evaluated the impact of altering the duration of feeding
acidogenic diets prepartum on subsequent production, health, and reproduction in dairy
cows. The limited data on extending the duration of feeding beyond the traditional 21 d
prepartum had been evaluated by Weich et al. (2013) and Wu et al. (2014), but both
experiments fed diets with the same level of DCAD values within each experiment.
Therefore, the experiment presented in this thesis was designed to understand
the role of prepartum diets differing in DCAD on metabolism and performance of the
dairy cow when fed for two durations. My goal was to gain a better understanding of
proper diet formulation for the prepartum dry period, and explore strategies to improve
peripartum health and performance of dairy cows.
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CHAPTER 2 LITERATURE REVIEW
It is well known that nearly all dairy cows will experience a decrease in blood
calcium (Ca) concentration or even develop hypocalcemia at the onset of lactation
(Goff, 2014). According to the USDA (2007) 5% of the cows in the United States will
develop clinical hypocalcemia every year, and 25% of cows in the first lactation and
40% of cows in their second or greater lactation will develop subclinical hypocalcemia
(Reinhardt et al., 2011). However, Ender et al. (1971) demonstrated that feeding
prepartum diets richer in strong anions relative to strong cations increased blood
concentrations of Ca and prevented clinical hypocalcemia, also called milk fever, in
dairy cows. These findings eventually led to the practice of feeding acidogenic diets to
decrease hypocalcemia on dairy farms, and introduced the concept of dietary cation-
anion difference (DCAD) for formulation of diets for prepartum dairy cows.
Although diets with negative DCAD have become a common practice on most
dairy farms in the United States and worldwide, concerns and unknowns remain relative
to their effects on dairy cows. The premise is that acidogenic diets induce a
compensated metabolic acidosis and, as consequence, can reduce dry matter (DM)
intake during the last weeks prepartum (Charbonneau et al., 2006), a period already
characterized by reduced appetite and potential risks for subsequent metabolic
problems when the new lactation starts. It has been speculated that exacerbated
metabolic acidosis in late gestation might further enhance the state of insulin resistance
in dairy cows (Bigner et al., 1996), although it has only been reported when cows were
fed excessive amounts of acidogenic salts resulting in a diet with very low DCAD
(Bigner et al., 1996), but not when cows were fed acidogenic diets with DCAD values
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within the typical range recommended for prepartum cows which are from -50 to -150
mEq/kg of DM (NRC, 2001; Grünberg et al., 2011). Nevertheless, it remains unknown
what duration of feeding acidogenic diets is needed to prevent hypocalcemia or
optimize postpartum health in dairy cows. Is the traditional 21 days (d) of feeding the
optimum length of duration of feeding acidogenic diets or would extending the feeding
for the entire dry period of 42-d be detrimental to postpartum health and performance of
dairy cows? The goal of the experiment in this thesis was is to evaluate the impacts of
feeding prepartum diets of two negative DCAD values prepartum for two distinct
durations on intake, lipid and energy metabolism, and mineral homeostasis. The
hypothesis was that extending the duration of feeding the more negative acidogenic diet
prepartum at two levels of negative DCAD would not be detrimental to metabolism,
health, and subsequent lactation performance.
Dry Period
The mammary glands of dairy cows require a non-lactating period before
parturition to achieve maximum milk production during the ensuing lactation (Gulay et
al., 2003). It allows the mammary epithelial component to regress, proliferate, and
differentiate (Capuco et al., 1997). Therefore, an adequate dry period length that
incorporates proper management and nutrition of the dry cow are critical for achieving
adequate postpartum health and productivity in the following lactation.
The need for a dry period to sustain the subsequent milk production in dairy cows
has been established, but the determination of the optimal length has been widely
discussed. Coppock et al. (1974) observed that the optimal length suggested was from
40 to 60 d, and then was confirmed by Sørensen and Enevoldsen (1991) because of
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the little or no loss in subsequent milk production. Several experiments have
demonstrated that reducing the dry period from the suggested interval of 40 to 60 d will
result in a decrease in milk production of 2 to 6 kg/d in the subsequent lactation
(Coppock et al., 1974; Gulay et al., 2003; Rastani et al., 2005), although this reduction
was dependent on the parity of the cow (Santschi et al., 2011). Production in the
subsequent lactation was not affected by reducing the dry period from 60 to 35 d in
cows starting the 3rd or greater lactation, but the short dry period reduced milk yield of
cows starting the 2nd lactation (Santschi et al., 2011).
Swanson (1965) took 5 pair of twins and divided them into two treatments, one
twin having a 60-d dry period and the other twin milked continuously. Animals were
followed during 4 consecutive calvings. Twins in the dry period were fed with only
roughage whereas the continuously milked twins had an addition of concentrates. Diets
were selected to favor the continuously milked twins. Twins with the 60-d dry period
produced 908 kg and 1,400 kg more of milk than twins that were milked continuously
independent of the diet. Capuco et al. (1997) reported that this increased milk yield
when the dry period length was 60 d, was due to an 80% increase replacement of
damaged epithelial cells in the mammary gland compared to cows with no dry period.
The current NRC (2001) recommendation is that cows should not gain body
weight (BW) during the dry period, except for the BW associated with growth of the
fetus and fetal membranes. The purpose of controlling the nutritional status of the dry
cow is to minimize the risk of cows becoming overconditioned, which minimizes the risk
of obesity and early lactation metabolic diseases (Gearhart et al., 1990).
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The dry period, particularly the last 3 weeks of gestation, is characterized by
dramatic changes in endocrine and metabolic status. Increased concentrations of leptin,
insulin, and glucose, and reduced concentrations of nonesterified fatty acids (NEFA)
and beta hydroxybutyrate (BHB) are characteristic responses during most of the period
(Holtenius et al., 2003). Concurrent, concentrations of prolactin decrease (Accorsi et al.,
2005). As calving approaches, concentrations of estrogens, cortisol, and growth
hormone increase, whereas those of progesterone and insulin-like growth factor 1
decrease (Tucker, 2000). These changes likely prepare the cow for parturition and
lactogenesis (NRC, 2001). In summary, the dry period is not only a period of rest with
no lactation, but also a stage in the lifecycle of the cow needed to reestablish mammary
cell population and functionality, to synthesize colostrum, and to prepare the mammary
gland to achieve optimal production during the subsequent lactation.
Transition Period
The transition period is defined as the phase that interchanges the late gestation
dry period with early lactation and recovery of the reproductive tract after calving. It
comprises the last 3 weeks of gestation and first 3 weeks after calving (Grummer, 1995;
Drackley, 1999; Block, 2010). It is critically important to health of the dairy cow as 30 to
50% of all postpartum cows are affected by some form of metabolic or infectious
disease in the first 4 to 8 weeks postpartum (LeBlanc, 2010; Ribeiro et al., 2013; 2016;
Santos et al., 2010). The increased risk of health disorders in early lactation has been
associated with reduced measures of immune function (Kehrli et al., 1989), particularly
innate immunity, which is critical for uterine and mammary defenses against infections.
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Changes in tissue metabolism, nutrient utilization (Grummer, 1995), and
suppression of the immune system (Ingvartsen and Moyes, 2013) occur during the
transition period. Feed intake often decreases by 30% in the last days of gestation
(Bertics et al., 1992; Hayirli et al., 2002), yet nutrient demands are greatest to support
conceptus growth, with more than 70% of growth occurring in the last 60 d of pregnancy
(Eley et al., 1978; House and Bell, 1993), at a maximal rate (of 220 g/d; Eley et al.,
1978). Accretion of tissue by conceptus increases as parturition approaches, increasing
from 398 kcal/d of net energy and 36 g/d of protein gain at 190 d of gestation to 821
kcal/d of net energy and 117 g/d of protein, at 240 to 270 d of gestation (Bell et al.,
1995). At the same time, initiation of milk synthesis resulting in colostrum production
requires another 1.1 Mcal of net energy and 140 to 150 g of protein per kg of colostrum
(Goff and Horst, 1997), with the typical cow producing 8 to 12 kg of colostrum and
second milk in the first day after calving. The combined growth of the fetus with
colostrum synthesis place an important nutritional burden on the cow immediately
before parturition (Laster and Prior, 1979; van Saun and Sniffen, 2014).
Endocrine adaptations to parturition and a new lactation are usually associated
with increased rates of lipolysis. As cows approach calving, tissues become less
responsive to insulin, because of the negative energy balance (Oikawa and Oetzel,
2006), and the increased plasma concentrations of growth hormone (Kunz et al., 1985),
that is known to counter-act the effects of insulin on lipogenesis. As the mechanisms of
calving are triggered with the release of fetal cortisol, placental production of
progesterone and estrogens markedly decline (Chew et al., 1979), and the changes in
these steroids are thought to influence adipose tissue metabolism. Coupled with the
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endocrine changes, the reduction in DM intake and, therefore, nutrient intake as
parturition approaches favors increased mobilization of triacylglycerol from adipose
tissue (Grummer, 1995; Janovick et al., 2011; Mann et al., 2015) and glycogen from the
liver (Formigoni and Trevisi, 2003). Lipid mobilization is a physiological adaptation
acquired by mammals to survive during times of reduced nutrient and energy availability
(Drackley, 1999). It is defined as a shift in the rates of lipogenesis and lipolysis favoring
the latter within the adipose tissue (Contreras and Sordillo, 2011). As a result, there is
an increase in circulating concentration of NEFA in blood plasma, which increases
gradually during the prepartum period, but rapidly in the last 3 d of gestation and the
first day or two postpartum reaching concentrations above 1.0 mM in many cows
(Janovick et al., 2011). Bertics et al. (1992) showed that a portion of the increase in
NEFA concentrations around calving was not a response of reduced DM intake, but
likely a result of hormonal influence. The authors “force-fed” rumen-cannulated cows to
overcome the depression in intake prepartum and showed that, despite equal “DM
intake”, plasma concentrations of NEFA and hepatic concentrations of triacylglycerol
increased the day after calving (Bertics et al., 1992). High NEFA concentration
prepartum (NEFA ≥ 0.5 mM) and postpartum (NEFA ≥ 0.7 mM) have been associated
with milk loss in the subsequent lactation (Ospina et al., 2010; Chapinal et al., 2011;
Ribeiro et al., 2013), increased odds of culling (Seifi et al., 2011; Roberts et al., 2012),
increased risk of diseases such as displaced abomasum (LeBlanc et al., 2005), metritis
and clinical ketosis (Ospina et al., 2010), and decreased pregnancy at first service
(Ospina et al., 2010). Therefore, excessive lipolysis in late gestation and early lactation
is detrimental to health, production, and reproduction of dairy cows.
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In well-fed prepartum cows, plasma concentrations of glucose prepartum remain
relatively stable and high, but they sharply increase on the day before and day of
calving following by a dramatic decrease in the following 2 to 3 d postpartum (Vazquez-
Anon et al., 1994; Grummer, 1995; Janovick et al., 2011). The increase in glucose
concentrations is a response to the signals to trigger calving such as cortisol (Massip,
1980; Rizza et al., 1982), but also the typical stress response with mobilization of tissue
glycogen and increased gluconeogenesis (Hargreaves et al., 1996). The increase at
calving result from increased glucagon and glucocorticoid concentrations that promote
the depletion of hepatic glycogen stores (Grummer, 1995; Mann et al., 2015). Although,
the demand for glucose by mammary tissue for lactose synthesis substantially
increases after calving, hepatic glycogen stores begin to replete and are restored by
day 7 postpartum (Vazquez-Anon et al., 1994). In the meantime, the liver transcriptome
changes to adapt to the negative energy balance during the final days of gestation and
the onset of lactation (Ha et al., 2017). Pyruvate carboxylase mRNA was upregulated
from the day of calving to 28 days in milk, increasing machinery capable of
gluconeogenesis (Greenfield et al., 2000). This increased gluconeogenic capacity is a
hallmark in support of lactation (Grummer, 1995).
Another important change during the transition period occurs in the rumen. There
are changes in the bacterial population with shifts away from lactate producers, which
are bacteria possessing alpha-amylase that digest starch such as Streptococcus bovis
and lactobacilli because, of the decrease in readily fermentable starches in the diet of
most dry cows (Tajima et al., 2001). Therefore, the population of those bacteria
(primarily Megasphaera elsdenii and Selenomonas ruminantium) that are capable of
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converting lactate to acetate, propionate, or long-chain fatty acids, which can be used
by the cow, declines (Fernando et al., 2010).
In addition to the metabolic, endocrine, and immune system perturbances
experienced by transition dairy cows, they are also likely to experience
environmental/social stressors arising from the normal group changes carried out by
dairy farm management of dry and lactating cows (Talebi et al., 2014). When these
effects are combined with the exertions of parturition, it is not surprising that the period
of highest risk for metabolic and productive disease is the period immediately after
parturition (Horst et al., 1997; Mulligan and Doherty, 2008).
Ingvartsen and colleagues (Ingvartsen et al., 2003) summarized data from
approximately 90,000 primiparous and 60,000 multiparous dairy cows and concluded
that the highest incidence of total diseases, including mastitis, ketosis, digestive
problems, and laminitis, occurred during the first 10 d of lactation. These diseases
create complex problems and can seldom be considered in isolation. Ketosis, fatty liver,
clinical hypocalcemia, retained placenta, metritis and displaced abomasum are all
interrelated (Curtis et al., 1985; Ingvartsen et al., 2003). Because of these inter-
relationships, production diseases of the transition cow regularly result in cascade
effects that increase the incidence of other infectious and/or production diseases that
reduce fertility and reduce milk production (Curtis et al., 1985; Oliver and Sordillo, 1988;
Mulligan and Doherty, 2008). Gröhn et al. (1998) evaluated culling and risk of diseases
in 7,523 Holstein cows. They found that the incidence of the most common seven
diseases in dairy farms were: milk fever 0.9%, retained placenta 9.5%, displaced
abomasum 5.3%, ketosis 5.0%, metritis 4.2%, mastitis 14.5%, and ovarian cysts 10.6.
24
Authors observed that, on average, 30% of the cows that presented one or more of the
diseases were culled before 60 d in milk.
Many nutritional and management strategies of the prepartum transition cow
have been reported to influence the degree of negative energy balance (Overton and
Waldron, 2004; Janovick and Drackley, 2010; Janovick et al., 2011). Moreover, the
decline in DM intake during the last week of gestation tends to initiate a period of
negative nutrient balance (Kunz et al., 1985). Thus, alterations in the nutrition and
management of transition dairy cows have an enormous capacity to alter the health
status, fertility, and productivity of dairy cattle and are ultimately key determinants of
dairy cow welfare and producer profitability (Huntington, 1984; Grant and Albright, 1995;
Mulligan and Doherty, 2008).
Therefore, minimizing depression in DM intake and increasing the nutrient
density of the diet during the transition period (Grant and Albright, 1995) is suggested to
maintain BCS, increase nutrient availability for fetal growth, ease metabolic transition
from pregnancy to lactation, and acclimate rumen microorganisms to lactation diets
(Grummer, 1995; Hayirli et al., 2002; van Saun and Sniffen, 2014)
Transition Period, Energy, and Mineral Metabolism
Nutrient Requirements
In mammals, nutrients are utilized by tissues involved in maintenance and growth
and for establishing body reserves including fatty acid depots as triacylglycerols,
glucose reserves as glycogen in muscle and liver, and amino acid reserves (Bauman
and Currie, 1980). Dry cows require nutrients for maintenance, growth of the conceptus
25
and, perhaps, growth of the dam, particularly if they are initiating their first lactation
(NRC, 2001).
In addition to the normal requirements of the cow, two additional tissues utilizing
a substantial portion of the maternal nutrients are the developing fetus and the lactating
mammary gland. One should not underestimate the importance of partitioning nutrients
to support pregnancy and lactation, because these physiological states are the essence
of survival of the species and, of course, the foundation of the dairy industry (Bauman
and Currie, 1980).
Conceptus and maternal tissues interact throughout gestation such that
pregnancy not only is maintained but that continued development and growth of the
fetus are assured until its delivery from the maternal unit (Thatcher et al., 1980). Fetal
growth from time of conception to birth can be described by an exponential growth
curve, with more than 70% of growth occurring during the last 60 to 70 d of pregnancy
(van Saun and Sniffen, 2014), with the maximal rate of growth occurring at 230 d of
gestation when the fetus is growing 221 g/d (Eley et al., 1978). During this period of
gestation, fetal demands for specific nutrients such as glucose and amino acids are 821
kcal/d and 62 g/d, respectively (Bell et al., 1995). The increased nutrient needs as
gestation progresses places a burden on the dam, especially in the weeks preceding
parturition (van Saun and Sniffen, 2014). This burden imposes a substantial cost to the
animal, because total requirements for nutrients at the end of the pregnancy are about
75% greater than in a non-pregnant animal of the same weight (Bauman and Currie,
1980). Hence, optimal metabolic adaptation is required to avoid the development of
metabolic and infectious diseases.
26
Energy Metabolism
Increased use of glucose and protein by the fetus and uterus generates a shift
from predominate glucose utilization to fat oxidation by maternal tissues, reducing
insulin secretion and tissue sensitivity (Hayirli, 2006) with advancing pregnancy status
facilitating fat oxidation during the last 2 months of pregnancy (van Saun and Sniffen,
2014). It is generally accepted that dairy cows are insulin resistant at the end of
gestation and the beginning of lactation (Sano et al., 1993). These homeorhetic
adaptations are necessary to ensure sufficient glucose supply for the gravid uterus and
lactating mammary gland in support of the growing offspring, prenatally and postnatally
(De Koster and Opsomer, 2013). This period of time is extremely important because a
major decrease in DM intake is also reported (Bertics et al., 1992), and the dependence
on lipid stores increase with a subsequent increase in the probability of metabolic
disorders developing (Doepel et al., 2002).
Glucose is a major energy source for all mammalian cells, and it is the principal
source of energy for the brain (Bell and Bauman, 1997). A constant supply of glucose
must be provided in order to ensure normoglycemia and prevent the potentially
catastrophic effect that hypoglycemia might have on cells of the nervous system (Pilkis
and Granner, 1992). Characteristically, ruminant animals absorb less than 10% of
dietary carbohydrate as hexose sugar (Young, 1977; Lomax and Baird, 1983;
Huntington, 1984), or even have negative portal-drained visceral flux of glucose. In fact,
most carbohydrates digested in the small intestine and converted to glucose are
metabolized by the gut tissues and appear in the portal vein as lactate carbon, which
needs to be converted back into glucose though gluconeogenesis. The ruminant
species have adapted to this lack of dietary glucose by maintaining a constant state of
27
gluconeogenesis (Herdt, 1988). In addition, ruminants conserve glucose by using other
metabolic fuels for most energy needs (Jarrett et al., 1976), particularly short-chain fatty
acids such as acetate and propionate.
Gluconeogenesis is the metabolic sequence that converts carbon substrate such
as propionate, lactate, glycerol, and certain amino acids to glucose, thereby providing
calories to the animal (Hers and Hue, 1983). This process occurs primarily in liver and
to a lesser extent in kidney and serves to assemble small carbon-containing compounds
into a six carbon glucose molecule (Bell and Bauman, 1997). The resulting glucose is
then available for distribution to other tissues in the body for immediate metabolism,
lactose synthesis in the case of mammary tissue, or for storage as glycogen in muscle
or liver or for synthesis of triacylglycerol (Hurley, 1989)
In ruminants, because of the lack of net glucose absorption from the gut (Young,
1977; Reynolds et al., 2003; Huntington, 1984), microbial activity in the rumen is vital,
because the dietary carbohydrate is fermented to short-chain fatty acids, principally
acetate (60 to 70%), propionate (20 to 30%), and butyrate (10 to 15%) (Brockman and
Laarveld, 1986). Propionate produced by ruminal fermentation is the primary substrate
for hepatic gluconeogenesis in the dairy cow in the well fed state, accounting for 60 to
70% of total glucose entry in fed animals (Greenfield et al., 2000; Larsen and
Kristensen, 2009).
The main substrates for glucose synthesis in the liver are propionate, lactate, and
amino acids, especially alanine, accounting for 49.4, 20.6, and 2.7% of the net glucose
release in the prepartum period respectively (Reynolds et al., 2003), and accounting for
80% of the hepatic release of glucose in the first three weeks after calving (Reynolds et
28
al., 2003; Larsen and Kristensen, 2009). Pyruvate is a common entry point in the
gluconeogenic pathway for lactate, alanine and other gluconeogenic amino acids
(Mayes and Bender, 2003).
During gluconeogenesis pyruvate is formed from lactate and alanine in the
cytosol, then is transported to the mitochondria and carboxylated to oxaloacetate by
mitochondrial pyruvate carboxylase (Pilkis and Granner, 1992). In contrast, propionate
is converted through mitochondrial propionyl-CoA carboxylase, methylmalonyl-CoA
mutase, and part of the tricarboxylic acid cycle to oxaloacetate (Aschenbach et al.,
2010). Oxaloacetate can be then metabolized by phosphoenolpyruvate carboxykinase
to phosphoenolpyruvate and further to glucose or serve as an acetyl-CoA acceptor in
the tricarboxylic acid cycle (Mayes and Bender, 2003).
In the adult animal, lipid digestion starts in the rumen by lipolytic microbes, but
the main site of digestion is the small intestine (Garton, 1969). Generally, the intestinal
absorption coefficient of fatty acids ranges from 80% to 92%, with the polyunsaturated
fatty acids having a greater coefficients than the saturated fatty acids (Bauchart, 1993).
Transfer of the free fatty acids to the micellar phase occurs gradually as digesta go
through the intestinal tract (Bauchart et al., 1996). Once in a micelle, fatty acids are
released from particulate matter by a process that involves polar detergency (Bauchart,
1993). Bile secretions in the duodenum favors the interaction of fatty acids with bile
phospholipids and water which leads to the formation of a liquid crystalline phase
(Garton, 1969). With increasing pH, this phase then is dispersed in the presence of bile
salts to form the micellar solution (Bauchart, 1993). Conversion of bile phospholipids to
lysophospholipids by pancreatic phospholipase A2 stimulated micellar solubilization of
29
fatty acids and thus improved the fatty acids passage and absorption by the intestinal
mucosa cells (Contreras et al., 2017). Long-chain fatty acids are then re-esterified to
triacylglycerols and incorporated into chylomicrons and released into lacteals and
eventually into the lymphatic system. Chylomicrons reach the venous circulation and a
portion of the fatty acids are hydrolyzed by lipoprotein lipases in blood vessels and
tissues, but eventually they reach tissues like the liver or mammary gland (Bauchart,
1993). During periods of positive energy balance, adipose tissue stores energy surplus
as fatty acids incorporated into triacylglycerols in a process known as lipogenesis
(Contreras et al., 2017).
During the last three weeks of the dry period, hepatic glucose production is 1.32
kg/d and increases to 3.36 kg/d in the first three weeks of lactation (Reynolds et al.,
2003; Aschenbach et al., 2010). During those final three weeks of gestation, the gravid
uterus consumes 47% of the hepatic glucose production, or approximately 0.62 kg/d
(Leury et al., 1990; Bell, 1995) and the fetus only consumes 8 to 11% of the maternal
glucose production (Reynolds et al., 1986; Sangild et al., 2000). Therefore, the tissues
of the uterus utilize most of the glucose taken up by the gravid uterus, up to 90%, which
represents 36 to 39% of the total hepatic output of glucose. At the same time when
glucose use by the pregnant uterus increases, the supply of gluconeogenic substrates
declines because of reduced DM intake (Bertics et al., 1992); therefore, there is a
reduction in nutrient absorption from the gut (Drackley, 1999), leading to a negative
nutrient balance (Grummer, 1995). In consequence, major shifts occur during this
period. For example, Ha et al. (2017) found major changes in the liver transcriptome
with the onset of lactation. The authors showed an increased expression of pathways
30
closely related to fatty acid oxidation and metabolism, suggesting that nutrients have to
be mobilized from peripheral stores, primarily adipose tissue, to reduce the impact of
less nutrient uptake from the diet (Brockman and Laarveld, 1986; McNamara, 1991).
Energy stores, in the form of adipose tissue triacylglycerols, are mobilized during
times of energy deficit (Koltes and Spurlock, 2011). Triacylglycerol within the adipocyte
lipid droplet are hydrolyzed into NEFA and glycerol by the action of three different
lipases: adipocyte triglyceride lipase, hormone sensitive lipase, and monoglyceride
lipase (Langin et al., 2005). Beta-adrenergic receptors are activated by the binding of
catecholamines. This stimulation results in activation of adenylyl cyclase, which
converts adenosine triphosphate (ATP) to cyclic adenosine monophosphate (AMP;
Koltes and Spurlock, 2011). Increased intracellular concentration of cyclic AMP
activates protein kinase A, which phosphorylates hormone sensitive lipase and perilipin
(Faylon et al., 2014). Phosphorylated hormone sensitive lipase translocates to the lipid
droplet to hydrolyze triacylglycerols to free fatty acids and glycerol (Langin et al., 2005).
Once the triacylglycerol is hydrolyzed resulting in release of NEFA, the latter is
transported in blood bound to albumin (Contreras and Sordillo, 2011). High
concentrations of NEFA in blood have been associated with subsequent milk loss
(Chapinal et al., 2011), increased risks of culling (Roberts et al., 2012), displaced
abomasum (LeBlanc et al., 2005), and metritis (Ospina et al., 2010).
Nonesterified fatty acids are removed from plasma by the liver in proportion to
their concentration and rate of blood flow to the hepatic tissue. In addition, the type of
fatty acid making up NEFA also influences hepatic removal, and between 7 and 25% of
the NEFAs presented to the liver are removed at each pass (Lomax and Baird, 1983).
31
There are several metabolic pathways for the liver to process and dispose of these fatty
acids. They may be secreted in bile, oxidized in the mitochondria either completely to
generate ATP to cells, or partially to generate less ATP, but produce products such as
ketone bodies that can be released to other tissues; completely oxidized to generate
heat and ketones in peroxisomes; or be reesterified to triacylglycerols and either stored
within the cytosol of hepatocytes as lipid droplets or be exported as very-low density
lipoproteins (Emery et al., 1992).
The main reaction of this type available to the liver is the oxidation of fatty acids
to acetyl-coenzyme A followed by the formation of acetoacetate in the mitochondria
(Krebs, 1966). Palmityl transferase I transports long chain fatty acids into the
mitochondria for a complete oxidation or to synthesize ketone bodies (Drackley, 1999).
Nonesterified fatty acids that do not enter the mitochondria for oxidation or conversion
to ketone bodies are reesterified to form triacylglycerols (Herdt et al., 1988). Removal of
these triacylglycerols from the liver requires hydrolysis from the lipid droplets by hepatic
lipase and incorporation with cholesterol, cholesteryl esters, phospholipids, and
apolipoproteins for synthesis and secretion as very low-density lipoproteins, the carrier
of triacylglycerols in blood after export from the liver (Contreras and Sordillo, 2011).
Once incorporated into very low-density lipoproteins and secreted into the blood, fatty
acids contained in triacylglycerols can be used by various tissues for energy or
transported to the mammary gland for synthesis of milk fat (Herdt, 1988). Herdt et al.
(1988) demonstrated that fasted sheep developed fatty liver during a period of high
NEFA uptake by the liver, without a corresponding increase in serum lipoprotein
concentration. The inability to secrete lipoproteins in proportion to the uptake of fatty
32
acids by the liver demonstrates that ruminants are not very efficient in exporting fat as
lipoproteins resulting in extended storage of triacylglycerols in the hepatic tissue (Herdt,
1988).
Mineral Requirements
Minerals are inorganic nutrients, usually required in small amounts (Soetan et al.,
2010). Some are essential for normal growth and reproduction of animals (NRC, 2001).
Before an element can be classified as essential, it is generally considered necessary to
prove that purified diets lacking the element cause deficiency symptoms in animals and
that those symptoms can be eradicated or prevented by adding the element to the
experimental diet (McDonald et al., 2011). Those required in large quantities are
referred to as macrominerals and this group includes calcium, phosphorus, sodium,
chloride, potassium, magnesium, and sulfur. In general, their concentration in a diet is
expressed on the basis of percentage of the diet or in grams per kilogram of diet (Goff,
2015b). Those elements required in milligrams or micrograms are referred to as the
trace minerals, and they include cobalt, copper, iodine, iron, manganese, molybdenum,
selenium, zinc, and perhaps chromium and fluorine (NRC, 2001). Minerals perform four
broad types of functions in animals: 1) form structural components of body organs and
tissue (Nordin, 1998), 2) act as electrolytes responsible for regulating osmotic pressure,
acid-base balance, membrane permeability and nerve impulses (Ebashi and Endo,
1968; Ebashi, 1985; Hu and Murphy, 2004), 3) act as catalysts in enzyme and
endocrine system (Evans and Sorger, 1966; de Carvalho et al., 2010), and 4) regulate
cell activation, replication, and differentiation (Krueger et al., 1977; Grafton and Thwaite,
2001; Lewis, 2001).
33
Mineral requirements of livestock are influenced by factors such as species or
breed, age, gender, physiological condition, production rate, body weight, and
environmental conditions (NRC, 2001). Requirements can be estimated by feeding
groups of livestock with diets providing a range of mineral intakes above and below pre-
defined minimum values followed by measuring responses for a relevant variable such
as growth rate or blood composition (Suttle, 2010).
Calcium. Extracellular calcium is essential for formation of skeletal tissues,
transmission of nerve impulses, excitation of skeletal and cardiac muscle contractions,
blood clotting, and of milk production (Goff, 2015a). About 99% of Ca is found in the
skeletal tissue, 0.9% in the cell membrane, 0.1% in the extracellular fluid, and in
extremely low concentrations in the cytosol (Rosol et al., 1995).
Although there is some evidence that calcium absorption by sheep and goat
occurs mainly pre-duodenally (Braithwaite, 1976; Schröder and Breves, 2006), there is
not enough information to know where it exactly happens in cattle. Intestinal absorption
is proportional to dietary intake of Ca. Low calcium diets are associated with high
absorption rates, with up to 95% of calcium intake absorbed, whereas high calcium
diets result in absorption rates of about 30% (Rosol and Capen, 1997). Calcium can be
absorbed in the small intestine by a paracellular passive transport system or it can be
actively transported across the enterocyte transcellularly, depending on the amount of
calcium reaching the gut (Goff, 2015a). Calcium is absorbed from the digesta by an
active process in the small intestine under the control of two hormones: parathyroid
hormone and the physiologically active form of vitamin D3, 1,25-dihydroxycholecalciferol
(1,25-(OH)2D3, also known as calcitriol) (Suttle, 2010). It can also be absorbed by a
34
passive transport process between epithelial cells across any portion of the digestive
tract whenever ionized calcium in the digestive fluids directly over the mucosa exceeds
6 mM (Bronner, 1987). After calcium enters the cytoplasm, it is transported by the
vitamin D-dependent calcium binding protein and transferred across the cell (Feher,
1984), or by calmodulin, which is not vitamin D-dependent (Bronner, 1987). Once in the
basolateral membrane, calcium will have to exit the enterocyte against its concentration
and electrical gradient (Horst, 1986). Calcium is transported by another vitamin D-
dependent mechanism, the calcium/sodium exchange adenosine triphosphatase pump
(Rosol et al., 1995). The pump uses the energy in adenosine triphosphate and the
electrochemical force provided by allowing 3 sodium ions into the cell to drive a calcium
atom into the extracellular fluid against a nearly 5000‐fold difference concentration
gradient, (Goff, 2015a). Then, a small portion of the Ca in the extracellular fluid is
transported into the plasma Ca pool (Reinhardt et al., 1988). Calcium deposition in the
bone varies, but in cows from three weeks prepartum until calving it averaged 9.1 g/d
(Ramberg et al., 1970). Calcium excretion in urine and feces prepartum averaged 0.7
and 6.4 g/d respectively (Ramberg et al., 1970), and excretion in milk during lactation is
from 20 to 80 g/d because of the high calcium secretion in milk (Reinhardt et al., 1988).
The amount of Ca that needs to enter the extracellular compartment in a
transition mature cow is 0.0154 g/kg of body weight for maintenance (NRC, 2001), plus
another 2.3 g of calcium/d at 190 d of gestation or 10.3 g of calcium/d at 280 d of
gestation for uterine and fetal tissue accretion (House and Bell, 1993). For a lactating
cow, maintenance calcium requirements increase to 0.031g of calcium/kg of body
weight, and the absorbed calcium required/kg of milk produced is 1.22 g for Holstein
35
cows, 1.45 g for Jersey cows, and 1.37 g for other breeds. Cows require about 2.1 g of
absorbed calcium/kg of colostrum produced (NRC, 2001).
Phosphorus. Most of the phosphorus found in the body is combined with oxygen
to form the phosphate anion (Goff, 2015b). Around 80% is present in the bones and
teeth along with calcium and the remaining 20% is in soft tissues and fluids (Suttle,
2010). It is found in every cell of the body and almost all energy transactions involve
formation or breaking of high energy bonds that link oxides of phosphate to carbon or to
carbon-nitrogen compounds (Evans and Sorger, 1966; Dennis, 1996). Phosphorus is
also involved in acid-base buffer systems of rumen fluid and blood, in cell differentiation,
and is a component of cell walls and cell content as phospholipids (Soetan et al., 2010).
It is also needed by ruminal microorganisms for digestion of cellulose (Komiscarczuk et
al., 1987) and synthesis of microbial protein (Stern and Hoover, 1979).
Phosphorus is primarily absorbed in the small intestine (Grace et al., 1974), and
the uptake of phosphorus into the ruminant duodenal brush-border membrane vesicles
is by 1) a hydrogen/phosphorus cotransport mechanism (Shirazi-Beechey et al., 1996)
that is only produced in the enterocytes upon stimulation by calcitriol (Goff, 2015a) and
2) by passive diffusion (Rosol and Capen, 1997). Diffusion occurs because dietary
phosphate can cause intraluminal phosphate concentrations to be considerably greater
than the extracellular concentration (0.8 mmol/L) (Goff, 2015a). Large amounts of
phosphate, equivalent to 60 to 80% of dietary phosphate does manage to cross the tight
junctions and enter the extracellular fluid (Reinhardt et al., 1988). Intestinal phosphorus
absorption efficiency can be upregulated during periods of phosphorus deficiency as
renal production of calcitriol is directly stimulated by very low plasma phosphorus (Goff,
36
2015b). True absorption of phosphorus ranges between 80 and 85% (Martz et al., 1990;
NRC, 2001). It then exits the cytosol on the basolateral membrane by passive diffusion
(Dennis, 1996)
Plasma content of phosphorus are in the range of 1 to 2 g, and the extracellular
fluid has a phosphorus content of 4 to 7 g (Quiroz-Rocha et al., 2009). They are well
correlated with dietary phosphorus absorption (Rosol and Capen, 1997). Phosphorus
absorbed in excess of needs is excreted in feces at 50 to 60 g/d (Morse et al., 1992;
Brintrup et al., 1993), in urine at 2 to 12 g/d, in milk at 10 to 70 g/d, and in saliva at 30 to
90 g/d (Reinhardt et al., 1988). Salivary phosphorus secretions supply rumen microbes
with a readily available source of phosphorus, and this appears necessary for cellulose
digestion (Komiscarczuk et al., 1987). Most, but not all, of the salivary phosphorus
secreted is recovered by intestinal absorption (Breves and Schröder, 1991). Whatever
is not reabsorbed is excreted in feces (Goff, 2015a). About two-thirds or more of
phosphorus in cereal grains, oilseed meals, and grain by-products is bound organically
in phytate (NRC, 2001). Ruminal microbes are able to digest phytic acid so that nearly
all the phytate‐bound phosphorus, is available for absorption by ruminants (Morse et al.,
1992; Goff, 2015b).
The requirements of phosphorus during the dry period are 1.0 g/kg of dietary dry
matter consumed for maintenance (NRC, 2001) and 1.9 g/day at 190 days of gestation
and increases to 5.4 g/day at 280 days of gestation for fetal accretion (House and Bell,
1993). In lactating cows, the requirement for absorbed phosphorus is calculated by
multiplying the milk yield in kg/d by 0.9. Therefore, a cow producing 50 kg of milk a day
37
should consume 45 g of absorbed phosphorus per day to supply the needs for milk
synthesis (NRC, 2001).
Magnesium. The body of ruminants contains 0.05% magnesium by weight, of
which 60% is in the skeleton, 38% in the soft tissue, and 1 to 2% in the extracellular
component (Rosol and Capen, 1997). Although 60 to 70% of the body’s magnesium is
present in the skeleton, magnesium is second only to potassium in abundance in the
soft tissues, which contain 0.1 to 0.2 g/kg of fresh tissue (Suttle, 2010). The
concentration of magnesium inside the rumen epithelial cells is 0.5 to 1.2 mM and it is
kept within these narrow limits in spite of wide changes in magnesium concentration in
the ruminal digesta (Martens and Schweigel, 2000). Magnesium is associated
predominantly with the microsomes, where it functions as a catalyst of a wide array of
enzymes, something like 300 (Martens and Rayssiguier, 1980), facilitating the union of
substrate and enzyme by first binding to one or the other (McDonald et al., 2011).
Magnesium is thus required for oxidative phosphorylation leading to adenosine
triphosphate formation (Ko et al., 1997; Ko et al., 1999), an important co-factor in the
machineries that replicate, transcribe, and translate genomic information (Hartwig,
2001). As a structural co-factor, magnesium stabilizes the ribosome, lipid membranes,
and nucleic acids (Beaven et al., 1990).
Plasma magnesium concentration in mammals is normally 0.75 to 1.0 mmol/L or
1.8 to 2.4 mg/dL (Romani and Scarpa, 1992). Like calcium, a reduction in extracellular
magnesium reduces the nerve membrane potential closer to the threshold for an action
potential to occur (Rosol and Capen, 1997). Also, an increase in the ratio of calcium to
38
magnesium at the myoneural junction increases the release of acetylcholine into the
myoneural junction (Goff, 2015b), in order to activate the muscle to contract.
The principal site of magnesium absorption is the reticulum-rumen before the
pylorus, and approximately 20 to 30% of the dietary magnesium is absorbed in those
sites (Tomas and Potter, 1976). Absorption occurs principally by a passive process and
is, therefore, dependent on the concentration of magnesium ions in the digesta (Goff,
2015b). An active carrier-mediated process possibly involving a magnesium and
hydrogen ion exchanger and insensitive to potassium becomes the dominant process at
high luminal magnesium concentrations (Martens and Rayssiguier, 1980). Magnesium
absorbability can be low and potassium reduces the apparent digestibility by 0.075 for
every percentage unit of potassium in the diet (Weiss, 2004). Potassium inhibits the two
active transport systems in the rumen wall that carry magnesium against the
electrochemical gradient (Care et al., 1984; Wylie et al., 1985). Magnesium solubility is
sharply reduced when rumen pH rises above 6.5 (Goff, 2006). Magnesium absorption is
completed by a secondary active process located in the basolateral membrane that is
saturable and controls efflux to the bloodstream (Suttle, 2010).
Magnesium is less readily filtered at the glomerulus than most macro-minerals,
but sufficient amounts are filtered and escape tubular reabsorption once the renal
threshold of 0.92 mmol/L is exceeded. Therefore, urinary excretion is a major route of
disposal of absorbed magnesium resulting in 0.5 to 5 g/d (Martens and Schweigel,
2000). Endogenous fecal loss and salivary loss of magnesium are calculated to be 1 to
1.5 g/d and 0.5 to 1.0 g/d, respectively (Reinhardt et al., 1988).
39
The daily requirement of absorbable magnesium is 3 mg/kg of body weight
(NRC, 2001) and 0.33 g/d for fetal tissue accretion (Reinhardt et al., 1988). During
lactation the cow requires an extra 0.12 to 0.15 g/kg of milk produced (NRC, 2001).
Sodium. Sodium is the primary extracellular cation (Soetan et al., 2010) and,
along with chloride and potassium in proper concentrations and balance are
indispensable for a number of important physiologic functions. It modulates extracellular
fluid volume and acid-base equilibrium (Suttle, 2010). Additionally, heart function and
nerve impulse conduction and transmission are dependent on the proper balance of
sodium and potassium (McDonald et al., 2011). It also plays an indispensable role in the
sodium-potassium adenosine triphosphate enzyme and the sodium-potassium pump
essential for nutrient and mineral transportation in the cell (Goff, 2015b). The sodium-
potassium pump is essential for all eukaryotic cells, enabling transport of glucose,
amino acids, and phosphate into cells, and ions out of cells (Kaplan, 2002). Sodium also
is a major component of salts in saliva to buffer acid from microbial fermentation in the
rumen (Erdman, 1988).
Absorption occurs throughout the digestive tract, and dietary sodium generally is
assumed to be almost completely available (Warner and Stacy, 1972; NRC, 2001). The
transport of sodium and chloride ions is active and in the direction from lumen to the
blood, this indicates that some of the sodium is transported by an exchange or
cotransport (sodium-chloride) mechanism (Diernaes et al., 1994). Digestibility of sodium
ranges from 75 to 91% (Gaebel et al., 1987; NRC, 2001); blood concentration of sodium
ranges from 132 to 152 mM (Coppock et al., 1982). Sodium excretion in urine, feces,
40
and milk are, respectively, 42.9 g/d, 13.4 g/d, and 10.0 g/d in the dairy cow (Bannink et
al., 1999). In urine, excretion can increase or decrease according to total dietary intake.
The daily maintenance requirement for absorbed sodium for non-lactating
pregnant cows is approximately 1.5 g/100 kg of body weight, but it changes depending
on ambient temperature because of increased loss through sweating (NRC, 2001).
During pregnancy, sodium requirements for fetal tissue accretion is approximately 1.4
g/day from 190 to 280 d of gestation (House and Bell, 1993). For a lactating cow, the
sodium requirement per kilogram of milk produced is 0.63 g/d.
Chloride. It is the major anion in the body involved in the regulation of osmotic
pressure; it makes up to 60% of the anions in the extracellular fluid (Soetan et al.,
2010). It is essential for transport of carbon dioxide and oxygen by red blood cells (Goff,
2015b). Chloride also is the chief anion in gastric secretions for protein digestion, and it
is needed for activation of pancreatic amylase (Suttle, 2010). It has a close relationship
with sodium and potassium to maintain a strong ion difference of body fluids (Constable,
1999).
Dietary chloride is absorbed with at least 80% and closer to 100% efficiency
(Goff, 2015b). It is generally accepted that chloride is transported across the intestinal
tract epithelium of ruminants in the mucosal-serosal direction by an active transport
mechanism (Martens and Gabel, 1988). The active transport of sodium and chloride is
coupled, they are co-transported to maintain electrical balance (Martens and Blume,
1987). Bicarbonate has also a role in chloride absorption, with part of the bicarbonate
secretion being dependent on luminal chloride, and result from chloride-bicarbonate
exchange (Hopfer and Liedtke, 1987). Chloride is released into the serosal surface by
41
the action of the chloride potassium co-transporter, the chloride pump, and the sodium-
chloride pump, the last two at the expense of an energy molecule (Goff, 2015a).
Concentrations of chloride in blood range between 100 and 113 mmol/L
(Coppock et al., 1982). Concentrations above those result in renal excretion of chloride
ions to maintain acid–base balance in the animal (Goff, 2015b). Urinary excretion of
chloride ranges from 40 to 80 g/d depending on the intake of chloride. Milk losses of
chloride depend on yield and range from 1.2 to 1.4 g/L. Fecal losses range from 16 to
32 g/d (Silanikove et al., 1997; NRC, 2001).
The daily requirement of chloride for maintenance is 2.25 g/100 kg of body
weight and for pregnancy is estimated at 1.0 g/day from 190 d of gestation to calving. In
lactating cows, an extra 1.15 g/kg of milk is required (NRC, 2001).
Potassium. Is the third most abundant mineral in the body, and is the major
intracellular cation (Soetan et al., 2010). It has to be supplemented because there is
very little storage in the body and it has the highest requirement of all mineral cations
(NRC, 2001). Extracellular potassium concentration is normally 3.9 to 5.8 mmol/L and it
plays a vital role in osmotic equilibrium and maintenance of acid–base balance (Goff,
2015b).
Intracellular potassium concentration is 150 to 160 mmol/L, and it is a co-factor of
enzymes involved in protein synthesis and carbohydrate metabolism (Suttle, 2010). The
ratio of intracellular to extracellular fluid potassium concentration is the main
determinant of resting cell membrane potentials, which affects nerve and muscle cell
excitability (McDonald et al., 2011).
42
Absorption of potassium occurs across the tight junctions and potassium moves
between cells directly into the extracellular fluid, particularly in the lower small intestine
(Goff, 2015a). Dietary sources of potassium are highly soluble, and the apparent
absorption of potassium is estimated between 0.85 to 0.95 (Suttle, 2010). The kidneys
are the major regulators of potassium concentration in blood and excrete any excess
absorbed potassium in urine. Urinary excretion of potassium is about 0.038 g/kg of body
weight, and endogenous fecal losses are approximately 6.1 g of potassium/kg DM
ingested. Milk potassium secretion is approximately 1.5 g of potassium/kg of milk
produced (Goff, 2006). It has been calculated that urinary potassium represents 86% of
the total potassium output for nonlactating cows and 75% of lactating cows, with 13% of
the daily excretion of potassium represented by fecal losses and 12% secreted in milk
(Ward, 1966).
The requirement of daily absorbed potassium for a non-lactating pregnant cow is
0.038 g/kg of body weight plus 2.6 g/kg of dietary DM intake (NRC, 2001). Pregnancy
requirements for fetal/uterine tissue accretion is estimated at 1.0 g/day from 190 d of
pregnancy to calving.
Sulfur. About 0.15% of the body weight is sulfur, and its functions are as diverse
as the proteins of which it is a part (NRC, 2001). Sulfur is frequently present as highly
reactive sulfhydryl groups or disulfide bonds, maintaining the spatial configuration of
elaborate polypeptide chains and providing the site of attachment for prosthetic groups
and the binding to substrates that are essential to the activity of many enzymes (Suttle,
2010). Hormones such as insulin and oxytocin contain sulfur, as do the vitamins thiamin
and biotin (McDonald et al., 2011). The oxidation of methionine and cysteine causes
43
sulfur to also exist in tissues as the sulfur anion, which influences the acid-base balance
of the animal (Goff, 2015b). It is present as sulfate in the chondroitin sulfate of
connective tissue, and is particularly abundant in the keratin-rich appendages (Soetan
et al., 2010). Cattle tissues cannot synthesis methionine, thiamin, and biotin, among
other nutrients. These must either be supplied in the diet or synthesized by ruminal
microbes (Soetan et al., 2010). Sulfur incorporated into microbial protein is absorbed
from the small intestine as cysteine and methionine (NRC, 2001).
The dietary requirements of sulfur for the cow is primarily to provide adequate
substrate to ensure maximal microbial protein synthesis. Dietary concentrations of
0.12% sulfur would approximate sulfur balance and 0.18% sulfur would allow for a
mean positive balance of 4 g of sulfur daily in cows producing between 8 and 37 kg of
milk (Bouchard and Conrad, 2003). The daily sulfur requirement for maintenance and
pregnancy is 0.20% of dietary DM intake (NRC, 2001).
Calcium
Calcium is the fifth most abundant mineral in the human body, with around 1000g
present in human adults (Peacock, 2010). It is present in three forms: 1) the active or
ionized form, 2) protein bound or inert, and 3) as salts in combination with citrate,
lactate or phosphate (Malhorta, 2012).
The majority of the calcium of the body (99%) is present in the inorganic matrix of
bone as hydroxyapatite (Suttle, 2010), and most of the remaining calcium (0.9%) is
sequestered in the plasma membrane and endoplasmic reticulum of cells (Favus and
Goltzman, 2013). Extracellular fluid contains 0.1% of the body’s calcium mass with a
total calcium concentration of about 2.3 to 2.5 mmol/L in adult mammals and with
44
slightly higher values in the young (Goff, 2015b). Approximately 50% of the extracellular
Ca, or approximately 1.20 mmol/L is present in the ionized form which is the biologically
active form of calcium, whereas 40% is bound to albumin, and the remaining 10% exists
as a complex of either citrate, lactate or phosphate salts (Favus and Goltzman, 2013).
The protein-bound fraction of calcium is principally bound to negatively-charged sites on
albumin with smaller amounts bound to globulins (Rosol et al., 1995). The protein-
bound form of calcium is dependent on serum pH (Odom et al., 1986). As the pH of
blood becomes more acidic, the ionized calcium concentration will increase caused by
the competition of hydrogen for binding to the negatively-charged sites on plasma
proteins (Wang et al., 2002). The ionized and complexed calcium compose the
ultrafilterable fraction of calcium and represent the fraction that is present in the
glomerular filtrate (Peacock, 2010).
Calcium serves two primary functions in the body: 1) structural in bones and
teeth; and 2) as a messenger or regulatory ion (Jaiswal, 2001). It is essential for the
formation of skeletal tissues (Bender and Mayes, 2003) and to provide rigidity to it by
virtue of the insoluble salts it forms with phosphoric acid (Nordin, 1998). This rigidity is
provided by a particular insoluble calcium salt analogous to the mineral hydroxyapatite
but also containing a small component of calcium carbonate (Termine and Posner,
1967). The calcium salts do more than provide rigidity to the skeleton, they also
constitute a very large reservoir of calcium for the maintenance of the precise
concentration of the ionized calcium (1.2 mmol/L) in the extracellular fluid (Nordin,
1998). The protection of this critical concentration by parathyroid hormone (PTH) and
vitamin D (Bender and Mayes, 2003) reflects the vital role of calcium on the excitability
45
of the presynaptic nerve, on the release of transmitter, and on the postsynaptic
elements (Rubin, 1970), in regulation of the cardiac and skeletal muscle contraction
(Ebashi, 1985; Somlyo et al., 1985), and in enzyme mediated reactions. Hidaka et al.
(1980) showed that the adenosine triphosphatase activity of chicken gizzard actomyosin
was dependent on calcium. Calcium also is important in blood clotting, for maintenance
of an electrolyte balance suitable for the interaction of the plasma colloids (Lovelock and
Porterfield, 1952), and as major component in milk (NRC, 2001).
Calcium has vital functions within cells in all living creatures, predominantly as a
second messenger transmitting signals between the plasma membrane and the
intracellular machinery (Power et al., 1999). At least 95% of intracellular calcium is
bound to macromolecules such as proteins and nucleic acids, and it is contained in
intracellular organelles such as the nucleus, endoplasmic reticulum, and mitochondria
(Kinder and Stewart, 2002). Cells maintain a steep transmembrane gradient for calcium,
with the extracellular ionized calcium concentration of 1.0 to 1.3 mmol/L (Nordin, 1998),
10,000 times greater than the free, resting intracellular calcium concentration of 100
nmol/L (Clapham, 1995). The plasma membrane is relatively impermeable to calcium,
but the membrane pumps counteract the small passive leak of calcium into the cell
down the electrochemical gradient (Kinder and Stewart, 2002). The presence of this
transmembrane gradient permits the cell to use calcium as an intracellular messenger
that carries the information transported by hormones and neurotransmitters into the
interior of the cell (Brini and Carafoli, 2000; Stewart et al., 2015).
Serum calcium concentrations can vary slightly caused by several reasons, some
of which minor health consequences. In contrast, serum ionized calcium (iCa)
46
concentration is tightly regulated and is, therefore, the clinically important parameter to
measure (Peacock, 2010), although more difficult to do so. Minor changes in
concentrations of iCa can have marked effects on cell metabolism. Therefore, calcium
homeostasis is largely regulated through an integrated hormonal system that controls
calcium transport in the gut, kidney, and bone (Suttle, 2010). The major hormones that
are responsible for normal calcium homeostasis are PTH and 1,25-dihydroxyvitamin D;
these hormones control extracellular fluid calcium on a chronic basis (Mundy and Guise,
1999), and keep the calcium concentration within fairly narrow ranges by regulating the
absorption, excretion, and redistribution of calcium and other minerals by the body
(Goff, 2015b).
Calcium Metabolism
Calcium Absorption
Calcium like other minerals must be in solution if it is to cross the intestinal tract
and enter the blood (Alpers, 2013). Fortunately, the acids of the abomasum permit
much of the inorganic dietary calcium to become solubilized (Ward et al., 1979).
The efficiency of calcium absorption is affected by the intraluminal presence of
dietary components, and by the calcium and vitamin D status of the animal. Manston
(1967) showed that by increasing phosphorus intake from 100 g to 280 g, calcium
absorption increased 9% in the cow. In the same study Manston (1967) showed an
increase of 11% in calcium absorption when calcium intake increased from 430 to 620
g. Absorption also depends on physiological state such as growth, age, pregnancy, and
lactation (Allen, 1982). For example, Hansard et al. (1954) measured calcium
absorption in Hereford cattle at different ages by feeding radiolabeled calcium. The
47
authors found that the group of 10-d old calves retained 98% of the calcium, whereas
the 6-month old group only retained 38% and the mature group only 16%. It is thought
that an age-dependent decline in the number of vitamin D receptors in the intestinal
cells of the bovine influence calcium absorption as the animal becomes older (Horst et
al., 1990).
Diet also plays a role in the amount of calcium the cows absorbs. Martz et al.
(1990) showed that lactating cows fed a diet composed mostly of alfalfa absorbed 18%
less calcium than cows fed a diet composed of a mixture of alfalfa and corn silage. van’t
Klooster (1976) compared cows in different physiological states and showed that those
lactating had 30% greater absorption when compared with dry cows, and the latter had
an increase of 13% in calcium absorption as they approached parturition.
Although there is some evidence that calcium absorption by small ruminants
occurs mainly pre-duodenally (Braithwaite, 1976; Schröder and Breves, 2006), there is
not enough information to know where it exactly happens in cattle. Soluble dietary
calcium can cross the foregut and gastrointestinal epithelium by two mechanisms. The
first involves the active transport of calcium across intestinal epithelial cells primarily in
the duodenum and jejunum by a process that depends on the stimulation of the
epithelial cells by calcitriol (Christakos, 2012). The second mechanism is by a passive
nonsaturable calcium movement that involves calcium concentration and electrical
gradient. The lumen of the intestinal tract always has greater concentration than the
cytosol, which is only 0.0002 mmol/L, so calcium moves across the apical membrane
down its concentration and electrical gradients (Bronner, 1987).
48
Active calcium transport is vitamin D dependent and it requires influx of calcium
into intestinal epithelial cells via calcium channels, movement and buffering into the
cytoplasm, and basolateral exit by a calcium-adenosine triphosphatase (Rosol and
Capen, 1997). Vitamin D is a steroid hormone synthesized in the skin of the cow
following irradiation by the ultraviolet B rays of the sun (Holick, 2008) or supplied in the
diet as vitamin D2 or vitamin D3 (Horst et al., 1981). Vitamin D3 produced in the skin is
inactive, so it is later transported through the bloodstream by the vitamin D binding
protein to the liver where it undergoes hydroxylation to form 25-hydroxyvitamin D3
(Horsting and DeLuca, 1969). After the 25-hydroxyvitamin D3 is formed, it is transported
to the kidney, where a second hydroxylation occurs and is converted to the bioactive
form 1,25-dihydroxyvitamin D3 (Fraser and Kodicek, 1970). The active form then
diffuses into the target cells and interacts with its receptor, the vitamin D receptor,
located predominantly in the cell nucleus (Hunziker et al., 1982). Vitamin D receptor is
found in virtually all epithelial cells of the gastrointestinal tract, where it initiates
transcription and translation of genes necessary for the active transport of dietary
calcium across the epithelial cells (Wasserman and Fullmer, 1995).
The first obstacle to active calcium transport is moving the calcium across the
apical membrane of the cells, because intracellular ionized calcium concentrations are
extremely low (Goff, 2015a). The concentration difference between the gut and the
intracellular fluid of the epithelial cells creates an electrochemical gradient that would
drive calcium across the membrane if it were freely permeable to calcium (Goff, 2014).
However, the cell membrane is not freely permeable to calcium. One function of 1,25-
dihydroxyvitamin D is to stimulate the production of apical membrane calcium channel
49
proteins, such as the transient receptor potential cation channel, subfamily V protein
(Fleet and Schoch, 2010). Opening the TRPV-6 channel allows calcium to reach the
cytosol. Now the calcium comes bound to a second vitamin D-dependent protein known
as calbidin-9KD (Van De Graaf et al., 2004). This calcium binding protein carries the
calcium across the cell cytosol to the basolateral membrane of the epithelial cell
(Bronner et al., 1986). Because the concentration of calcium is less than the
extracellular fluid, it is necessary to pump calcium out of the cell against its
electrochemical gradient. This process is achieved by using a third vitamin D-dependent
protein, a plasma membrane calcium-adenosine triphosphatase pump, that uses energy
in adenosine triphosphate to pump calcium into the blood, or by a sodium/calcium
exchanger pump (Christakos, 2012).
A second vitamin D independent mechanism of calcium absorption known as
paracellular calcium transport involves the movement of calcium from the lumen to the
extracellular fluids between intestinal epithelial cells (Favus and Goltzman, 2013) and is
driven purely by the concentration of soluble calcium reaching the epithelial cells
(Wasserman and Fullmer, 1995). When ionized calcium concentration is in proximity to
the tight junctions of epithelial cells and significantly exceeds the ionized calcium in the
extracellular fluids, calcium flows across the tight junctions directly into the extracellular
fluid and blood to equilibrate calcium concentrations on both sides (Bronner, 1987;
Christakos, 2012).
Calcium Homeostasis
Calcium homeostasis is primarily controlled by the parathyroid glands, which are
extremely sensitive to a decline in blood ionized calcium concentration and respond to it
50
by secreting PTH (Mundy and Guise, 1999). The parathyroid cells can determine the
extracellular ionized calcium concentration using calcium sensing receptor molecules
located in the surface of the parathyroid cells, which have the ability to bind ionized
calcium in the millimolar range (Brown, 2007). Whenever ionized calcium in the
extracellular fluid decreases below the normal concentration, approximately 1.0 to 1.2
mmol/L, PTH is secreted in large amounts (Goff, 2014).
Parathyroid hormone has two major calcium-elevating actions. The first one is to
enhance renal reabsorption of calcium from proximal renal tubular fluids. Widrow and
Levinsky (1962) showed that the application of a synthetic PTH induced hypercalcemic
responses, and decreased calcium urine excretion in dogs and mice, respectively.
Commonly the urine calcium excretion is low, but if the perturbation in calcium levels is
small. Reducing the urinary calcium loss may be all that is required to restore the blood
calcium concentrations (Goff et al., 1986). The second action that PTH performs is to
stimulate synthesis of 1,25 dihydroxyvitamin D and the mobilization of calcium stored in
bones. Such mechanisms bring large amounts of calcium into the blood to control
abrupt changes in blood calcium content (Rosol and Capen, 1997). Calcium exists in
bone in two forms that can contribute to calcium homeostasis. The bulk, 99%, of
calcium in the skeleton is found within the hydroxyapatite crystals bound to the collagen
matrix (Suttle, 2010). Calcium within these crystals can only be mobilized by
osteoclasts, which are stimulated after the interaction of PTH with neighboring cells, the
osteoblasts. Once active, the osteoclasts secrete enzymes and acid to digest the
collagen matrix (Mannstadt et al., 1999). This action liberates the calcium from the
crystals for return to the blood (Goff, 2014).
51
A smaller, but still critical amount of calcium is in the solution within the lacunae
surrounding each osteocyte and the small channels connecting osteocytes within the
bone (Rosol and Capen, 1997). This calcium is readily mobilized, and the osteocytes
lining this compartment respond within minutes to PTH by pumping calcium into the
extracellular fluid (Teti and Zallone, 2009). Calcium abandons the extracellular fluid to
be incorporated in bone, excess is excreted in urine with daily amounts of 0.2 to 6 g,
and 5 to 8 g of endogenous calcium excreted in feces, small quantities secreted in
sweat, and 1.2 to 1.4 g secreted in each L of milk (Ramberg et al., 1970).
The kidneys reabsorb 98% of the calcium present in the filtrate by either active or
passive mechanisms occurring at many sites along the nephron (Costanzo and
Windhager, 1978). Approximately 60% of the filtered calcium is reabsorbed in the
proximal tubule, where the absorption is almost entirely passive. Calcium is also
absorbed in the Henle’s loop passively, but in this site only 20% of the filtrate is
reabsorbed. Finally, small but critical fractions of calcium, 3 to 10% of the filtrate, is
reabsorbed in the distal nephron (Friedman and Gesek, 1995).
The beginning of lactation in the dairy cow creates a sudden demand for large
quantities of calcium. Colostrum is especially rich in calcium as compared with that in
milk secreted a few days later (Littledike, 1976). Therefore, metabolism of calcium by a
lactating dairy cow has to adapt to the increased demands of 20 to 30 g/d as a function
of milk secretion (McGrath et al., 2016). Secretion of Ca in colostrum and milk can be 4-
fold greater than the calculated fecal metabolic loss of calcium by the cow. The
functioning udder has been shown to be the cause of the drastic decrease in calcium
content of the blood at the initiation of lactation (Swanson et al., 1956).
52
Milk calcium exists in bound and ionized forms. Bound calcium is associated both
with casein micelles and complexed to citrate and phosphate. Ionized calcium in milk is
1 to 4 mM, at least 1000 times its concentration in the mammary alveolar cell. For this
reason, active transport mechanisms are necessary for transfer of calcium to the lumen
of the mammary alveolus (Holt, 1981; Neville and Watters, 1983). Milk proteins are
secreted via the exocytosis of vesicles derived from the Golgi apparatus. Because a
large proportion of calcium in most milks is bound within the casein micelle, it is likely
that most of the calcium also is secreted via exocytosis (Neville and Watters, 1983). A
calcium-stimulated adenosine triphosphatase has been found in the Golgi membrane
fraction of bovine mammary gland homogenates. The calcium dependent adenosine
triphosphatase generates a gradient in ionized calcium between the inside of the Golgi
vesicle and cytosol and further accumulation of calcium results from formation of
complexes with citrate, orthophosphate, and casein (Holt, 1981).
Hypocalcemia
Clinical hypocalcemia is commonly known as milk fever, which is a nonfebrile
disorder of adult dairy cows in which acute calcium deficiency causes progressive
neuromuscular dysfunction with flaccid paralysis, circulatory collapse, and depression of
consciousness (Oetzel, 1988). It is a metabolic disorder and is closely related to the
onset of lactation (Boda and Cole, 1956) because synthesis and secretion of colostrum
impose major loses of calcium equivalent to 7 to 10 times (20 to 30 g secreted) the
amount of calcium present in blood (Horst et al., 2005). Goff et al. (2002) showed that
by performing a mastectomy at least one month before parturition, they abolish the
decline in blood concentrations of calcium at calving, thereby proving that the decrease
53
in blood calcium is strictly related to synthesis and secretion of colostrum and milk.
Therefore, hypocalcemia occurs because the mammary gland’s demand for calcium at
the onset of milk production draws calcium from the plasma and extracellular fluid pools
faster than it can be replaced (Goff et al., 2014).
Hypocalcemia is classified as clinical or subclinical depending on the severity of
the changes in blood calcium and the clinical signs presented by the cow (Oetzel,
2013). Clinical hypocalcemia usually presents blood plasma concentrations of calcium
below 1.5 mM and the cow presents the typical clinical signs with recumbency, muscle
weakness, and flaccid paralysis (Larsen et al., 2001). It affects about 5% of all the dairy
cows within 1 or 2 d of calving, with up to 10% of older cows presenting the disease
(Reinhardt et al., 2011), and the incidence increases as parity increases (Curtis et al.,
1984). Clinical hypocalcemia can be divided into three phases. Stage one, cows present
no recumbency and may go unnoticed because its signs are subtle. Affected cattle
appear to be excitable, nervous, and weak. Cows in stage two are in sternal
recumbency. They exhibit some degree of depression and partial paralysis. Animals in
the third stage are in lateral recumbency, completely paralyzed, typically bloated, and
severely depressed. They die within hours without treatment (Oetzel, 2013).
A second classification of hypocalcemia, the subclinical form, presents no clear
clinical signs, but affects approximately 50% of all multiparous cows and 25% of
primiparous cows (Reinhardt et al., 2011). Diagnosis is based on subnormal blood Ca
concentrations, and thresholds considered for diagnosis are usually between 2.00 and
2.13 mM (Reinhardt et al., 2011; Martinez et al., 2012). Cows with subclinical
54
hypocalcemia are more susceptible to other diseases like metritis and retained placenta
(Martinez et al., 2012).
Hypocalcemia is an economically important disease and can reduce the
productive life of a cow by 3.4 years (Payne, 1968). It has been estimated that the
average cost per clinical hypocalcemia case is $250 to $300, this value is based on the
direct cost of treatment and production losses (Horst et al., 1997; Kossaibati and
Esslemont, 1997). Furthermore, hypocalcemia also increase cows susceptibility to
retained placenta, metritis, and mastitis probably because of the impaired immune
competence (Kimura et al., 2006; Martinez et al., 2014). Cows that develop
hypocalcemia are more likely to have displaced abomasum, uterine prolapse, and
dystocia (Curtis et al., 1984) probably because of the reduced muscle contractility
induced by abnormally low blood ionized calcium. Finally, hypocalcemia increases the
risk of premature culling from the herd (Wilhelm et al., 1999). Because subclinical
hypocalcemia is prevalent and serves as a gateway disease for other periparturient
problems, it becomes a costly metabolic disease in dairy cows.
One of the areas of continuing contention is the role of pre-calving calcium intake
as a risk factor for milk fever (DeGaris and Lean, 2008). Early studies (Boda and Cole,
1956) found that feeding diets low in calcium reduced the risk of milk fever. It was later
supported in a qualitative literature review and suggested limiting prepartum calcium
intake to between 20 and 60 g/d (Thilsing-Hansen et al., 2002; Lean et al., 2006). The
NRC (2001) recommends diets with less than 15 g of calcium a day for at least 10 days
before calving as a method to prevent hypocalcemia. This strategy has the sole purpose
of placing the cow in a negative calcium balance, stimulating the PTH secretion before
55
calving. Green et al. (1981) showed the direct relation between feeding low calcium
diets prepartum and the increased plasma concentrations of 1,25-dihydroxyvitamin D
and hydroxyproline, factors closely related to PTH action in the body.
Oral administration of large amounts of calcium salts to force calcium absorption
by passive diffusion can also be used to increase blood calcium concentration during
the periparturient period. Martinez et al. (2016) dosed one single dose of 0, 43, or 86 g
of calcium the day of calving and showed that the postpartum ionized calcium
concentration in blood increased with dose, but concentrations remained elevated for
only 2 and 6 h in cows dosed with 43 and 86 g, respectively.
Another technique used to prevent hypocalcemia is to deliver more vitamin D and
vitamin D metabolites prepartum to increase calcium absorption from the gut.
Nevertheless, this technique can have side effects because active forms of injectable
vitamin D might impair endogenous synthesis of vitamin D and result in delayed
hypocalcemia (Horst et al., 1997). On the other hand, a single injection of 300 µg of
calcitriol within the first 6 hours after calving increased the concentrations of calcitriol
and calcium in plasma, and therefore, reduced the prevalence of subclinical
hypocalcemia approximately 50% in the first 3 d after calving (Vieira-Neto et al., 2017b).
One of the most significant and yet not completely understood methods to control
milk fever is the feeding of inorganic salts to cows prepartum (Ender et al., 1971; Block,
1984). It was speculated that the incidence of milk fever depended on the abundance of
strong cations (sodium and potassium) relative to strong anions (chloride and sulfur).
This concept is now generally referred to as the dietary cation-anion difference (DCAD)
(Ender et al., 1971). Research suggests that DCAD of -50 to -100 mEq/kg of dietary DM
56
is adequate for the prevention of milk fever (Horst et al., 1997; Moore et al., 2000;
Weich et al., 2013).
Goff et al. (1991) found that diets high in cations (+978 mEq/kg of DM)
decreased the ability of bone and renal tissues to respond to PTH, and that adding
anions to the diets increased tissue response to PTH and enabled the cow to better
adapt to the calcium demands of lactation. Abu Damir et al. (1994) found an increased
plasma concentration of 1,25-dihydroxyvitamin D, and an evident increase in cortical
bone remodeling in cows fed a negative cation-anion balance when compared with
cows fed a diet with positive DCAD (+779 vs. -35 mEq/kg of DM). The results of several
experiments support the hypothesis that a mild metabolic acidosis improves PTH tissue
responsiveness and consequently calcium metabolism (Goff et al., 2014).
Acidogenic Diets
Acidogenic diets are diets that have a higher concentratoion of anions than
cations and are designed to cause a compensated acidosis, that is an acidity that
homeostatic mechanisms can buffer so that a normal blood pH is maintained (Pehrson
et al., 1999).
Ender et al. (1971) using data from several experiments conducted in Norway
discovered that by replacing beets with large amounts of grass silage treated with
hydrochloric and sulfuric acid (used for long-term preservation of the silage), reduced
the episodes of milk fever and elevated calcium concentration in plasma after calving
from 5.0 to 7.4 mg/dL. These findings went largely unnoticed because the mechanism
of action was not understood and because they were made during a period when new
and very active vitamin D metabolites were being discovered (Horst et al., 1997). The
57
concept of feeding more anions (Cl and S) and the resulting effects on blood calcium
was brought back and revived by Block (1984). This led to the practice of feeding diets
with more anions relative to cations to help reduce the incidence of milk fever.
There are several possibilities to explain how negative DCAD helps to maintain
blood calcium. The two major ways to get more calcium into the blood are via increased
intestinal absorption and bone resorption (Favus and Goltzman, 2013). It is
demonstrated that manipulating DCAD affect intestinal absorption of calcium. Wilkens et
al. (2016) fed acidogenic diets to sheep and induced a compensated metabolic
acidosis. The decrease in blood pH increased tissue permeability and calcium flux rates
from the mucosal to the serosal side of the rumen epithelium. Another effect of chronic
acidosis is to increase tissue responsiveness to PTH as shown by Goff et al., (2014),
that adding acidogenic salts to the diets increased plasma hydroxyproline, calcium
concentration in blood around parturition, and the amount of 1,25-dihydroxyvitamin D
produced per increase in PTH. Since PTH regulates both bone calcium resorption and
renal 1,25-dihydroxyvitamin D production, we can conclude that acidogenic diets
increase PTH responsiveness.
The effects of reducing DCAD pre-partum on DM intake are equivocal. Some
researchers report a decline in DM intake when feeding negative DCAD diets (Horst et
al., 1994; Razzaghi et al., 2012; Martins et al., 2015) but others reported no difference
in dry matter intake when negative DCAD diets were fed before parturition (Oetzel et al.,
1991; Moore et al., 2000). This was settled in a meta-analysis performed by
Charbonneau et al. (2006) who showed a negative relationship between DCAD and pre-
partum DM intake. The authors showed a decrease of 1.3 kg of DM intake/d by
58
reducing the DCAD in 300 mEq/kg of diet DM when using the formula: DCAD = [(mEq
of Na + mEq K) – (mEq Cl + 0.6 mEq S)]. It was uncertain if the decrease in DM intake
is due to the palatability of the acidogenic products or if it is a consequence of the
negative acid-base status of the cow. Oetzel et al. (1991) tested the palatability of six
different acidogenic salts. There was no difference in intake between the salts, or when
compared to a control diet without the salts. Even though the acidogenic salts were fed
for a short period of time, there was a mild decrease in urine pH and acid excretion in
urine that suggested a mild acidosis. From these data then it can be hypothesized that
the reduction in dry matter intake might be more related to the extent of the acidosis,
than to the palatability of the salts. Recently, an experiment by our group (Zimpel et al.,
2018) confirmed this hypothesis by feeding 5 different diets in a duplicated 5 x 5 Latin
square design. Diets differed in level of DCAD, addition of acidogenic salts and addition
of Cl salts. They demonstrated that depression in intake was not related to the inclusion
of acidogenic salts (palatability), but by the effect of metabolic acidosis, because
incorporation of alkalogenic salts to buffer the acidogenic diet prevented the decline in
DM intake. Although one cannot discard that some salts might influence intake by
palatability, the evidence suggests that induction of metabolic acidosis irrespective of
the source of strong anions will induce a depression in intake in prepartum cows.
The optimal pre-partum DCAD to promote postpartum health and performance
has not been determined. Although, there is a recommended target DCAD of -50 to -
150 mEq/kg of dietary DM to prevent milk fever (NRC, 2001), it is unknown if this range
of DCAD is optimum for improvements of lactation performance and whether responses
differ among cow parity. It is thought that this range of DCAD provides a margin of
59
safety to account for varying mineral concentrations in feeds and potassium consumed
from forages (Block, 2010).
Diets with negative DCAD are to be fed in the pre-partum transition period
defined as the 21 days before calving because it is thought to maximize cow
performance and decreases postpartum disease (Pehrson et al., 1999; DeGaris and
Lean, 2008), although little data are available on prevention of diseases other than
hypocalcemia and whether yields of milk and milk components are influenced by length
of feeding negative DCAD. Some experiments have demonstrated that feeding
acidogenic diets might improve lactation performance of dairy cows (Weich et al., 2013),
and that extending the duration of feeding longer than 21 d might not be detrimental to
cow performance (Weich et al., 2013; Wu et al., 2014).
Urinary pH and DCAD are directly and positively related (Charbonneau et al.,
2006). Therefore, a common practice to monitor acidogenic diets is to routinely monitor
urine pH (Spanghero, 2004). It is also important to monitor the urine pH because
extremely low pH (< 5.5) could mean that there is an excess of acidogenic product
consumed by cows inducing a less compensated metabolic acidosis, which might have
negative consequences on energy metabolism (Bigner et al., 1996; Horst et al., 1997).
Suggested ranges of urine pH for prevention of hypocalcemia are between 5.5 and 6.5
(Jardon, 1995; Moore et al., 2000).
Acid-Base Balance
The acid-base balance or neutrality regulation maintains a pH around 7.4 in the
extracellular fluid by excreting carbon dioxide in the lungs and noncarbonic acid or base
60
in the kidneys. The result is a normal acid-base status in blood and extracellular fluid
(Siggaard-Andersen, 2006).
Acid-base abnormalities occur commonly in ruminants. The Henderson-
Hasselbalch equation and two physicochemical approaches, the strong ion model
(Stewart, 1983) and the simplified strong ion model, have been used to describe acid-
base balance in animals (Constable, 1999). The basic concept is the difference in
concentrations of strong cations, sodium and potassium, and strong anions, chloride
and sulfur, in blood. The term strong ion refers to the highly dissociated non-
metabolizable ions (Riond, 2001)
The Henderson-Hasselbalch equation has been invaluable in aiding our
understanding of acid-base physiology and is routinely used in the clinical management
of acid-base disorders in ruminants (Constable, 1999). It focuses on how plasma pH is
determined by the interaction between carbon dioxide tension, the bicarbonate
concentration, the negative logarithm of the apparent dissociation constant for carbonic
acid, and the solubility coefficient for carbon dioxide in plasma (Constable, 2014).
Strong ions enter the blood from the digestive tract, making the strong ion
difference of the diet the ultimate determinant of the blood strong ion difference. Once
absorbed, the concentration of strong ions in the blood is regulated by the kidneys
(Remer, 2000). Adjustment of the strong ion difference of the blood is slower than the
respiratory control of blood pH but is capable of inducing much greater changes in blood
pH (Oh, 2000). The difference between the number of cations and anions absorbed
from the diet determines the pH of the blood. For example, Hu and Murphy (2004) found
that feeding a positive DCAD diet to lactating cows increased the pH in blood. On the
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other hand, Pehrson et al. (1999) found that by feeding negative DCAD diets to dry
cows decreased blood pH by the second week of feeding from 7.485 to 7.451, this
change might seem insignificant, but blood pH is strongly regulated by the body.
Therefore, when diets with negative DCAD are fed to prepartum cows, the cows
undergo a compensated metabolic acidosis, and the excess acids are disposed through
the kidneys into the urine (Siggaard-Andersen, 2006). Wang and Beede (1992) showed
that feeding ammonium chloride and ammonium sulfate salts as acidogenic
supplements to Jersey cows reduced blood and urine pH. These reduction in pH,
increased urinary concentrations of titratable acid, ammonium, and net acid
concentration which reflect a compensatory response by the kidneys.
Strong linear associations between urinary net acid excretion, net plasma
bicarbonate concentration, and base excess have been shown (Grünberg et al., 2011;
Vagnoni and Oetzel, 1998). In other words, increase in urinary excretion of net acid
reflect regulations in acid-base homeostasis (Grünberg et al., 2011) coordinated by the
exchange of free hydrogen ions with carbon dioxide and an increase of respiration rate
to buffer the blood with the resulting bicarbonate (Siggaard-Andersen, 2006). The
metabolic acidosis is compensated by the animal in part through respiration, by
increasing output of CO2, so the metabolic acidosis does not affect the blood pH.
Therefore, when respiratory and renal compensations are able to excrete the excess of
protons, the metabolic acidosis does not represent an imminent danger to the animal
(Vagnoni and Oetzel, 1998; Constable, 1999; Grünberg et al., 2011).
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CHAPTER 3 EFFECTS OF LEVEL OF DIETARY CATION-ANION DIFFERENCE AND DURATION
OF PREPARTUM FEEDING ON PERFORMANCE AND METABOLISM OF DAIRY COWS.
Summary
The objective of the experiment was to evaluate the effects of feeding diets with
two negative dietary cation-anion differences (DCAD) during the last 42 or 21 days (d)
of gestation on performance and metabolism in dairy cows. The hypothesis was that
extending the duration of feeding from 21 to 42 d and reducing the DCAD from -70 to -
180 mEq/kg would not be detrimental to postpartum performance of dairy cows.
Holstein cows at 230 d of gestation were blocked by parity prepartum (48 primiparous
and 66 multiparous cows) and 305-d milk yield, and randomly assigned to one of 4
treatments arranged as a 2 x 2 factorial, with two levels of DCAD, -70 or -180 mEq/kg,
and two feeding durations, the last 21 d (Short) or the last 42 d (Long) prepartum
resulting in 4 treatments, Short -70 (n = 29), Short -180 (n = 29), Long -70 (n = 28) and
Long -180 (n = 28). Cows in the Short treatments were fed a positive DCAD diet (+110
mEq/kg of dry matter) from -42 to -22 d relative to calving. After calving, cows were fed
the same lactation diet and lactation performance and incidence of diseases were
evaluated for the first 42 d in milk (DIM), whereas reproduction and survival was
evaluated for the first 305 d postpartum. Blood was sampled pre- and postpartum for
quantification of metabolites and minerals. Lowering the DCAD reduced prepartum dry
matter (DM) intake by 1.0 kg/d in the first 21 d of the dry period (Positive DCAD = 11.5 ±
0.3 kg/d vs. Negative DCAD = 10.5 ± 0.4 kg/d) and 1.1 kg/d in the last 21 d of the dry
period (-70 mEq/kg = 10.8 ± 0.5 kg/d vs. -180 mEq/kg = 9.7 ± 0.5 kg/d). Cows fed the
more negative DCAD had increased concentrations of ionized calcium (iCa) in blood on
63
the day of calving (-70 mEq/kg = 1.063 ± 0.021 mM vs. -180 mEq/kg = 1.128 ± 0.020
mM). Extending the duration of feeding the diets with negative DCAD from 21 to 42 d
reduced gestation length by 2 d (Short = 277.2 ± 4.6 d vs. Long = 275.3 ± 5.3 d), milk
yield by 2.5 kg/d (Short = 40.4 vs. Long = 37.9 ± 1.0 kg/d) and tended to increase days
open because of reduced pregnancy per artificial insemination after all inseminations
(Short = 35.0 vs. Long = 22.6%). Results from the experiment suggest that increasing
the duration of feeding negative DCAD from 21 to 42 d prepartum impaired milk yield
and reproduction of cows in the subsequent lactation, although yields of fat-corrected or
energy-corrected milk did not differ with treatments. On the other hand, reducing the
DCAD from -70 to -180 mEq/kg of DM induced a more exacerbated metabolic acidosis,
increased iCa concentrations prepartum and on the day of calving, and decreased
colostrum yield in the first milking, but with minor consequences to performance in the
subsequent lactation. These results support the concept that feeding acidogenic diets
should be restricted to 21 d and that there is no need to reduce the DCAD to -180
mEq/kg.
Introductory Remarks
A large proportion of dairy cows undergo a period of disruption in Ca
homeostasis with the onset of colostrogenesis and lactation. The large demands for Ca
for colostrum and milk synthesis induce a sudden drop in blood concentrations of
ionized (iCa) and total Ca (tCa), resulting in some cows developing clinical
hypocalcemia, also known as milk fever (DeGaris and Lean, 2008). Normal
concentrations of tCa in blood usually ranges between 2.2 and 2.7 mM, but the onset of
lactation results in sequestration of Ca in the mammary gland followed by loss with
colostrum secretion, which can represent 7 to 10 times the estimated amount of tCa
64
present in blood of a cow (Horst et al., 2005). The irreversible loss of tCa results in
reductions in blood tCa to values lesser than 2.2 mM (Reinhardt et al., 2011; Martinez et
al., 2012). The inability of the cow to reestablish concentrations of iCa and tCa in blood,
either because of inadequate intestinal absorption, bone resorption and/or urinary
reabsorption is responsible for the development hypocalcemia in the first days of
lactation. Reinhardt et al. (2011) used the cut-off values of serum concentrations of tCa
between 1.4 and 2.0 mM as indicating subclinical hypocalcemia and concentrations
below 1.4 in mM as clinical hypocalcemia. Using those cut-off values, the authors
reported prevalence of 1% of clinical hypocalcemia and 25% subclinical hypocalcemia
for primiparous cows, and 7% clinical hypocalcemia and 47% subclinical hypocalcemia
for multiparous cows in the first 48 h of calving. Cows that develop subclinical and
clinical hypocalcemia have impaired subsequent health and reproduction (Curtis et al.,
1985; Martinez et al., 2012).
Strategies have been developed to minimize the risk of sudden changes in blood
Ca concentrations in dairy cows. Ender et al. (1971) demonstrated that feeding
prepartum diets richer in strong anions relative to strong cations increased blood
concentrations of Ca and prevented clinical hypocalcemia, also called milk fever, in
dairy cows. These findings eventually led to the practice of feeding acidogenic diets to
decrease hypocalcemia on dairy farms, and introduced the concept of dietary cation-
anion difference (DCAD) for formulation of diets for prepartum dairy cows. One of the
effects of acidogenic diets is a reduction in dry matter intake prepartum (Charbonneau
et al., 2006; Martinez et al., 2018a), and the decline seems to follow a linear relationship
with the decrease in DCAD (Charbonneau et al., 2006). Although numerous
65
experiments have documented the benefits of acidogenic diets prepartum (Block, 1984),
the ideal DCAD to optimize postpartum health and performance remain unclear.
Excessive feeding of acidogenic diets might influence energy metabolism and impair
insulin sensitivity (Bigner et al., 1996). Despite the calculated DCAD fed, acidogenic
diets will vary in DCAD in part because of the variability in mineral composition in major
feedstuffs, specially forages (St-Pierre and Weiss, 2017), which seems to be a common
finding in dairy herds (Stone and Mosley, 2017).
Under some feeding management systems, providing a single diet prepartum
might facilitate implementation of acidogenic diets. It has been suggested that grouping
cohorts of dry cows with similar calving dates in the same pen to minimize pen
movements and regrouping (Weich et al., 2013) creates convenience and might provide
advantages in reducing social disturbance and better adaptation to the postpartum diets
(Goff and Horst, 1997). Nevertheless, only two experiments have evaluated the impacts
of feeding acidogenic diets prepartum longer than the traditional 21 d (Weich et al.,
2013; Wu et al., 2014). In those experiments, cows were fed diets with -150 mEq/kg
(Weich et al., 2013) or -200 mEq/kg (Wu et al., 2014) and no detrimental impacts were
observed in postpartum performance when feeding was extended from 21 to 42 d
prepartum.
Most experiments have focused on the effects that feeding different levels of
DCAD on the performance and metabolism of the cow, but limited research has been
conducted on the effects of a prolonged duration of feeding the diets with negative
DCAD to transition cows. Based on the limited data available, we hypothesized that
decreasing the negative DCAD from -70 to -180 mEq/kg and extending the duration of
66
feeding from 21 to 42 d will not affect performance and metabolism in dairy cows.
Therefore, the objectives of this experiment were to evaluate the effects of two
durations of feeding acidogenic diets prepartum, the last 21 or 42 d of gestation, and at
two levels of negative DCAD, -70 or -180 mEq/kg, on acid-base status, colostrum yield
and composition, lactation performance, health, and reproduction in Holstein dairy
cows.
Materials and Methods
The University of Florida Institutional Animal Care and Use Committee approved
all procedures involving cows in the experiment under the protocol number 201509133.
Cows and Housing
The experiment was conducted in the University of Florida Dairy Unit from
November 2015 to July of 2016. One-hundred and fourteen dry Holstein cows, 48 cows
that completed the first lactation and 66 cows completing lactation 2 or greater.
Selection criteria included only apparently healthy cows. Details of cows enrolled in the
experiment according to treatment is presented in Table 3-1.
Pregnant, nonlactating cows at 230 ± 3 d of gestation were moved to the
experimental free-stall barn to acclimate to the facilities and to the individual feeding
gates (Calan Broadbent feeding system, American Calan Inc., Northwood, NH). Cows
were trained to use individual feeding gates and the first 2 d of feed intake were not
considered for statistical analysis. Therefore, measurements started at 232 ± 3 d of
gestation and measurements during the last 42 d of gestation were used for statistical
analysis of data prepartum.
All prepartum cows were housed together in a free-stall barn with sand bedded
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stalls and each cow was randomly assigned to an individual feeding gate. Immediately
after calving, all postpartum cows were moved to a second pen and housed together
where they remained for the first 42 DIM. The experimental pens were equipped with
two rows of fans (1 fan/6 linear meters) placed above the beds and a water soaker line
with nozzles was placed above the feedbunk for cooling of cows. Fans and water
spraying were controlled by thermostats and activated when ambient temperature
reached 18oC.
Feeding Management and Treatments
Prepartum cows were fed once daily at 0730 h and thrice daily postpartum at
approximately 0700 h, 1100 h, and 1500 h. Individual feed intake was measured daily
only during the prepartum period. Postpartum cows were fed as a group. The amounts
of feed offered to individual cows prepartum were adjusted daily to result in at least 5%
refusals, which were weighed once daily, before the morning feeding. The amount
offered to postpartum cows was adjusted daily to assure at least 5% refusals.
The experiment followed a randomized complete block design with cow as the
experimental unit. Weekly cohorts of prepartum cows at 230 d of gestation were
blocked by parity (1 vs. > 1) and previous lactation 305 d milk yield and, within each
block, assigned randomly to one of the four treatments. Treatments were arranged as a
factorial with two levels of negative DCAD, -70 mEq/kg of DM (-70) or -180 mEq/kg of
DM (-180) fed for two durations, the last 21 d of gestation, designated as the short
period of feeding, or the last 42 d of gestation, designated as the long period of feeding.
Therefore, the four treatments were Short -70, Short -180, Long -70, and Long -180.
For cows in treatments Short, a diet with a positive DCAD of +110 mEq/kg of DM was
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fed from 230 to 255 d of gestation. Cows assigned to the Short -70 and Short -180
treatments were switched to the respective negative DCAD diets, -70 and -180 mEq/kg,
at 256 d of gestation and fed those diets until calving. Prepartum diets were formulated
to be isocaloric, isonitrogenous, and have the same forage content and mineral
composition, except for concentrations of strong ions to manipulate the DCAD to
achieve -70 or -180 mEq/kg of DM. Description of diets is presented in Table 3-2.
Ingredient Sampling, Chemical Analyses, and Calculation of DM Intake
Forages and concentrate mixtures were collected weekly, dried at 55oC for 48 h and
moisture loss recorded, and stored for later analyses as monthly composites. Dried
samples were ground to pass a 1 mm screen of a Wiley mill (Thomas Scientific,
Swedesboro, NJ), and analyzed for DM (105°C for 12 h). Dried samples were
composited monthly and then analyzed for organic matter (512°C for 8 h), sequential
analysis of neutral detergent fiber using a heat stable α-amylase and acid detergent
fiber (Van Soest et al., 1991), nitrogen using an automated quantitative combustion
digestion method (LECO FP628, LECO Corp. St. Joseph, MI), starch after acid
hydrolysis (Vidal et al., 2009), total fatty acids (Sukhija and Palmquist, 1988), and
minerals by inductively-coupled plasma mass spectrometry. The net energy density of
the diets was calculated using chemical analyses of dietary ingredients and calculated
for 12.0 and 18.0 kg of DM intake for the pre- and postpartum periods, respectively,
using the NRC (2001) model (Table 3-2). Prepartum intake of DM for each cow was
calculated daily for the last 42 d of gestation based on the weekly DM content measured
at 105 oC of the ingredients and the respective composition of diets.
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Body Weight and Body Condition Score
Cows were weighed on the day of experiment enrollment and then once weekly
prepartum, in the morning, until calving. Body condition was scored on the day of
enrollment and then once weekly by the same trained evaluator using a 1 to 5 scale
(Ferguson et al., 1994) with increments of 0.25 units as depicted in the Elanco body
condition score (BCS) chart (Elanco, 2009). During the postpartum period, immediately
after each milking, cows were weighed on a walk-though scale (AfiWeigh, S.A.E. Afikim,
Israel) located on the exit lane of the milking parlor. Body condition was scored once
weekly as described previously.
Blood Sampling and Processing
Starting at 256 d of gestation, blood was sampled from all cows every other day
until calving, and then on d 0, 1, 2, 3, 4, 5, 7, 14 and 21 postpartum by puncture of the
coccygeal blood vessels into evacuated tubes (Vacutainer, Becton Dickinson, Franklin
Lakes, NJ). Tubes contained either lithium heparin as an anticoagulant agent for plasma
separation and subsequent analyses of tCa, total P (tP), total Mg (tMg), and glucose, or
K2 ethylenediaminetetraacetic acid as an anticoagulant for plasma separation and
analyses of nonesterified fatty acids (NEFA) and beta-hydroxybutyric acid (BHB).
Immediately upon sampling, tubes were placed in ice and transported to the laboratory
within 1 h. Cold tubes were centrifuged for 15 min at 2,500 x g at room temperature for
plasma separation. Plasma samples were transferred into multiple aliquots of 1.0 or 2.0
mL and stored frozen at -20°C until analyses.
For the prepartum period, samples collected on d -14, -12, -10, -8, -6, -4, and -2
relative to calving were assayed for concentrations of tCa, tP, tMg, glucose, NEFA, and
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BHB. Postpartum samples collected on d 0, 1, 2, 3, 4, 5, 7, 14, and 21 were assayed for
concentrations of glucose, NEFA and BHB, whereas those collected on d 0, 1, 2, 3, 4,
5, and 7 were assayed for concentrations of tCa, tP, and tMg.
Sampling Whole Blood and Measurements of Ionized Ca, Na, K, and Measures of
Acid-Base Status
Whole blood was sampled by puncture of the jugular vein from all cows at 255 d
of gestation, the day before cows assigned to the Short treatments were switched to
their respective negative DCAD diets. Whole blood was sampled again from a subset of
the first 21 blocks comprising 80 cows (Short -70 = 21, Short -180 = 20, Long -70 = 19,
and Long -180 = 21) at 268 and 272 d of gestation, corresponding to -10 and -6 d
relative to expected calving, and at 0, 1, 2, 3, and 4 d postpartum. Samples were
analyzed within 1 to 2 min for concentrations of iCa, Na, K, pH, bicarbonate, base
excess, total dissolved CO2 (tCO2), saturation of O2 (sO2), and partial pressures of O2
(pO2) and CO2 (pCO2) using a handheld biochemical analyzer (VetScan i-STAT,
Abaxis, Union City, CA).
Blood Assays
All assays followed the initial randomization with blocks such that samples from
each block were analyzed in the same assay. Plasma concentrations of NEFA (NEFA-C
kit; Wako Diagnostics Inc., Richmond, VA; according to Johnson and Peters, 1993) and
BHB (Wako Autokit 3-HB; Wako Diagnostics, Inc., Richmond, VA) were analyzed using
colorimetric enzymatic assays. The intra- and inter-assay coefficient of variation (CV)
were, respectively, 3.4 and 8.4% for NEFA, and 1.0 and 4.0% for BHB. Concentrations
71
of glucose in plasma were determined by colorimetric continuous flow analysis
(Autoanalyzer II, SEAL Analytical, UK) using a modification of the method described by
Gochman and Schmitz (1972). Plasma concentrations of tCa and tMg were analyzed by
atomic absorption sing a spectrophotometer equipped with Ca and Mg specific hollow
cathode lamps (AAnalyst 200, Perkin-Elmer Inc., Waltham, MA) as described by
Martinez et al. (2012). Intra- and inter-assay CV were, respectively, 1.8 and 5.1% for
tCa and 1.6 and 4.4% for tMg. Concentrations of tP were quantified in plasma using the
molybdenum blue method (Quinlan and DeSesa, 1955). The intra- and inter-assay CV
were, respectively, 3.4 and 10.1%.
Urine Collection and Analysis
Urine samples were collected twice weekly prepartum, on Wednesdays and
Saturdays, by manually stimulating the perineal area until a clean and copious stream of
urine was obtained. Samples were collected into 50 mL plastic tubes that were placed in
ice and pH measured within 10 minutes of collection using a pH meter (Accumet AR15
pH meter, Fisher Scientific International, Inc. Hampton, NH). Samples collected in the
last 2 weeks of gestation were composited by week and each composite sample split
into multiple aliquots and stored at -20°C until analyses. Concentrations of tCa, tMg,
and creatinine were analyzed in duplicates for each sample using the colorimetric
methods in a biochemical analyzer (kits no. CA3871, MG3880, and CR3814, Randox
Laboratories Ltd, UK). The intra- and inter-assay CV were, respectively, 3.2 and 1.4%
for tCa, 2.5 and 4.5% for tMg, and 3.3 and 5.8% for creatinine. All assays followed the
initial randomization with blocks such that samples from each block were analyzed in
the same assay. Creatinine was used as a marker to estimate daily urinary volume
72
based on the constant excretion of 29 mg of creatinine per kg of body weight (BW) per
day as follows: Urinary volume = BW x 29 / creatinine concentration (mg/L) (Valadares
et al., 1999). The estimate of daily urinary volume was calculated using the mean BW of
each cow in the week the urine sample was taken. Daily urinary excretions of tCa and
tMg were calculated as the product of urinary volume and the respective concentrations
of those minerals in the urine samples.
Measurement and Analysis of Colostrum
Cows were milked within the first 6 h after calving and colostrum yield was
measured and recorded for the first and second milkings (AfiFlo; S.A.E. Afikim, Israel).
Duplicate samples were collected during the first and second milkings and diluted 1 to 1
with skim milk. Samples of skim milk and diluted colostrum samples were analyzed in
duplicates for concentrations of fat, true protein, lactose, solids-not fat, total solids, urea
N, and somatic cell count (SCC) at the Dairy Herd Improvement Southeast Milk
laboratory (Belleview, FL). Concentrations in the original colostrum samples were
calculated based on the concentrations of each component in skim milk and in the
diluted samples and the 1 to 1 dilution factor.
A sample of colostrum from first milking postpartum was frozen for subsequent
analysis of concentration of immunoglobulin (Ig) G by radial immunodiffusion assay
(Triple J Farms, Bellingham, WA) per manufacturer’s protocol. Briefly, colostrum was
diluted 1 to 5 in 0.9% saline such that the concentration of IgG would fall within the
linear range of the standard curve of the assay. The diluted samples were pipetted in
duplicates into the bovine anti-bovine IgG antibody plate, and incubated for 27 h in a flat
surface protected from light. The diameter of the precipitin ring was measured using a
73
7x scale loupe (n ͦ. 1975, Peak Optics, Japan) and used to calculate the IgG
concentrations. The intra- and inter-assay CV were, respectively, 1.8 and 2.3%.
Measurements of Yields of Milk and Milk Components
Cows were milked twice daily at 0600 h and 1800 h, and yields of milk were
recorded automatically (AfiFlo milk meters, S.A.E. Afikim, Israel) for the first 42 DIM.
Samples of milk were collected two days a week, on Mondays and Wednesdays, from
two sequential milkings, morning and afternoon, for measurements of concentrations of
fat, true protein, lactose, and SCC at the DHI Southeast Milk laboratory (Belleview, FL).
Milk yield from each sampling was used to calculate the final concentrations of milk
components. Yields of milk corrected for 3.5% fat content and for energy, and the net
energy (NE) content of milk were calculated as: 3.5% FCM kg/d = 0.4324 x milk kg +
(16.218 x milk fat kg); energy corrected milk (ECM) kg/d = [(0.3246 x Milk yield) +
(12.86 x fat yield) + (7.04 x protein yield)]; NE Mcal/kg = (0.0929 x fat %) + (0.0563 x
protein %) + (0.0395 x lactose %).
Measurement of Net Energy Balance Prepartum
Energy balance was calculated using daily caloric intake from DM intake and the
energy content of the diets according to NRC (2001) using the NE system. The needs
for maintenance were calculated based on the formula of NRC (2001) and according to
metabolic BW (0.08 x BW0.75). Calories required for gestation for prepartum cows were
calculated at 3.7 Mcal of NE/d for a calf that would eventually be born weighing 43 kg
(NRC, 2001). Net energy intake was calculated based on the NE content of the diets
using the NRC (2001) and each cow’s DM intake.
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Characterization and Diagnosis of Health Problems
Milk fever was characterized by a down cow that responded to intravenous
administration of a solution containing 10.8 g of Ca as Ca borogluconate (Cal-Dex
CMPK injection, Agrilabs, St. Joseph, MO). A blood sample was collected immediately
before intravenous treatment to confirm the diagnosis by measuring the concentration of
iCa. Retained placenta was characterized by the retention of fetal membranes the day
after calving. Metritis was evaluated by transrectal palpation on d 4, 7 and 12
postpartum and characterized by an enlarged uterus with fetid watery discharge. All
cows had rectal temperature measured on d 4, 7, and 12 postpartum, and those with
temperatures greater than 39.5°C were classified as having fever. Cows with fever
concurrent with metritis were classified as having puerperal metritis. At every milking, all
cows were examined for signs of clinical mastitis by the herd personnel immediately
before milking. Mastitis was characterized by the presence of abnormal milk in one or
more quarters. Displaced abomasum was diagnosed by percussion and auscultation of
the flanks and confirmed by during surgical intervention for correction by omentopexy.
Cows with more than one clinical disease event were classified as having multiple
diseases. Morbidity included any of the above clinical diseases: milk fever, retained
placenta, metritis, mastitis, and displaced abomasum. Disease information was
recorded from the day of parturition to 42 d in milk. Removal from the herd was
determined for the first 305 DIM.
Subclinical hypocalcemia was analyzed considering three distinct thresholds, whole
blood iCa ≤ 1.0 mM (Oetzel et al., 1988), plasma tCa ≤ 2.0 mM (Reinhardt et al., 2011),
or plasma tCa < 2.15 mM (Martinez et al., 2012). Incidence of subclinical hypocalcemia
75
was based on at least one sample with concentration below the respective threshold on
d 0, 1, 2, 3, or 4 postpartum. Daily prevalence was calculated using the same
thresholds from 0 to 4 d postpartum.
Reproductive Management and Reproductive Responses
All cows were subjected to the double Ovsynch protocol for first artificial
insemination (AI) (Souza et al., 2008). Briefly, cows received an i.m. injection of 100 μg
of GnRH (Cystorelin, 50 μg/mL gonadorelin diacetate tetrahydrate, Merial, Duluth, GA)
at 53 ± 3 DIM, followed by an injection of 25 mg of PGF2α (Lutalyse Sterile Solution, 5
mg/mL dinoprost as tromethamine salt; Zoetis, Florham Park, NJ) at 60 ± 3 DIM, and
another injection of 100 μg of GnRH at 63 ± 3 DIM. Seven days later, at 70 ± 3 DIM, the
same sequence of injections was repeated with the final GnRH administered in the
afternoon of 79 ± 3 postpartum, and timed AI performed in the morning of day 80
postpartum, approximately 14 to 16 h after the final GnRH treatment. Pregnancy was
diagnosed on d 32 after each AI based on the presence of an amniotic vesicle with an
embryo with heartbeat by transrectal ultrasonography. Nonpregnant cows had the
estrous cycle resynchronized for timed AI with the Ovsynch protocol to be re-
inseminated 10 d after the nonpregnancy diagnosis.
Pregnant cows on d 32 were re-evaluated for pregnancy 35 d later, at 67 d after
AI. For statistical analyses, the diagnosis on d 67 after AI was used to determine if a
cow became pregnant to the first or subsequent AI. Interval to pregnancy up to 305 d
postpartum was recorded. Cows that became “do not inseminate”, were sold or died, or
remained nonpregnant by 305 d postpartum were censored.
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Responses measured included proportion of cows receiving AI, days postpartum
at first AI, pregnancy per AI at first AI, pregnancy per AI at all AI, and interval to
pregnancy.
Statistical Analysis
The experiment followed a randomized complete block design with a 2 x 2
factorial arrangement of treatments with 2 durations of feeding (21 vs. 42 d) and 2 levels
of negative DCAD (-70 vs. -180 mEq/kg of DM) and cow as the experimental unit.
Prepartum cows at 230 ± 3 d of gestation were blocked by parity (lactation 1 vs.
lactation > 1) and previous lactation 305-d milk yield and, within each block, assigned
randomly to one of the four treatments.
Normality of residuals and homogeneity of variance were examined for each
continuous dependent variable analyzed after fitting the final model. Responses that
violated the assumptions of normality were subjected to power transformation according
to the Box-Cox procedure (Box and Cox, 1964) using PROC TRANSREG in SAS (SAS
ver. 9.4, SAS/STAT, SAS Institute Inc., Cary, NC). The variables transformed were
prepartum blood BHB transformed to the inverse, and postpartum blood NEFA, BHB
and glucose transformed to the logarithm. The least squares mean (LSM) and standard
error of the mean (SEM) were back transformed for presentation according to
Jørgensen and Pedersen (1998).
During the prepartum period, two statistical models were built, one for d -42 to -
22 relative to calving and another for d -21 to -1 relative to calving. The reason was that
from 232 to 255 d of gestation, cows assigned to the Long treatments were fed a diet
with +110 mEq/kg based on the design of the experiment.
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Data for the first 21 d of the dry period, were analyzed by ANOVA with the
MIXED procedure of SAS (SAS/STAT). The statistical models included the fixed effects
of level of DCAD (+110 vs. -70 vs. -180 mEq/kg), day of measurement, the interaction
between treatment and day, parity group, and calf gender (female vs. male vs. twin),
and the random effects of block, and cow nested within treatment. Data with a single
measurement per cow was analyzed with the fixed effects of treatment, parity group,
and calf gender, and the random effect of block. Orthogonal polynomial contrasts were
used to determine linear and quadratic effects of DCAD. For the last 21 d of gestation,
from d -21 to -1 relative to calving, data were analyzed by ANOVA with the MIXED
procedure of SAS (SAS/STAT). The statistical models included the fixed effects of
duration of feeding, level of DCAD, day of measurement, parity group, calf gender
(female vs. male vs. twin), the interactions between duration and DCAD, duration and
day, DCAD and day, and duration and DCAD and day, and the random effects of block
and cow nested within duration and DCAD.
Postpartum data were analyzed separately from prepartum data. Continuous
variables were analyzed by ANOVA with the MIXED procedure of SAS (SAS/STAT).
The statistical models included the fixed effects of duration of feeding, level of DCAD,
day of measurement, parity group, calf gender (female vs. male vs. twin), the
interactions between duration and DCAD, duration and day, DCAD and day, and
duration and DCAD and day, and the random effects of block and cow nested within
duration and DCAD. For yields of milk and milk components, the previous lactation yield
was used as covariate in the statistical models. Colostrum composition and changes in
BW and BCS were analyzed with models that included the fixed effects of duration of
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feeding, level of DCAD, parity group, calf gender, and the interactions between duration
and DCAD, and the random effect of block.
For all mixed models with continousou data, the Kenward-Roger method was
used to approximate the denominator degrees of freedom for the F tests in the
statistical models. Model fit was assessed based on the smallest corrected Akaike’s
information criterion. For repeated measures, the covariance structure was selected for
each model based on spacing of measurements and the smallest corrected Akaike’s
information criterion. When an interaction was significant, pairwise comparisons were
performed with the adjustment by Tukey.
Binary data were analyzed by logistic regression with the GLIMMIX procedure of
SAS (SAS/STAT). The statistical models included the fixed effects of duration of
feeding, level of DCAD, interaction between duration and DCAD, parity group, and calf
gender, and the random effect of block. Binary data with repeated measures within cow
such as daily prevalence of subclinical hypocalcemia and hyperketonemia, the
statistical models included the fixed effects of duration of feeding, level of DCAD, day,
parity group, calf gender, and interaction between duration and DCAD, duration and
day, DCAD and day, and duration and DCAD and day, and the random effects of block
and cow nested within duration and DCAD.
Time to an event such as pregnancy or leaving the herd was analyzed with the
Cox’s proportional hazard regression using the PHREG procedure of SAS (SAS/STAT).
The model included the fixed effects of duration of feeding, level of DCAD, interaction
between duration and DCAD, parity group, and calf gender. When the interaction
between duration and DCAD was nonsignificant (P > 0.10), it was dropped from the final
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model. The adjusted hazard ratio (HR) and the 95% CI were calcualted. The LIFETEST
procedure of SAS (SAS/STAT) was used to generate the survival curves and compute
the LSM ± SEM and median days to event.
Statistical significance was considered at P ≤ 0.05, and tendency was considered
at 0.05 < P ≤ 0.10.
Results
All 114 cows enrolled in the experiment were included in all statistical analyses,
unless the cow died before 42 d postpartum, in which case she contributed with data
until the day of death. One cow fed Long -180 developed obturator nerve paralysis after
calving and health data for this cow included only diagnosis of retained placenta and
milk fever. She was excluded from all other postpartum analyses. Number of days dry,
gestation length, and days prepartum on the experiment did not differ among treatments
(Table 3-1). Gestation length was 2 d shorter (P = 0.05, data not shown) for cows fed
the Long compared with the Short treatments, but no effect (P = 0.15) of DCAD or
interaction between duration and DCAD (P = 0.78) was detected. As designed, cows
fed the Short treatments received the diets with negative DCAD for approximately 21 d,
whereas those fed the Long treatments received the diets with negative DCAD for a
mean of 43 d (Table 3-1).
Intake, Measures of Energy Status, and Acid-Base Balance in the Early Dry Period
From d -42 to -22 relative to calving, cows enrolled in the Short treatments were
fed a diet with +110 mEq/kg and data were analyzed with 3 DCAD treatments.
Reducing the DCAD from +110 to -180 mEq/kg linearly reduced (P = 0.02) DM intake
which, consequently, had a linear effect in reducing (P = 0.01) caloric intake (Table 3-3).
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Because of less caloric intake, NE balance reduced linearly (P = 0.02) as the DCAD
become more negative. An interaction (P = 0.008) between treatment and day was
detected because the differences in DM intake increased with days in the experiment
(Figure 3-1A). The mean body weight and body condition score did not differ among
treatments.
Blood pH did not differ with treatment, although blood of cows showed typical
signs of a compensated metabolic acidosis as linear reductions in tCO2, pCO2,
bicarbonate, base excess, and urine pH were detected with decreasing DCAD (Table 3-
3). Urinary pH remained relatively constant according to treatment throughout the first
21 d in the experiment (Figure 3-1C). Concentrations of iCa, Na, K, and glucose did not
differ with treatment (Table 3-3).
Intake and Measures of Energy Status in the Late Dry Period
Duration of feeding did not affect DM intake in the last 21 d of gestation, but
reducing the DCAD from -70 to -180 mEq/kg reduced (P = 0.005) DM intake by 1.1 kg/d
(-70 = 10.8 vs. -180 = 9.7 ± 0.4 kg/d; Table 3-4), and the reduction was observed in
cows fed Short or Long throughout the 21-d period (Figure 3-1B). The reduction in DM
intake resulted in less (P = 0.007) caloric intake in cows fed -180 than -70 mEq/kg and
lower (P = 0.007) NE balance (Table 3-4). An interaction (P = 0.03) between duration of
feeding and DCAD was detected for body weight BW in part because cows fed Short -
180 were heavier than cows fed Long -180. Also, an interaction (P = 0.01) between
duration of feeding and DCAD was observed for body weight change because cows fed
Short -70 gained more weight than cows fed Short -180 or Long -70.
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The body condition of cows did not differ with treatment, but the change from
week -6 to -1 tended (P = 0.06) to differ with DCAD because cows fed -70 lost less body
condition than cows fed -180.
Acid-Base Balance and Urinary Excretion of Minerals Prepartum
In the last 21 d of gestation, reducing the DCAD from -70 to -180 reduced (P <
0.001) blood pH, tCO2, bicarbonate and base excess (Table 3-5). Duration of feeding
acidogenic diets did not influence blood measures of acid-base balance. A tendency (P
= 0.07) for interaction between duration and DCAD was observed for pCO2 because
feeding -180 reduced pCO2 only in cows fed Short.
Duration of feeding acidogenic diets prepartum did not influence urinary pH,
volume, concentrations of Ca or Mg, and excretions of Ca and Mg (Table 3-5). On the
other hand, reducing the DCAD from -70 to -180 decreased (P < 0.001) urinary pH, but
increased (P < 0.01) urinary volume and concentration and excretion of Ca in urine.
Concentration of Mg in urine tended (P = 0.07) to be greater for cows fed -70 than -180,
but urinary excretion did not differ with altering the level of DCAD. Once cows fed Short
were switched from a diet with +110 to either -70 or -180 mEq/kg, urinary pH declined
within 24 h (data not shown), and pH remained stable according to treatment in the last
21 d of gestation, although an interaction (P = 0.03) between duration and day was
observed because of the changes in the first days after diet switch (Figure 3-1D).
Concentrations of Minerals and Metabolites in Blood
Duration of feeding acidogenic diets prepartum did not affect concentrations of
minerals or metabolites in whole blood or plasma in the last 21 d of gestation (Table 3-
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6). Reducing the DCAD from -70 to -180 increased (P = 0.002) whole blood
concentrations of iCa in cows fed Short and Long (Figure 3-2A). Nevertheless, DCAD
did not affect concentrations of plasma tCa and tMg (Figure 3-2B and 3-2C), and whole
blood concentrations of Na and K. An interaction (P = 0.008) between duration and
DCAD was detected for plasma tP in part because within cows receiving the -70 diet,
those fed Long had greater (P < 0.05) concentrations than cows fed Short (Figure 3-
2D). Treatment did not affect concentrations of glucose and BHB in plasma prepartum;
however, an interaction (P = 0.05) between duration and DCAD affected the
concentration of NEFA in plasma, and cows fed Short -180 had greater (P < 0.05)
concentration than cows fed Long -180 (Table 3-6).
Colostrum Yield and Composition
Yield of first milking colostrum did not differ with duration of feeding, but it was
greater (P = 0.04) for cows fed the -70 than the -180 diet (Table 3-7). Treatment did not
affect concentrations of fat, lactose, total solids, NE, Ca, Mg, IgG, and somatic cell
score. Tendencies (P = 0.09) for duration were observed for concentrations of true
protein and solids not fat in first milking colostrum, although no statistical differences
were observed among treatments after Tukey-protected pairwise comparisons. Duration
of feeding did not affect yields of any of the milk components measured; however, cows
fed the -70 diet tended (P ≤ 0.09) to produce more true protein and solids not fat in
colostrum, and produced more (P = 0.03) lactose, and secreted more (P < 0.05) Ca and
Mg than cows fed the -180 diet.
Treatments had minor effects on second milking colostrum yield and composition
(Table 3-7). Neither duration of feeding nor level of DCAD affected concentrations of fat,
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true protein, lactose, solids not fat, totals solids, and NE in second milking colostrum.
The concentration of Ca increased (P = 0.01) in second milking colostrum of cows fed
Long than Short, whereas that of Mg increased (P = 0.05) only in cows fed Long -180
compared with Short -180. Yields of second milking colostrum and components in
second milking colostrum did not differ with treatment.
Lactation Performance
Increasing the duration of feeding acidogenic diets prepartum from 21 to 42 days
reduced (P = 0.03) milk yield by 2.5 kg/d (Short = 40.4 vs. Long = 37.9 ± 1.0 kg/d; Table
3-8; Figure 3-4A). Nevertheless, yields of 3.5% fat-corrected milk and energy-corrected
milk did not differ with treatment (Table 3-8; Figure 3-4B). Altering the level of DCAD did
not affect yields of milk, 3.5% fat-corrected milk, or energy-corrected milk. Treatment did
not influence concentrations and yields of fat and true protein in milk; however, the
reduced milk yield in cows fed Long than Short resulted in less (P = 0.04) yield of
lactose and a tendency (P = 0.06) for less yield of solids not fat for those cows. The
somatic cell score did not differ with treatment. As expected, cows lost body weight
(Figure 3-4C) and body condition (Figure 3-4D), but the mean body weight and body
condition score and the losses in the first 42 d postpartum did not differ due to duration
of feeding or level of DCAD prepartum (Table 3-8).
Acid-Base Balance Postpartum
Duration of prepartum feeding acidogenic diets did not influence any of the
measure of acid-base status in blood postpartum. Blood pH postpartum tended (P =
0.09) to be greater for cows fed -180 than those fed -70 DCAD prepartum (Table 3-9).
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On the other hand, feeding the -70 DCAD prepartum reduced (P < 0.05) tCO2,
bicarbonate, and base excess in blood, although the reduction in bicarbonate was only
evident in Long -70 cows.
Blood Concentrations of Minerals and Metabolites Postpartum
Concentrations of iCa, tCa, and tP sharply declined (P < 0.001) on the day of
calving, whereas those of tMg increased with the onset of lactation (Figure 3-2 A-D).
Treatments did not influence concentrations of iCa, tCa, tP, and Na in the first days
postpartum (Table 3-10), although an interaction (P = 0.04) between DCAD and day
postpartum was observed for iCa because cows fed the -180 DCAD had greater iCa
concentrations on the day of calving than those fed the -70 DCAD prepartum (Figure 3-
2A). Cows fed Long -70 and Long -180 had greater (P = 0.05) concentrations of tMg
than those fed Short -70 and Short -180. An interaction (P = 0.008) between duration
and DCAD affected blood K because cows fed Short -180 had a smaller (P < 0.05)
concentration of K than those fed Short -70 or Long -180.
Concentrations of glucose in plasma sharply increased (P < 0.001) on the day of
calving to 5.18 ± 0.22 mM, and then declined to approximately 2.95 ± 0.13 mM by 3 d
postpartum (Figure 3-3A). Increases in plasma NEFA and BHB concentrations with the
onset of lactation were also observed, but they were not as acute, and their
concentrations remained elevated until 21 d postpartum (Figure 3-3B and 3-3C). An
interaction (P = 0.05) between duration of feeding and DCAD affected mean plasma
glucose postpartum because concentrations were greater for cows fed Short -70 and
Long -180 than Short -180 and Long -70, although pairwise comparisons did not detect
differences among individual treatments (Table 3-10). An interaction (P = 0.04) between
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duration and DCAD also affected plasma BHB concentrations, but now because cows
fed Short -70 and Long -180 had less BHB than cows fed Short -180 and Long -70.
Similar to plasma glucose, pairwise comparisons did not detect differences among
individual treatments. Cows fed the acidogenic diets for the Short duration tended (P =
0.09) to have greater NEFA concentrations in plasma than those fed Long.
Health and Survival
Two cows were diagnosed with milk fever, one fed Short -70 and one fed Short -
180. One cow fed Short -70 developed milk fever approximately 12 h before calving and
the iCa concentration immediately before treatment with an intravenous solution
containing 10.8 g of Ca as Ca borogluconate was only 0.58 mM. Twenty-four hours
later, whole blood iCa was 1.16 mM. The second cow, fed Short -180, was diagnosed
with milk fever hours after milking colostrum and she also recovered after administration
of intravenous solution of Ca.
Treatment did not affect the incidence of retained placenta, metritis, puerperal
metritis, mastitis, or displaced abomasum (Table 3-11). In the first 42 DIM, morbidity
affected 32.7% of the experimental cows and 15.1% of them were diagnosed with more
than one clinical disease in early lactation.
The incidence of subclinical hypocalcemia changed according to threshold
selected. It was lowest when based on whole blood iCa ≤ 1.0 mM, intermediate when
tCa ≤ 2.0 mM, and highest when based on tCa < 2.15 mM (Table 3-11). Nevertheless,
despite the threshold used, treatments did not influence the incidence of subclinical
hypocalcemia postpartum. Similarly, the daily prevalence of subclinical hypocalcemia
changed with threshold selected and followed the same pattern as incidence of
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subclinical hypocalcemia (Table 3-11). The daily prevalence of subclinical hypocalcemia
declined (P < 0.001) with day postpartum regardless of threshold used, but neither
treatment nor interaction between treatment and day affected the daily prevalence of
subclinical hypocalcemia (Figure 3-5).
By 42 d postpartum, 7.1% of the cows enrolled in the experiment had been sold
or died, and this number increased to 21.2% by 305 d postpartum (Table 3-11).
Duration of feeding or level of prepartum DCAD had no effect on the risk of cows
leaving the herd.
Reproduction
Of the 113 cows enrolled in the experiment considered for analyses of
reproductive performance, 101 (89.3%) received at least 1 AI postpartum. Treatment
did not influence the proportion of cows receiving AI (Table 3-12). Because cows were
subjected to timed AI, days to first AI did not differ among treatments. Pregnancy at first
AI did not differ with treatment, but pregnancy per AI after all AI were completed was
greater (P = 0.03) for Short than Long (Short = 35.0 vs. Long = 22.6%), which tended (P
= 0.08) to increase the proportion of pregnant cows by 305 d postpartum (Short = 76.0
vs. Long = 60.0%). In fact, the rate of pregnancy was 55% greater (P = 0.06) in cows
fed Short than those fed Long (Table 3-13; Figure 3-5A), which reduced the mean and
median days to pregnancy. Level of DCAD did not influence reproduction in dairy cows.
Discussion
According to the USDA (2008; 2016), approximately 30% of the dairy farms in
the United States use acidogenic diets to prevent hypocalcemia, and 60% separate
prepartum cows into far-off and close-up pens during the dry period. Recommended
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range of DCAD in diets for prepartum cows has been suggested as -50 to -150 mEq/kg
(NRC, 2001), although the ideal DCAD for prepartum cows has not been established to
optimize postpartum health and performance. Furthermore, some producers might opt
to group prepartum cows together during the entire dry period and limited data suggest
that feeding acidogenic diets longer than 21 d might not be detrimental to early
postpartum performance (Weich et al., 2013; Wu et al., 2014). Therefore, the treatments
adopted in the current experiment were designed to reflect those management practices
when feeding prepartum dairy cows. Increasing the duration of feeding acidogenic diets
prepartum from the traditional 21 to 42 d before calving reduced gestation length and
milk yield, and compromised reproductive performance regardless of the level of DCAD
fed. Concurrently, reducing the level of DCAD from -70 to -180 mEq/kg in the prepartum
diets decreased prepartum DM intake and produced a more exacerbated metabolic
acidosis which attenuated the decrease of iCa concentration in blood at calving, but
only affected colostrum yield at the first milking, with no impact on productive
performance, health or reproduction in dairy cows.
Acidogenic diets are well known for their positive impacts on reducing the risk of
hypocalcemia in dairy cows (Ender et al., 1971; Block, 1984), but they are also known
to reduce intake prepartum. Charbonneau et al. (2006) demonstrated a linear decrease
in DM intake with a reduction in DCAD. Therefore, the reduction in DM intake either
between -42 and -22 d prepartum, when cows were fed three distinct diets, or in the last
21 d prepartum was an expected response. The cause for this reduction has been
widely suggested as caused by a potential palatability issue with acidogenic salts,
although in many cases experiments have used high Cl and S products and not
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necessarily a particular salt (Martinez et al., 2018a). Vagnoni and Oetzel (1998)
supplemented cows with different acidogenic products to reduce the DCAD of diets fed
to dry cows and showed a decrease in DM intake compared with cows not fed
acidogenic products, regardless of the source of strong anions fed. It was suggested
that the decrease in DM intake may be explained by the “discomfort” generated by the
metabolic acidosis rather than the palatability of the acidogenic products. Recently, our
group showed that the reduction in appetite and changes in feeding behavior are
induced by the changes in acid-base status and not by feeding acidogenic product per
se (Zimpel et al., 2018). Pregnant dry cows were assigned to 5 different diets in a
duplicated 5 x 5 Latin square experiment with diets differing in level of DCAD, content of
acidogenic products and level of Cl salts. The authors demonstrated that depression in
intake was not related to the inclusion of acidogenic product, but by the effect of
metabolic acidosis. When cows were fed acidogenic product, but alkalogenic salts were
added to buffer the acidogenic diet, it prevented the decline in DM intake (Zimpel et al.,
2018). In consequence to the decrease in DM intake, especially during the last 3 weeks
of the dry period, cows fed the -180 DCAD had less caloric intake and consequently, a
smaller energy balance that led to a greater body condition loss prepartum.
Increasing the duration of feeding acidogenic diets prepartum from 21 to 42 d
reduced milk yield in the first 42 d postpartum by 2.5 kg/d. Nevertheless, yields of 3.5%
FCM and ECM did not differ with treatment. Others have fed prepartum cows
acidogenic diets up to 42 d prepartum and found no differences in early lactation milk
yield by extending the duration of feeding past 21 d (Weich et al., 2013; Wu et al.,
2014). Although cows in Weich et al. (2013) and Wu et al. (2014) were fed diets with
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DCAD of -150 and -200 mEq/kg, respectively, the responses in acid-base balance were
more moderate than those observed in the current experiment in cows fed the -180
mEq/kg diet. Also, cows fed Long had gestation length decreased by 2 d compared with
those fed Short, and it is possible that a reduction in gestation length might have
affected mammogenesis and subsequent milk yield (Capuco et al., 1997; Vieira-Neto et
al., 2017a). The last few weeks of gestation determine most of mammary development,
and number of milk secreting cells depend on proper length of dry period. Capuco et al.
(1997) characterized the sequence of cytological changes of bovine mammary gland
during the weeks after milk cessation and demonstrated that nearly all alveolar cells
display characteristics of cells competent for milk synthesis and milk production during
the last week prepartum. The mechanism that underlies the decrease in milk yield from
a longer exposure to metabolic acidosis remains unclear, but it is possible that the 2 d
less of dry period that the cows fed Long might have affected the cell differentiation of
the mammary epithelial cells into secretory cells, and in consequence affected milk
yield.
Another possibility is that longer exposure to metabolic acidosis might have
influenced either prolactin signaling (Yan et al., 2013) or the growth hormone/insulin-like
growth factor-1 endocrine axis (Challa et al., 1993b) that is important to mammary
development (Neville and Watters, 1983; Akers et al., 1990). In mouse cell culture
systems transfected with human prolactin and growth hormone receptors, moderate
acidosis at pH 6.8 disrupted prolactin receptor signaling (Yan et al., 2013), and the
authors suggested that proton-induced disruption of prolactin signaling occurred by
impeding ligand-receptor binding in tissues. Metabolic acidosis has been found to inhibit
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growth hormone secretion in rats (Challa et al., 1993b), and impair growth
hormone/insulin like growth factor-1 endocrine axis function in humans (Challa et al.,
1993a; Brüngger et al., 1997). Therefore, it is plausible to suggest that the prolonged
acid-base disturbance caused by feeding the acidogenic diets for 42 d might have
influenced mammogenesis either by influencing prolactin signaling in the mammary
tissue or by reducing growth hormone/insulin-like growth factor-1 either directly or by
the decreased DM intake and the less favorable nutrient balance. Nevertheless, it is
important to point out that after correcting for milk components, the yields of 3.5% FCM
and ECM did not differ with increased exposure to the acidogenic diets prepartum. In
fact, only yield of lactose was less with feeding the acidogenic diets for 42 d, with no
changes in content or yield of fat or protein.
Few experiments have evaluated the effect of level of DCAD on yield and
composition of colostrum. Recently, Martinez et al. (2018a) fed prepartum cows diets
with approximately +130 or -130 mEq/kg and demonstrated that reducing the DCAD of
prepartum diets did not influence colostrum yield or composition. Weich et al. (2013)
showed that colostrum yield was unaffected by feeding acidogenic diets containing -150
mEq/kg either for the last 21 or 42 d of gestation. In the present experiment, reducing
the DCAD from -70 to -180 mEq/kg reduced first milking colostrum yield by 1.4 kg/d
suggesting perhaps that a more exacerbated metabolic acidosis with subsequent
reduction in prepartum DM intake might have effects on colostrum synthesis. Cows fed
the -180 mEq/kg diet had measures of acid-base balance that were less than those of
Weich et al. (2013) or Martinez et al. (2018a) reported in Rodney et al. (2018).
Prepartum blood pH, base excess, and bicarbonate were all less in cows fed -180
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mEq/kg in the present experiment than those fed acidogenic diets reported by Rodney
et al. (2018), and urinary pH in cows fed -180 mEq/kg was less than those reported by
Rodney et al. (2018) or Weich et al. (2003). Therefore, it is possible that the more
acidogenic diet fed in the current experiment might have influenced nutrient intake
because of the depression in DM intake or induced a more exacerbated metabolic
acidosis that is detrimental to colostrum synthesis.
Bertics et al. (1992) found a relationship between reduced DM intake prepartum,
which resulted in a more negative energy balance, with a decrease in milk yield
postpartum. Therefore, one possible explanation for the reduction in colostrum yield
might have been the more negative energy balance the cows fed the -180 mEq/kg
treatment had during the last week of gestation compared with cows fed the -70 mEq/kg
diet. Although yield of first milking colostrum was depressed in cows fed -180 compared
with -70 mEq/kg, the smaller DCAD did not affect yields of milk or milk components in
the first 42 d of lactation. Our results suggest that the negative effects of a more
exacerbated metabolic acidosis and subsequent reduced nutrient intake during late
gestation is only present in the immediate postpartum and reduces colostrum yield, but
it does not compromise subsequent lactation performance.
Acidogenic diets induce a typical compensated metabolic acidosis with a
moderate decline in blood pH, reduced blood bicarbonate and base excess, increased
net acid urinary excretion, and reduced blood pCO2 (Vagnoni and Oetzel, 1998;
Charbonneau et al., 2006). The decrease in blood pH from feeding diets with negative
DCAD occurs because the increased absorption of strong anions such as chloride leads
to either a loss of bicarbonate or a gain of hydrogen protons to maintain electrical
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neutrality in cells. The loss of bicarbonate results in more free hydrogen ions, which
consequently reduces base excess and blood pH (Riond, 2001; Constable, 2014). This
decrease in blood pH triggers a series of compensatory mechanisms, one of which is
controlled by the respiration with increases in exhaled CO2, thereby reducing tCO2
concentrations in blood. Also, renal compensation occurs with excess of acid excreted
in the urine resulting in reduced urinary pH, all of which were observed when cows were
fed the acidogenic diets in the present experiment. Because cows fed the -180 mEq/kg
treatment received a more acidogenic diet, it was anticipated that their responses in
acid-base balance would be more exacerbated than those receiving the -70 mEq/kg
diet.
Concentrations of iCa in blood prepartum and on the day of calving were greater
in cows fed the -180 than the -70 mEq/kg, but these difference did not influence the risk
of milk fever or incidence and daily prevalence of subclinical hypocalcemia. Two of 58
cows (3.5%) fed Short developed milk fever postpartum, and this incidence is within the
expected when cows are fed acidogenic diets in the last 21 d of gestation (USDA, 2007;
Lean et al., 2006; Reinhardt et al., 2011). It is well established that as the prepartum
DCAD decreases, blood iCa increases and risk of milk fever decreases (Charbonneau
et al., 2006; Lean et al., 2006). Because all cows in the experiment were fed acidogenic
diets prepartum that induced a compensated metabolic acidosis, it is not surprising that
risk of hypocalcemia did not differ among treatments, and incidence was very low. In
fact, treatment did not affect the incidence of any of the diseases evaluated, risk of
morbidity or multiple diseases. Hypocalcemia is known for being a “gateway” disease by
predisposing cows to other peripartum problems (Curtis et al., 1985; Martinez et al.,
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2012; Ribeiro et al., 2013). Because acidogenic diets are fed to improve mineral
metabolism with the onset of lactation (Ender et al., 1971; Block, 1984), and risk of
hypocalcemia did not differ with treatment, it is not surprising that risk of diseases did
not differ with treatments.
Pregnancy per AI after all AI was greater for cows fed Short than those fed Long.
The reduced pregnancy per AI resulted in a tendency for reduced pregnancy rate and
extended days open. One possible explanation for the decreased reproductive
performance of the cows fed Long compared with those fed Short is the longer
exposure to the metabolic acidosis that decreased the DM intake during the dry period.
The decrease in intake reduced nutrient and energy intake, placing the cows in a more
negative energy balance prepartum. These cows also had numerically greater decrease
in BW postpartum concurrent with less milk yield, perhaps suggesting that DM intake
was less in early lactation. Because postpartum DM intake was not measured, we can
only speculate what might have happened with nutrient intake on that period. It is well
characterized that reduced nutrient intake and more negative energy balance disrupts
reproduction by delaying first postpartum ovulation and compromising pregnancy per AI
(Staples et al., 1990). Wathes et al. (2007) proposed that the decreased reproductive
performance in cows in more negative nutrient balance is in part linked to reduced
systemic concentrations of insulin-like growth factor 1, which is likely to impact ovarian
activity and early embryo development. Perhaps, the reduced nutrient intake observed
during the dry period when cows were fed acidogenic diets in Long might have also
reflected in less intake postpartum, which could have affected subsequent reproductive
performance. Another possible explanation is that cows fed acidogenic diets for 42 d
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had shorter gestation length, and that has been associated with impaired reproductive
performance (Norman et al., 2011; Vieira-Neto et al., 2017). Even though the negative
association between short gestation length and reduced reproductive performance has
been shown, the underlying mechanisms remain unclear. Finally, it is possible that
prolonged acidosis for 42 d prepartum might have influenced tissue metabolism that has
ramifications to reproduction in the subsequent lactation.
Final Remarks
Feeding diets with negative DCAD successfully induced a compensated metabolic
acidosis in dairy cows prepartum regardless of the duration of feeding, and the acidosis
was more exacerbated in those fed the -180 than -70 mEq/kg of DM. Cows fed the
more acidogenic diet had increased iCa concentrations prepartum and on the day of
calving, but no treatment effects were observed on the incidence or daily prevalence of
subclinical hypocalcemia postpartum. Reducing the DCAD of the diets decreased DM
intake prepartum especially in cows fed -180 mEq/kg of DM. This decrease in DM
intake resulted in a more negative energy balance in the last weeks of gestation. These
same cows had less colostrum yield at the first postpartum milking perhaps as
consequence of less nutrient intake during the last weeks of gestation. Nevertheless,
feeding a more acidogenic diet at -180 mEq/kg did not influence yields of milk, milk
components, health, or reproduction in dairy cows compared with cows fed a diet with -
70 mEq/kg, thereby suggesting that this range of DCAD is likely adequate for diets fed
to prepartum cows. Extending the duration of feeding diets with negative DCAD had
minor impacts on blood iCa and measures of acid-base status pre- and postpartum, but
reduced milk yield in the first 42 d postpartum and pregnancy per AI in all AI in the first
305 d of lactation. It is possible that the reduction in milk yield and reproductive
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performance caused by feeding acidogenic diets for 42 d prepartum might have a
common underlying cause, although the current experiment does not allow us to identify
it. Cows fed Long had decreased DM intake and reduced intake prepartum has been
linked to depressed postpartum performance, although no cause and effect has been
established. Less DM intake with feeding acidogenic diets reduced energy balance
prepartum, and cows fed Long had numerically more body weight loss concurrent with
less milk yield, perhaps suggesting that the worse energy balance continued after
calving.
In summary the data present in this experiment suggest that extending the duration
of feeding acidogenic diets up to 42 d prepartum impairs the productive and
reproductive performance of the cow in the subsequent lactation. Further studies are
required to investigate the underlying mechanism by which a longer duration of feeding
influences production and reproduction in dairy cows.
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Table 3-1. Characteristics of cows enrolled in the experiment according to treatment (mean ± SD)
Treatment1
Item Short -70 Short -180 Long -70 Long -180
Lactation prepartum
Mean ± SD 1.90 ± 0.94 1.83 ± 1.10 1.89 ± 0.96 2.00 ± 1.16
Primiparous, n 12 13 11 12
Multiparous, n 17 16 17 16
Body weight, kg 708.0 ± 86.5 745.2 ± 68.0 749.6 ± 86.0 724.1 ± 81.4
Body condition score, 1 to 5 3.64 ± 0.39 3.69 ± 0.36 3.63 ± 0.43 3.61 ± 0.33
Gestation length, d 277.5 ± 4.4 276.9 ± 4.7 275.8 ± 5.4 274.8 ± 5.1
Prepartum
Days dry 55.2 ± 16.0 55.1 ± 13.9 52.9 ± 8.3 53.1 ± 9.8
Days on experiment 44.1 ± 6.3 43.8 ± 6.1 44.1 ± 6.2 43.3 ± 6.1
Days fed negative DCAD 20.9 ± 4.3 20.4 ± 4.7 43.5 ± 6.0 43.0 ± 6.5
305-d milk, kg/d 34.0 ± 6.0 33.2 ± 4.9 32.3 ± 5.5 33.5 ± 4.5
Calf
Singleton female, n 11 8 10 14
Singleton male, n 16 19 15 14
Twin, n 2 2 3 0
1 From day -42 to -22 relative to calving, cows in treatments Short -70 and Short -180 were fed a diet with
a DCAD of +110 mEq/kg, whereas cows in Long -70 were fed a containing -70 mEq/kg and cows in Long -
180 were fed a diet containing -180 mEq/kg.
97
Table 3-2. Ingredient composition and nutrient content of diets fed during the prepartum and postpartum periods Prepartum diets1
Ingredients, % of DM +110 -70 -180 Lactation
Alfalfa hay --- --- --- 14.7
Corn silage 34.2 34.2 34.2 33.8
Triticale silage 20.4 20.4 20.4 ---
Bermuda hay 6.7 6.7 6.7 ---
Wheat straw 13.8 13.8 13.8 ---
Citrus pulp 7.7 7.1 6.7 7.8
Soybean meal, solvent extract 13.1 8.5 5.8 12.1
Acidogenic supplement2 --- 5.2 8.3 ---
Corn grain, finely ground --- --- --- 10.7
Brewer’s grains, wet --- --- --- 9.3
Soybean hulls --- --- --- 4.4
Saturated free fatty acids3 --- --- --- 1.7
Prepartum mineral-vitamin mixture4 4.2 4.2 4.2 ---
Postpartum mineral-vitamin mixture5 --- --- --- 5.0
Mycotoxin binder6 --- --- --- 0.5
Nutrient content, mean ± SD7
NEL,8 Mcal/kg 1.46 1.45 1.45 1.66
Organic matter, % 92.5 ± 0.5 92.3 ± 0.4 92.4 ± 0.3 91.0 ± 0.9
98
Table 3-2. Continued
Prepartum diets1
Ingredients, % of DM +110 -70 -180 Lactation
Crude protein, % 14.9 ± 0.8 14.7 ± 0.4 14.6 ± 0.6 17.4 ± 0.5
Acid detergent fiber, % 29.4 ± 1.4 28.9 ± 1.2 29.1 ± 1.1 22.5 ± 2.4
Neutral detergent fiber, % 43.1 ± 1.7 43.7 ± 1.5 43.8 ± 1.5 31.6 ± 1.9
Forage neutral detergent fiber, % 39.3 ± 1.7 39.3 ± 1.7 39.3 ± 1.7 20.0 ± 1.6
Nonfibrous carbohydrates,9 % 31.7 ± 1.3 31.1 ± 1.6 31.1 ± 1.9 37.3 ± 3.3
Starch, % 12.3 ± 0.4 12.6 ± 0.5 12.9 ± 0.6 20.5 ± 2.6
Fatty acids, % 2.8 ± 0.2 2.8 ± 0.1 2.8 ± 0.1 4.0 ± 0.1
Ca, % 0.67 ± 0.07 0.64 ± 0.05 0.62 ± 0.05 1.00 ± 0.38
P, % 0.33 ± 0.01 0.33 ±0.02 0.33 ± 0.03 0.38 ± 0.02
Mg, % 0.44 ± 0.06 0.47 ± 0.06 0.48 ± 0.03 0.40 ± 0.03
K, % 1.54 ± 0.10 1.49 ± 0.09 1.46 ± 0.09 1.65 ± 0.09
S, % 0.29 ± 0.03 0.40 ± 0.03 0.47 ± 0.03 0.21 ± 0.01
Na, % 0.08 ± 0.03 0.11 ± 0.03 0.13 ± 0.04 0.55 ± 0.03
Cl, % 0.50 ± 0.07 0.86 ± 0.07 1.11 ± 0.03 0.66 ± 0.05
DCAD,10 mEq/kg +109 ± 35 -66 ± 17 -176 ± 20 346 ± 19
1 Cows were fed the following diets according to treatment: Short -70 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a
diet with -70 mEq/kg from 255 d of gestation to calving; Short -180 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a diet
with -180 mEq/kg from 255 d of gestation to calving; Long -70 = diet containing -70 mEq/kg from 232 d of gestation to calving; Long -180 = diet
containing -180 mEq/kg from 232 d of gestation to calving.
2 Bio-Chlor (fermentation product containing dried condensed extracted glutamic acid fermentation product, dried condensed corn
fermentation solubles, processed grain by-products, and magnesium chloride; Arm & Hammer Animal Nutrition, Princeton, NJ).
3 Energy-Booster Mag (fat supplement containing 95.8% fatty acids and 2.3% Mg, Milk Specialties Global, Eden Prairie, MN).
99
4 Contains (DM basis) 3.7% Ca, 0.9% P, 5.5% Mg, 0.9% K, 2.3% S, 1.1% Na, 1.6% Cl, and per kg of DM, 724 mg of Zn, 165 mg of Cu, 543 mg of
Mn, 9 mg of Se, 16 mg of I, 4 mg of Co, 232,000 IU of vitamin A, 67,000 IU of vitamin D3, 3,300 IU of vitamin E, 750 mg of monensin, and 54 g of
choline ion in a rumen-protected form.
5 A mixture containing 20% blood meal enriched with rumen-protected lysine and methionine (LysAAMet, Perdue Ag Solutions, LLC, Salisbury, MD).
Contains (DM basis) 19.1% CP, 6.3% Ca, 2.0% P, 3.4% Mg, 8.3% K, 0.3% S, 9.3% Na, 5.3% Cl, and per kg of DM, 500 mg of Zn, 115 mg of Cu,
421 mg of Mn, 6.4 mg of Se, 11.1 mg of I, 3.9 mg of Co, 110,000 IU of vitamin A, 27,000 IU of vitamin D3, 1300 IU of vitamin E, 380 mg of monensin
(Rumensin 90, Elanco Animal Health, Eli Lilly and Co, Indianapolis, IN), 22 mg of biotin, and 16 g of choline ion in a rumen-protected form (Reashure,
Balchem Co., New Hampton, NY).
6 Novasil Plus (BASF Corp. Florham Park, NJ).
7 Samples of ingredients were collected weekly and composited each month for chemical analyses. A total of 5 samples of each ingredient was
analyzed for chemical composition.
8 Estimated using NRC (2001) according to chemical analyses of dietary ingredients and adjusted for DM intakes of 12 kg/d prepartum and 22 kg/d
postpartum.
9 Nonfibrous carbohydrates: Organic matter - (crude protein + fatty acids + neutral detergent fiber).
10 DCAD = dietary cation-anion difference calculated as follows: [(mEq of K) + (mEq of Na)] – [(mEq of Cl) + (mEq of S)].
100
Table 3-3. Effects of level of dietary cation-anion difference (DCAD) on measures of energy status from d -42 to -22 relative to calving, blood acid-base status and concentrations of minerals in Holstein cows1
Treatment, DCAD as mE/kg P-value2
Item +110 -70 -180 Treatment Linear Quadratic
Cows, n 58 28 28 --- --- ---
DM intake, kg/d 11.5 ± 0.3 10.7 ± 0.4 10.2 ± 0.4 0.01 0.02 0.55
Caloric intake, Mcal NE/d 16.7 ± 0.5 15.5 ± 0.6 14.8 ± 0.7 0.02 0.01 0.48
NE balance, Mcal/d 1.2 ± 0.5 -0.1 ± 0.6 -0.5 ± 0.7 0.03 0.02 0.36
Body weight, Kg 752.8 ± 12.5 759.0 ± 15.5 734.8 ± 17.0 0.44 0.26 0.42
Body condition, 1 to 5 3.73 ± 0.06 3.67 ± 0.07 3.69 ± 0.08 0.65 0.66 0.49
Whole blood3
pH 7.426 ± 0.011 7.396 ± 0.015 7.397 ± 0.014 0.11 0.13 0.24
Total CO2, mM 27.8 ± 0.6 27.7 ± 0.8 24.6 ± 0.8 0.001 < 0.001 0.17
Saturation of O2, % 59.6 ± 2.8 58.6 ± 3.9 67.5 ± 3.9 0.15 0.06 0.34
PCO2, mm Hg 40.6 ± 1.0 43.4 ± 1.4 38.2 ± 1.4 0.02 0.07 0.02
PO2, mm Hg 31.6 ± 2.1 30.9 ± 2.9 35.8 ± 2.8 0.34 0.17 0.46
Bicarbonate, mM 26.6 ± 0.6 26.4 ± 0.8 23.6 ± 0.8 0.004 0.001 0.25
Base excess, mM 2.12 ± 0.69 1.59 ± 0.95 -1.17 ± 0.94 0.01 0.004 0.47
Ionized Ca, mM 1.245 ± 0.012 1.227 ± 0.017 1.248 ± 0.017 0.55 0.72 0.28
Na, mM 140.6 ± 0.3 140.7 ± 0.4 140.7 ± 0.4 0.96 0.88 0.85
K, mM 4.05 ± 0.08 4.11 ± 0.10 4.05 ± 0.10 0.83 0.89 0.54
Glucose, mM 3.65 ± 0.06 3.69 ± 0.09 3.75 ± 0.09 0.63 0.35 0.95
Urine pH 8.05 ± 0.06 6.52 ± 0.07 5.48 ± 0.08 < 0.001 < 0.001 < 0.001
1 From day -42 to -22 relative to calving, cows in treatments Short -70 and Short -180 were fed a diet with a DCAD of +110 mEq/kg, whereas cows
101
in Long -70 were fed a containing -70 mEq/kg and cows in Long -180 were fed a diet containing -180 mEq/kg.
2 Treatment = effect of treatment (+110 vs. -70 vs. -180 mEq/kg); Linear = orthogonal polynomial contrast for the linear effect of DCAD; Quadratic =
orthogonal polynomial contrast for the quadratic effect of DCAD.
3 Analysis performed in jugular whole blood sampled at 250 d of gestation, approximately 25 d before calving. PO2 = partial pressure of O2; PCO2
= partial pressure of CO2.
102
Table 3-4. Effects of duration (DUR) of prepartum feeding and level of dietary cation-anion difference (DCAD) on measures of energy status in the last 21 d of gestation in Holstein cows1
Short Long P-value2
Item -70 -180 -70 -180 SEM DUR DCAD DUR x DCAD
DM intake, kg/d 11.1 9.7 10.5 9.6 0.5 0.38 0.005 0.45
Caloric intake, Mcal NE/d 16.0 14.0 15.1 13.9 0.7 0.43 0.007 0.51
NE balance, Mcal/d 0.23 -2.16 -0.89 -1.90 0.72 0.49 0.007 0.27
Body weight
Kg 753.8ab 781.3a 771.6ab 747.5b 14.2 0.50 0.89 0.03
Change wk -6 to -1, kg/d 1.02a 0.44b 0.46b 0.70ab 0.20 0.37 0.29 0.01
Body condition
Score, 1 to 5 3.63 3.64 3.64 3.59 0.07 0.73 0.77 0.65
Change wk -6 to -1 -0.124 -0.178 -0.081 -0.221 0.063 0.99 0.06 0.40
1 Cows were fed the following diets according to treatment: Short -70 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a
diet with -70 mEq/kg from 255 d of gestation to calving; Short -180 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a diet
with -180 mEq/kg from 255 d of gestation to calving; Long -70 = diet containing -70 mEq/kg from 232 d of gestation to calving; Long -180 = diet
containing -180 mEq/kg from 232 d of gestation to calving.
2 DUR = effect of feeding duration (42 vs. 21 d); DCAD = effect of level of DCAD (-70 vs. -180); DUR x DCAD = effect of interaction between DUR
and DCAD.
a,b Superscripts in the same row differ after adjustment by the method of Tukey.
103
Table 3-5. Effects of duration (DUR) of prepartum feeding and level of dietary cation-anion difference (DCAD) on measures of blood acid-base balance, and urinary pH and excretion of minerals in Holstein cows prepartum1
Short Long P-value2
Item -70 -180 -70 -180 SEM DUR DCAD DUR x DCAD
Blood3
pH 7.424 7.385 7.417 7.381 0.009 0.47 < 0.001 0.86
Total CO2, mM 27.2 24.0 26.6 25.0 0.7 0.72 < 0.001 0.14
Saturation of O2, % 58.1 59.4 59.5 57.7 2.5 0.94 0.89 0.47
PCO2, mm Hg 40.1 37.8 39.5 39.9 0.9 0.36 0.22 0.07
PO2, mm Hg 30.1 31.8 32.0 31.3 1.2 0.50 0.64 0.22
Bicarbonate, mM 26.2 22.6 25.9 23.8 0.7 0.47 < 0.001 0.18
Base excess, mM 1.75 -2.26 1.07 -1.43 0.78 0.91 < 0.001 0.23
Urine
pH4 6.46 5.62 6.48 5.56 0.14 0.81 < 0.001 0.64
Creatinine,5 mg/L 642 519 673 508 66 0.84 < 0.001 0.62
L/d5 33.5 42.8 32.6 43.0 4.3 0.88 < 0.001 0.82
Ca,5 mg/L 233 319 259 318 31 0.64 0.007 0.63
Ca,5 g/d 6.48 11.06 6.86 11.06 0.91 0.81 < 0.001 0.81
Mg,5 mg/L 193 175 211 165 31 0.85 0.07 0.39
Mg,5 g/d 6.24 7.58 6.69 6.32 0.84 0.58 0.50 0.24
1 Cows were fed the following diets according to treatment: Short -70 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a
diet with -70 mEq/kg from 255 d of gestation to calving; Short -180 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a diet
with -180 mEq/kg from 255 d of gestation to calving; Long -70 = diet containing -70 mEq/kg from 232 d of gestation to calving; Long -180 = diet
containing -180 mEq/kg from 232 d of gestation to calving.
2 DUR = effect of feeding duration (42 vs. 21 d); DCAD = effect of level of DCAD (-70 vs. -180); DUR x DCAD = effect of interaction between DUR
104
and DCAD (Short -70 plus Long -180 vs. Short -180 vs. Long -70).
3 Jugular whole blood sampled and analyzed at 268 and 272 d of gestation, corresponding to -10 and -6 d relative to calving.
4 Urine sampled and analyzed from 256 d of gestation to calving.
5 Urine sampled and analyzed in the last 2 weeks of gestation.
105
Table 3-6. Effects of duration (DUR) of prepartum feeding and level of dietary cation-anion difference (DCAD) on blood concentrations of minerals and metabolites in Holstein cows prepartum1
Short Long P-value2
Item -70 -180 -70 -180 SEM DUR DCAD DUR x DCAD
Blood iCa, mM3 1.236 1.272 1.230 1.271 0.013 0.78 0.002 0.83
Plasma tCa, mM4 2.41 2.40 2.39 2.36 0.03 0.13 0.34 0.73
Plasma tMg, mM4 0.75 0.72 0.75 0.76 0.01 0.25 0.66 0.27
Plasma tP, mM4 1.74b 1.82ab 1.83a 1.77ab 0.05 0.52 0.66 0.008
Blood Na, mM3 143.0 143.6 143.2 143.5 0.4 0.99 0.27 0.77
Blood K, mM3 4.00 4.03 4.15 4.13 0.09 0.12 0.95 0.76
Plasma glucose, mM4 3.58 3.59 3.62 3.64 0.06 0.88 0.65 0.11
Plasma NEFA, mM4 0.260ab 0.314a 0.275ab 0.239b 0.027 0.20 0.76 0.05
Plasma BHB, mM4 0.693 0.732 0.699 0.666 0.030 0.21 0.95 0.15
1 Cows were fed the following diets according to treatment: Short -70 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a
diet with -70 mEq/kg from 255 d of gestation to calving; Short -180 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a diet
with -180 mEq/kg from 255 d of gestation to calving; Long -70 = diet containing -70 mEq/kg from 232 d of gestation to calving; Long -180 = diet
containing -180 mEq/kg from 232 d of gestation to calving.
2 DUR = effect of feeding duration (42 vs. 21 d); DCAD = effect of level of DCAD (-70 vs. -180); DUR x DCAD = effect of interaction between DUR
and DCAD (Short -70 plus Long -180 vs. Short -180 vs. Long -70).
3 Jugular blood sampled on d -10 and -6 relative to calving and analyzed for concentrations of iCa, Na, and K.
4 Blood sampled by puncture of coccygeal vessels on d -14, -12, -10, -8, -6, -4, and -2 relative to calving and plasma analyzed for concentrations of
tCa, tMg, tP, glucose, NEFA, and BHB.
a,b Superscripts in the same row differ after adjustment by the method of Tukey.
106
Table 3-7. Effects of duration (DUR) of prepartum feeding and level of dietary cation-anion difference (DCAD) on colostrum yield and composition in Holstein cows1
Short Long P-value2
Item -70 -180 -70 -180 SEM DUR DCAD DUR x DCAD
First milking
Yield, kg 6.79 4.88 6.30 5.41 0.88 0.98 0.04 0.45
Content
Fat, % 4.97 5.53 5.06 5.18 0.47 0.76 0.41 0.59
True protein, % 13.0 13.9 14.3 14.1 0.5 0.09 0.44 0.22
Lactose, % 3.42 3.39 3.37 3.34 0.08 0.49 0.67 0.99
Solids not fat, % 17.8 18.6 19.1 18.8 0.5 0.09 0.51 0.19
Total solids, % 22.8 24.2 24.2 24.0 0.8 0.35 0.35 0.23
Net energy, Mcal/kg 1.33 1.43 1.41 1.41 0.05 0.57 0.31 0.30
Ca, g/L 2.29 2.27 2.33 2.36 0.10 0.48 0.95 0.76
Mg, g/L 0.398 0.395 0.381 0.406 0.017 0.85 0.41 0.32
IgG, g/L 76.6 81.2 86.6 87.2 7.3 0.19 0.67 0.75
Somatic cell score 6.23 6.37 6.67 6.60 0.33 0.24 0.89 0.71
Yield
Fat, kg 0.37 0.34 0.34 0.31 0.07 0.59 0.57 0.99
True protein, kg 0.84 0.68 0.92 0.76 0.12 0.39 0.09 0.98
Lactose, kg 0.24 0.17 0.23 0.18 0.03 0.96 0.03 0.66
107
Table 3-7. Continued Short Long P-value2
Item -70 -180 -70 -180 SEM DUR DCAD DUR x DCAD
Solids not fat, kg 1.17 0.92 1.24 1.02 0.16 0.50 0.06 0.91
Total solids, kg 1.54 1.26 1.59 1.33 0.22 0.75 0.12 0.93
Net energy, Mcal 9.11 7.66 9.26 7.88 1.41 0.86 0.18 0.98
Ca, g 14.2 10.6 14.8 11.6 2.1 0.78 0.03 0.76
Mg, g 2.57 1.81 2.42 2.03 0.33 0.89 0.04 0.51
Second milking
Yield, kg 3.03 2.74 2.89 2.78 0.42 0.90 0.58 0.82
Content
Fat, % 5.14 5.20 4.70 4.97 0.51 0.45 0.71 0.82
True protein, % 10.2 11.4 11.3 11.7 0.6 0.17 0.11 0.38
Lactose, % 3.65 3.55 3.61 3.44 0.11 0.45 0.16 0.70
Solids not fat, % 15.1 16.3 16.2 16.4 0.6 0.24 0.17 0.35
Total solids, % 20.2 21.5 20.9 21.4 0.8 0.73 0.25 0.61
Net energy, Mcal/kg 1.20 1.27 1.22 1.26 0.06 0.95 0.30 0.77
Ca, g/L 2.21 2.10 2.28 2.42 0.09 0.01 0.82 0.11
108
Table 3-7. Continued Short Long P-value2
Item -70 -180 -70 -180 SEM DUR DCAD DUR x DCAD
Mg, g/L 0.349ab 0.329b 0.341ab 0.375a 0.016 0.18 0.61 0.06
Somatic cell score 5.99 6.22 6.37 6.54 0.32 0.22 0.47 0.91
Yield
Fat, kg 0.16 0.15 0.14 0.13 0.03 0.44 0.73 0.95
True protein, kg 0.28 0.30 0.32 0.31 0.05 0.62 0.97 0.67
Lactose, kg 0.11 0.10 0.11 0.10 0.02 0.82 0.45 0.94
Solids not fat, kg 0.43 0.44 0.47 0.44 0.07 0.77 0.84 0.76
Total solids, kg 0.59 0.58 0.60 0.56 0.10 0.99 0.80 0.83
Net energy, Mcal 3.47 3.45 3.50 3.29 0.57 0.90 0.82 0.85
Ca, g 6.73 5.93 6.55 6.62 1.03 0.78 0.68 0.63
Mg, g 1.04 0.91 0.97 1.02 0.16 0.86 0.75 0.54
1 Cows were fed the following diets according to treatment: Short -70 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a
diet with -70 mEq/kg from 255 d of gestation to calving; Short -180 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a diet
with -180 mEq/kg from 255 d of gestation to calving; Long -70 = diet containing -70 mEq/kg from 232 d of gestation to calving; Long -180 = diet
containing -180 mEq/kg from 232 d of gestation to calving.
2 DUR = effect of feeding duration (42 vs. 21 d); DCAD = effect of level of DCAD (-70 vs. -180); DUR x DCAD = effect of interaction between DUR
and DCAD (Short -70 plus Long -180 vs. Short -180 vs. Long -70).
a,b Superscripts in the same row differ after adjustment by the method of Tukey.
109
Table 3-8. Effects of duration (DUR) of prepartum feeding and level of dietary cation-anion difference (DCAD) on productive performance in the first 42 d postpartum in Holstein cows1
Short Long P-value2
Item -70 -180 -70 -180 SEM DUR DCAD DUR x DCAD
Milk, kg/d 41.1 39.6 37.5 38.6 1.3 0.03 0.93 0.25
3.5% FCM, kg/d 44.3 43.7 41.8 42.6 1.4 0.15 0.91 0.58
ECM, kg/d 42.8 42.2 40.4 41.2 1.4 0.14 0.91 0.56
Fat
% 4.11 4.27 4.33 4.26 0.11 0.24 0.60 0.22
Yield, kg 1.64 1.64 1.58 1.60 0.06 0.38 0.83 0.86
True protein
% 2.97 3.01 3.05 3.05 0.05 0.17 0.56 0.70
Yield, kg 1.20 1.18 1.12 1.15 0.04 0.14 0.92 0.48
Lactose
% 4.58 4.60 4.60 4.59 0.03 0.91 0.93 0.73
Yield, kg 1.90 1.84 1.74 1.79 0.06 0.04 0.94 0.32
Solids not fat
% 8.41 8.47 8.51 8.51 0.06 0.23 0.65 0.66
Yield, kg 3.45 3.36 3.18 3.27 0.11 0.06 0.99 0.37
Somatic cell score 2.14 1.79 2.19 2.08 0.39 0.59 0.48 0.72
110
Table 3-8. Continued Short Long P-value2
Item -70 -180 -70 -180 SEM DUR DCAD DUR x DCAD
Body weight
Kg 630.9 649.4 640.7 629.1 12.3 0.61 0.73 0.15
Change wk 1 to 6, kg/d -1.56 -1.90 -1.72 -2.02 0.30 0.55 0.16 0.94
Body condition
Score, 1 to 5 3.27 3.36 3.35 3.26 0.06 0.84 0.99 0.14
Change, wk 1 to 6 -0.248 -0.228 -0.257 -0.291 0.08 0.78 0.87 0.49
1 Cows were fed the following diets according to treatment: Short -70 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a
diet with -70 mEq/kg from 255 d of gestation to calving; Short -180 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a diet
with -180 mEq/kg from 255 d of gestation to calving; Long -70 = diet containing -70 mEq/kg from 232 d of gestation to calving; Long -180 = diet
containing -180 mEq/kg from 232 d of gestation to calving.
2 DUR = effect of feeding duration (42 vs. 21 d); DCAD = effect of level of DCAD (-70 vs. -180); DUR x DCAD = effect of interaction between DUR
and DCAD (Short -70 plus Long -180 vs. Short -180 vs. Long -70).
111
Table 3-9. Effects of duration (DUR) of prepartum feeding and level of dietary cation-anion difference (DCAD) on measures of acid-base balance in Holstein cows postpartum1
Short Long P-value2
Item3 -70 -180 -70 -180 SEM DUR DCAD DUR x DCAD
Blood pH 7.451 7.456 7.446 7.455 0.004 0.50 0.09 0.59
Total CO2, mM 30.4 30.6 29.8 31.2 0.4 0.90 0.05 0.12
Saturation of O2, % 61.4 65.3 63.0 62.4 1.3 0.59 0.20 0.08
PCO2, mm Hg 41.6 41.4 41.3 42.2 0.6 0.66 0.50 0.37
PO2, mm Hg 31.2 32.5 32.0 31.5 0.6 0.88 0.43 0.11
Bicarbonate, mM 29.2ab 29.3ab 28.6b 30.0a 0.4 0.94 0.04 0.08
Base excess, mM 5.17 5.52 4.56 6.01 0.41 0.87 0.02 0.15
1 Cows were fed the following diets according to treatment: Short -70 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a
diet with -70 mEq/kg from 255 d of gestation to calving; Short -180 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a diet
with -180 mEq/kg from 255 d of gestation to calving; Long -70 = diet containing -70 mEq/kg from 232 d of gestation to calving; Long -180 = diet
containing -180 mEq/kg from 232 d of gestation to calving.
2 DUR = effect of feeding duration (42 vs. 21 d); DCAD = effect of level of DCAD (-70 vs. -180); DUR x DCAD = effect of interaction between DUR
and DCAD (Short -70 plus Long -180 vs. Short -180 vs. Long -70).
3 Jugular blood sampled and analyzed on d 0, 1, 2, 3, 4 postpartum.
a,b Superscripts in the same row differ after adjustment by the method of Tukey.
112
Table 3-10. Effects of duration (DUR) of prepartum feeding and level of dietary cation-anion difference (DCAD) on blood concentrations of minerals and metabolites in Holstein cows postpartum1
Short Long P-value2
Item -70 -180 -70 -180 SEM DUR DCAD DUR x DCAD
Blood iCa, mM3 1.12 1.13 1.13 1.12 0.01 0.99 0.94 0.53
Plasma tCa, mM4 2.21 2.20 2.20 2.23 0.03 0.65 0.61 0.57
Plasma tMg, mM4 0.725 0.710 0.744 0.745 0.019 0.05 0.57 0.55
Plasma tP, mM4 1.33 1.30 1.37 1.34 0.06 0.44 0.59 0.94
Blood Na, mM3 143.0 143.0 143.2 143.1 0.35 0.62 0.89 0.90
Blood K, mM3 4.12a 3.97b 4.05ab 4.14a 0.08 0.21 0.50 0.008
Plasma glucose, mM5 3.26 3.16 3.19 3.36 0.089 0.30 0.57 0.05
Plasma NEFA, mM5 0.769 0.788 0.704 0.659 0.067 0.09 0.79 0.56
Plasma BHB, mM5 1.50 1.73 1.72 1.41 0.15 0.67 0.72 0.04
1 Cows were fed the following diets according to treatment: Short -70 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a
diet with -70 mEq/kg from 255 d of gestation to calving; Short -180 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a diet
with -180 mEq/kg from 255 d of gestation to calving; Long -70 = diet containing -70 mEq/kg from 232 d of gestation to calving; Long -180 = diet
containing -180 mEq/kg from 232 d of gestation to calving.
2 DUR = effect of feeding duration (42 vs. 21 d); DCAD = effect of level of DCAD (-70 vs. -180); DUR x DCAD = effect of interaction between DUR
and DCAD (Short -70 plus Long -180 vs. Short -180 vs. Long -70).
3 Jugular blood sampled on d 0, 1, 2, 3, and 4 postpartum and whole blood analyzed for concentrations of iCa, Na, and K.
4 Blood sampled by puncture of coccygeal vessels on d 0, 1, 2, 3, 4, 5, and 7 postpartum and plasma analyzed for concentrations of tCa, tMg, and
tP.
5 Blood sampled by puncture of coccygeal vessels on d 0, 1, 2, 3, 4, 5, 7, 14, and 21 and plasma analyzed for concentrations of glucose, NEFA
and BHB.
a,b Superscripts in the same row differ after adjustment by the method of Tukey.
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Table 3-11. Effects of duration (DUR) of prepartum feeding and level of dietary cation-anion difference (DCAD) on health in Holstein cows1
Short Long P-value2
Item3 Incidence, (n/n) -70 -180 -70 -180 DUR DCAD DUR x DCAD
Milk fever, % 1.8 (2/114) 3.5 3.5 0 0 --- --- ---
Retained placenta, % 14.0 (16/114) 13.8 13.8 17.9 10.7 0.92 0.87 0.80
Metritis, % 15.9 (18/113) 20.7 10.3 14.3 18.5 0.75 0.92 0.14
Puerperal metritis, % 8.0 (9/113) 6.9 6.9 7.1 11.1 0.73 0.66 0.66
Mastitis, % 12.4 (14/113) 13.8 10.3 14.3 11.1 0.94 0.73 0.95
Displaced abomasum, % 6.2 (7/113) 3.5 6.9 3.6 11.1 0.64 0.15 0.40
Morbidity, % 32.7 (37/113) 34.5 34.5 25.0 37.0 0.54 0.23 0.35
Multiple diseases, % 15.1 (14/113) 17.2 10.3 21.4 11.1 0.66 0.35 0.89
Subclinical hypocalcemia4
Blood iCa ≤ 1.0 mM, % 36.3 (29/80) 52.4 30.0 26.3 35.0 0.37 0.59 0.17
Plasma tCa ≤ 2.0 mM, % 57.9 (66/114) 62.1 58.6 64.3 46.4 0.61 0.27 0.45
Plasma tCa < 2.15 mM, % 85.1 (97/114) 86.2 79.3 92.9 82.1 0.43 0.19 0.63
Mean daily prevalence5
Blood iCa ≤ 1.0 mM, % --- 12.8 9.1 10.0 13.3 0.91 0.96 0.59
Plasma tCa ≤ 2.0 mM, % --- 31.6 21.7 21.7 17.1 0.21 0.21 0.74
Plasma tCa < 2.15 mM, % --- 50.2 49.1 54.2 44.3 0.95 0.39 0.50
Sold and dead, %
42 d postpartum 7.1 (8/113) 2.7 5.5 8.4 6.1 0.45 0.82 0.54
305 d postpartum 21.2 (24/113) 24.1 13.8 25.0 22.2 0.51 0.37 0.57
1 Cows were fed the following diets according to treatment: Short -70 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a
diet with -70 mEq/kg from 255 d of gestation to calving; Short -180 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a diet
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with -180 mEq/kg from 255 d of gestation to calving; Long -70 = diet containing -70 mEq/kg from 232 d of gestation to calving; Long -180 = diet
containing -180 mEq/kg from 232 d of gestation to calving.
2 DUR = effect of feeding duration (42 vs. 21 d); DCAD = effect of level of DCAD (-70 vs. -180); DUR x DCAD = effect of interaction between DUR
and DCAD (Short -70 plus Long -180 vs. Short -180 vs. Long -70).
3 Data collected until 42 d postpartum.
4 Based on at least one blood sample with value below the indicated threshold with samples collected on d 0, 1, 2, 3 and 4 postpartum.
5 Based on daily risk of subclinical hypocalcemia from 0 to 4 d postpartum according to the respective thresholds.
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Table 3-12. Effects of level of dietary cation-anion difference (DCAD) and duration (DUR) of prepartum feeding on reproduction in Holstein cows1
Short Long P-value2
Item3 -70 -180 -70 -180 DUR DCAD DUR x DCAD
Inseminated, % (n) 89.7 (29) 93.1 (29) 89.3 (28) 85.2 (27) 0.55 0.89 0.51
Days to AI, LSM ± SEM 81.6 ± 3.4 80.0 ± 3.5 80.2 ± 3.4 84.2 ± 3.8 0.64 0.68 0.33
Pregnant,4 % (n)
First AI 41.7 (24) 33.3 (27) 28.0 (25) 34.8 (23) 0.53 0.96 0.44
All AI 35.6 (59) 34.3 (67) 21.3 (75) 23.9 (71) 0.03 0.86 0.71
Pregnant d 305, % (n) 72.4 (29) 79.3 (29) 57.1 (28) 63.0 (27) 0.08 0.46 0.87
Days to pregnancy
LSM ± SEM 150 ± 14 146 ± 14 174 ± 16 151 ± 13 --- --- ---
Median (95% CI) 156 (80 - 176) 139 (80 - 148) 153 (116 - 263) 153 (80 - 201) --- --- ---
1 Cows were fed the following diets according to treatment: Short -70 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a
diet with -70 mEq/kg from 255 d of gestation to calving; Short -180 = diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a diet
with -180 mEq/kg from 255 d of gestation to calving; Long -70 = diet containing -70 mEq/kg from 232 d of gestation to calving; Long -180 = diet
containing -180 mEq/kg from 232 d of gestation to calving.
2 DUR = effect of feeding duration (42 vs. 21 d); DCAD = effect of level of DCAD (-70 vs. -180); DUR x DCAD = effect of interaction between DUR
and DCAD (Short -70 plus Long -180 vs. Short -180 vs. Long -70).
3 Data collected for 305 d postpartum.
4 Pregnancy based on the diagnosis on d 67 after each AI.
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Table 3-13. Cox’s hazard regression model for time to pregnancy according to duration of
prepartum feeding and level of dietary cation-anion difference (DCAD)1 Days to pregnancy2
Item Median (95% CI) Mean ± SEM Pregnant, % AHR3 (95% CI) P-value
Duration4
Short 144 (113 to 156) 149 ± 10 75.9 1.55 (0.98 to 2.45) 0.06
Long 153 (114 to 201) 168 ± 11 60.0 Reference
DCAD
-70 mEq/kg 156 (116 to 165) 162 ± 11 64.9 0.89 (0.57 to 1.38) 0.59
-180 mEq/kg 144 (113 to 179) 156 ± 11 71.4 Reference ---
1 Cows were fed the following diets according to treatment: Short -70 = diet containing +110 mEq/kg from
232 to 254 d of gestation, followed by a diet with -70 mEq/kg from 255 d of gestation to calving; Short -180
= diet containing +110 mEq/kg from 232 to 254 d of gestation, followed by a diet with -180 mEq/kg from
255 d of gestation to calving; Long -70 = diet containing -70 mEq/kg from 232 d of gestation to calving;
Long -180 = diet containing -180 mEq/kg from 232 d of gestation to calving.
2 Pregnancy was based on the diagnosis on d 67 after each AI within the first 305 DIM.
3 AHR = adjusted hazard ratio.
4 Interaction between duration of feeding and level of DCAD was not significant (P = 0.94) and dropped
from the final model.
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Figure 3-1. Prepartum DM intake and urine pH. Panel A, DM intake from d -42 to -22 relative to calving when cows were fed diets with +110, -70, or -180 mEq/kg. Panel B, DM intake from d -21 to -1 relative to calving according to duration of feeding (Short, 21 d; Long, 42 d) and level of DCAD (-70 vs. -180 mEq/kg). Panel C, urine pH from d -42 to -22 relative to calving when cows were fed diets with +110, -70, or -180 mEq/kg. Panel D, urine pH from d -21 to -1 relative to calving according to duration of feeding (Short, 21 d; Long, 42 d) and level of DCAD (-70 vs. -180 mEq/kg). Panel A, interaction between treatment and day (P = 0.008). Panel B, effect of interactions between duration and day (P = 0.15), DCAD and day (P = 0.49), and duration and DCAD and day (P = 0.40). Panel C, effect of interaction between treatment and day (P = 0.11). Panel D, effects of interactions between duration and day (P = 0.03), DCAD and day (P = 0.49), and duration and DCAD and day (P = 0.84). Error bars represent the SEM.
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Figure 3-2. Concentrations of whole blood ionized Ca (iCa, A), plasma total Ca (tCa, B), plasma total Mg (tMg, C), and plasma total P (tP, D) in dairy cows fed prepartum acidogenic diets of Short (21 d) or Long (42 d) duration of feeding and with -70 or -180 mEq/kg. Panel A prepartum, interactions between duration and day (P = 0.95), DCAD and day (P = 0.10), and duration and DCAD and day (P = 0.90); postpartum, interactions between duration and day (P = 0.14), DCAD and day (*, P = 0.04), and duration and DCAD and day (P = 0.46). Panel B prepartum, interactions between duration and day (P = 0.38), DCAD and day (P = 0.31), and duration and DCAD and day (P = 0.004); postpartum, interactions between duration and day (P = 0.31), DCAD and day (P = 0.22), and duration and DCAD and day (P = 0.24). Panel C prepartum, interactions between duration and day (P = 0.10), DCAD and day (P = 0.11), and duration and DCAD and day (P = 0.006); postpartum, interactions between duration and day (P = 0.94), DCAD and day (P = 0.30), and duration and DCAD and day (P = 0.67). Panel D prepartum, interactions between duration and day (P = 0.61), DCAD and day (P = 0.58), and duration and DCAD and day (P = 0.22); postpartum, interactions between duration and day (P = 0.72), DCAD and day (P = 0.53), and duration and DCAD and day (P = 0.76). Error bars represent SEM.
119
Figure 3-3. Concentrations of glucose (A), NEFA (B), and BHB (C) in plasma of dairy cows fed prepartum acidogenic diets of Short (21 d) or Long (42 d) duration of feeding and with -70 or -180 mEq/kg. Panel A prepartum, interactions between duration and day (P = 0.65), DCAD and day (P = 0.88), and duration and DCAD and day (P = 0.65); postpartum, interactions between duration and day (P = 0.95), DCAD and day (P = 0.98), and duration and DCAD and day (P = 0.42). Panel B prepartum, interactions between duration and day (P = 0.88), DCAD and day (P = 0.56), and duration and DCAD and day (P = 0.47); postpartum, interactions between duration and day (P = 0.08), DCAD and day (P = 0.49), and duration and DCAD and day (P = 0.77). Panel C prepartum, interactions between duration and day (P = 0.21), DCAD and day (P = 0.59), and duration and DCAD and day (P = 0.98); postpartum, interactions between duration and day (P = 0.43), DCAD and day (P = 0.93), and duration and DCAD and day (P = 0.45). Error bars represent the SEM.
2.4
2.8
3.2
3.6
4.0
4.4
4.8
5.2
5.6
6.0
Pla
sma
glu
cose
, mM
Short-70
Short-180
Long-70
Long-180
A
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Pla
sma
NE
FA
, m
M
B
0.5
0.8
1.1
1.4
1.7
2.0
2.3
2.6
-14 -12 -10 -8 -6 -4 -2 0 1 2 3 4 5 7 14 21
Pla
sma
BH
B,
mM
Day relative to calving
C
120
Figure 3-4. Yields of milk (panel A) and energy-corrected milk (ECM, panel B), body weight (panel C) and body condition score (panel D) of dairy cows fed prepartum acidogenic diets of Short (21 d) or Long (42 d) duration and with -70 or -180 mEq/kg. Panel A, interactions between duration and day (P = 0.001), DCAD and day (P = 0.96), and duration and DCAD and day (P = 0.96). Panel B, interactions between duration and day (P < 0.001), DCAD and day (P = 0.55), and duration and DCAD and day (P = 0.71). Panel C prepartum, interactions between duration and week (P = 0.66), DCAD and week (P = 0.65), and duration and DCAD and week (P = 0.42); postpartum, interactions between duration and week (P = 0.35), DCAD and week (P = 0.19), and duration and DCAD and week (P = 0.72). Panel D prepartum, interactions between duration and day (P = 0.08), DCAD and week (P = 0.61), and duration and DCAD and week (P = 0.61); postpartum, interactions between duration and week (P = 0.10), DCAD and week (P = 0.66), and duration and DCAD and week (P = 0.78). Error bars represent SEM.
15
20
25
30
35
40
45
50
1 4 7 10 13 16 19 22 25 28 31 34 37 40
Milk y
ield
, kg/d
Day postpartum
Short-70
Short-180
Long-70
Long-180
A
15
20
25
30
35
40
45
50
1 4 7 10 13 16 19 22 25 28 31 34 37 40
EC
M y
ield
, kg/d
Day postpartum
B
580
620
660
700
740
780
820
-3 -2 -1 1 2 3 4 5 6
Body w
eigh
t, k
g
Week relative to calving
C
2.75
3.00
3.25
3.50
3.75
4.00
-3 -2 -1 1 2 3 4 5 6
Body c
on
dit
ion
, 1
to 5
Week relative to calving
D
121
Figure 3-5. Daily risk of subclinical hypocalcemia based on concentration of iCa ≤ 1.0 mM in whole blood
(panel A), tCa ≤ 2.0 mM in plasma (panel B), or tCa < 2.15 mM in plasma (Panel C) in cows fed prepartum acidogenic diets of Short (21 d) or Long (42 d) duration and with -70 or -180 mEq/kg. Panel A, effects of duration (P = 0.91), DCAD (P = 0.96), day (P < 0.001), and interactions between duration and DCAD (P = 0.59), duration and day (P = 0.61), DCAD and day (P = 0.11), and duration and DCAD and day (P = 0.97). Panel B, effects of duration (P = 0.21), DCAD (P = 0.21), day (P < 0.001), and interactions between duration and DCAD (P = 0.73), duration and day (P = 0.15), DCAD and day (P = 0.71), and duration and DCAD and day (P = 0.66). Panel C, effects of duration (P = 0.95), DCAD (P = 0.39), day (P < 0.001), and interactions between duration and DCAD (P = 0.50), duration and day (P = 0.95), DCAD and day (P = 0.88), and duration and DCAD and day (P = 0.32). Error bars represent SEM.
122
Figure 3-6. Survival curves for days from calving to pregnancy according to duration of prepartum feeding (Short vs. Long; Panel A) and level of DCAD (-70 vs. -180 mEq/kg; Panel B).
A
B
123
CHAPTER 4 CONCLUSIONS
The experiment presented in Chapter 3 in this thesis documents the effect of
reducing the dietary cation-anion difference (DCAD) to a more negative value and
extending the duration of feeding from 21 to 42 d prepartum on mineral metabolism,
plasma metabolites, acid-base balance, urinary mineral excretion, and performance of
dairy cows during the pre- and postpartum periods. The findings of the experiment provide
a clear response to a managing problem in the dairy industry. Dairy producers implement
diets with negative DCAD in the last 3 weeks of gestation, but the optimum DCAD remains
unclear. A concern exists with acidogenic diets affecting dry matter (DM) intake feeding
differential diets prepartum imposes the need for pen movements that might further
influence cow behavior and intake. The decrease in DM intake during the peripartum has
been associated with decreased milking performance postpartum and a possible increase
in health issues in early lactation, although no cause and effect has been established.
Despite the well documented reduction in intake prepartum when cows are fed acidogenic
diets, postpartum performance is often improved because diets with negative DCAD
prevent milk fever and hypocalcemia, and cows fed such diets are more capable of coping
with the sudden Ca demands for colostrogenesis and lactation. Because the depression
in intake seems to be mediated by changes in acid-base balance, it is anticipated that
metabolic acidosis induced by diets with negative DCAD will invariably result in less
intake, but the benefits of feeding acidogenic diets prepartum to minimize hypocalcemia
overcome the potential detrimental impacts of reduced DM intake. Because extending the
duration of feeding implicated in providing prepartum cows with acidogenic diets in the
first 21 d of the dry period, it is therefore expected that feeding diets with a negative DCAD
124
throughout the dry period will impose a reduction in DM intake during the entire dry period,
which showed to provide no benefit to postpartum health and performance.
Extending the period of feeding acidogenic diets to 42 d reduced gestation length
and milk yield and depressed reproductive performance in the subsequent lactation.
These responses might be attributed to the extended period of compensated metabolic
acidosis and the reduced nutrient intake during the entire dry period. Cows fed the
acidogenic diets for the entire dry period were in lower energy balance prepartum, which
could have influenced the final stages of mammary development during the dry period.
Also, cows fed the Long treatments had shorter gestation length, approximately 2 d, which
might have had implications to mammary cell proliferation and total secretory tissue
abundance for milk synthesis. Although feeding a single prepartum diet creates
convenience in management, without the need for diet change between the “far-off” and
the “close-up” periods, the results from this experiment provide evidence that no benefits
are observed from such a “simplistic” approach. In fact, some potential negative impacts
might occur from feeding acidogenic diets for 42 d prepartum. Because the reasons for
shorter gestation, reduced milk yield, and longer days open are unclear from this
experiment, further research is needed in this area. The potential for extended period of
compensated metabolic acidosis to influence mechanisms of parturition and to impact
mammary cell development and differentiation are warranted.
Manipulating the mineral composition of prepartum diets to reduce the DCAD
from -70 to -180 mEq/kg induced a more exacerbated metabolic acidosis prepartum that
led to an increase in the concentrations of ionized calcium (iCa) prepartum and on the
day of calving likely because of the effects of metabolic acidosis on parathyroid
125
hormone (PTH) release and the well documented actions of the hormone on bone and
kidney Ca metabolism, and the resulting effects of 1,25(OH)2 vitamin D on gut
absorption of Ca. The increased iCa concentrations induced by cows fed the more
acidogenic diet led to a state of increased urinary excretion of calcium and magnesium.
Postpartum, the reduction in level of DCAD from -70 to -180 mEq/kg influenced
colostrum yield in the first milking, but not in the second milking, with no implications to
composition of colostrum, although the reduced yield of first milking colostrum also
reduced yields of true protein, lactose, and solids-not-fat. Nevertheless, reducing the
DCAD did not influence lactation performance in the first 42 d postpartum, or health and
reproduction. It seems that feeding cows acidogenic diets for 21 d with a DCAD of -70
mEq/kg is sufficient to practically abolish milk fever in parous cows with no additional
benefit from further reducing the DCAD to -180 mEq/kg or extending feeding to 42 d.
Incidence and daily prevalence of subclinical hypocalcemia did not differ with
treatments. Obviously, the present experiment was not designed to determine the
optimal DCAD or the ideal length of feeding given the experimental design and
constraints of number of treatments utilized. Although the ideal DCAD of prepartum
diets remains unknown, the results of the current experiment and those of the published
literature provide evidence that current recommendations of -50 to -150 mEq/kg fed for
the last 21 d of gestation is likely to be adequate to prevent health problems and
improve lactation performance. Ideally, new experiments would be designed to titrate
DCAD with enough cows to determine effects on intake, production, health, and
reproduction. Furthermore, although all animals in the present experiment were parous
126
cows, little is known about the impacts, either positive or negative, of acidogenic diets
on nulliparous cows.
127
LIST OF REFERENCES
Abu Damir, H., M. Phillippo, B.H. Thorp, J.S. Milne, L. Dick, and I.M. Inevison. 1994. Effects of dietary acidity on calcium balance and mobilisation, bone morphology and 1,25 dihydroxyvitamin D in prepartal dairy cows. Res. Vet. Sci. 56:310–318.
Accorsi, P.A., N. Govoni, R. Gaiani, C. Pezzi, E. Seren, and C. Tamanini. 2005. Leptin, GH, PRL, insulin and metabolic parameters throughout the dry period and lactation in dairy cows. Reprod. Domest. Anim. 40:217–223.
Akers, R.M., W.E. Beal, T.B. Mcfadden, and A. V. Capuco. 1990. Morphometric analysis of involuting bovine mammary tissue after 21 or 42 days on non-suckling. J. Anim. Sci. 68:3604–3613.
Allen, L.H. 1982. Calcium bioavailabiltiy and absorption: a review. Am. J. Clin. Nutr. 35:783–808.
Alpers, D.H. 2013. Intraluminal bioavailability of divalent cations. Curr. Opin. Gastroenterol. 29:164–169.
Aschenbach, J.R., N.B. Kristensen, S.S. Donkin, H.M. Hammon, and G.B. Penner. 2010. Gluconeogenesis in dairy cows: The secret of making sweet milk from sour dough. IUBMB Life 62:869–877.
Bannink, A., H. Valk, and A.M. Van Vuuren. 1999. Intake and excretion of sodium, potassium, and nitrogen and the effects on urine production by lactating dairy cows. J. Dairy Sci. 82:1008–1018.
Bauchart, D. 1993. Lipid absorption and transport in ruminants. J. Dairy Sci. 76:3864–3881.
Bauchart, D., D. Gruffat, and D. Durand. 1996. Lipid absorption and hepatic metabolism in ruminants. Proc. Nutr. Soc. 55:39–47.
Bauman, D.E., and W.B. Currie. 1980. Partitioning of nutrients during pregnancy and lactation: A review of mechanisms involving homeostasis and homeorhesis. J. Dairy Sci. 63:1514–1529.
Beaven, G.H., J. Parmar, G.B. Nash, B.M. Bennett, and W.B. Gratzer. 1990. Effect of magnesium ions on red cell membrane properties. J. Membr. Biol. 118:251–257.
Bell, A.W., and D.E. Bauman. 1997. Adaptations of glucose metabolism during pregnancy and lactation. J. Mammary Gland Biol. Neoplasia 2:265–278.
Bell, A.W., R. Slepetis, and U.A. Ehrhardt. 1995. Growth and accretion of energy and protein in the gravid uterus during late pregnancy in Holstein cows. J. Dairy Sci. 78:1954–1961.
128
Bender, D., and P.A. Mayes. 2003. Vitamins and minerals. Pages 481-497 in: Harper’ s Illustrated Biochemistry. 26th edition. R.K. Murray, D.K. Granner, P.A. Mayes, and V.W. Rodwell, ed. McGraw-Hill Companies, Inc.
Bertics, S.J., R.R. Grummer, C. Cadorniga-Valino, and E.E. Stoddard. 1992. Effect of prepartum dry matter intake on liver triglyceride concentration and early lactation. J. Dairy Sci. Sci 75:1914–1922.
Bigner, D.R., J.P. Goff, M.A. Faust, J.L. Burton, H.D. Tyler, and R.L. Horst. 1996. Acidosis effects on insulin response during glucose tolerance tests in Jersey cows. J Dairy Sci. 79:2182-2188.
Block, E. 1984. Manipulating dietary anions and cations for prepartum dairy cows to reduce incidence of milk fever. J. Dairy Sci. 67:2939–2948.
Block, E. 2010. Transition cow research – what makes sense today?. Pages 75–98 in Proc. High Plains Dairy Conf. Amarillo, TX.
Boda, J.M., and H.H. Cole. 1956. Calcium metabolism with special reference to parturient paresis (milk fever) in dairy cattle: A review. J. Dairy Sci. 39:1027–1054.
Bouchard, R., and H.R. Conrad. 2003. Sulfur requirement of lactating dairy cows. I. Sulfur balance and dietary supplementation. J Dairy Sci 56:1276–1282.
Box, G., & Cox, D. 1964. An analysis of transformations. J Royal Statistical Society. Series B (Methodological), 26(2), 211-252.
Braithwaite, G.D. 1976. Calcium and phosphorus metabolism in ruminants with special reference to parturient paresis. J. Dairy Res. 43:501–520.
Breves, G., and B. Schröder. 1991. Comparative aspects of gastrointestinal phosphorus metabolism. Nutr. Res. Rev. 4:125–140.
Brini, M., and E. Carafoli. 2000. Calcium signalling: a historical account, recent developments and future perspectives. Cell. Mol. Life Sci. 57:354–370.
Brintrup, R., T. Mooren, U. Meyer, H. Spiekers, and E. Pfeffer. 1993. Effects of two levels of phosphorus intake on performance and faecal phosphorus excretion of dairy cows. J. Anim. Physiol. Anim. Nutr. (Berl). 69:29–36.
Brockman, R.P., and B. Laarveld. 1986. Hormonal regulation of metabolism in rumininants; a review. Livest. Prod. Sci. 14:313–334.
Bronner, F., D. Pansu, and W.D. Stein. 1986. Analysis of Calcium Transport in Rat Intestine. S.G. Massry, M. Olmer, and E. Ritz, ed. Springer US, Boston, MA.
129
Bronner, F. 1987. Intestinal calcium absorption: mechanisms and applications. J. Nutr. 117:1347–1352.
Brown, E.M. 2007. Clinical lessons from the calcium-sensing receptor. Nat. Clin. Pract. Endocrinol. Metab. 3:122–133.
Brüngger, M., H.N. Hulter, and R. Krapf. 1997. Effect of chronic metabolic acidosis on the growth hormone/IGF-1 endocrine axis: New cause of growth hormone insensitivity in humans. Kidney Int. 51:216–221.
Capuco, A. V., R.M. Akers, and J.J. Smith. 1997. Mammary growth in Holstein cows during the dry period: quantification of nucleic acids and histology. J. Dairy Sci. 80:477-487.
Care, A.D., R.C. Brown, A.R. Farrar, and D.W. Pickard. 1984. Magnesium absorption from the rumen of sheep. J. Exp. Physiol. 69:577–587.
Challa, A., W. Chan, R.J. Krieg, M.A. Thabet, F. Liu, R.L. Hintz, and J.C. Chan. 1993a. Effect of metabolic acidosis on the expression of insulin-like growth factor and growth hormone receptor. Kidney Int. 44:1224-1227.
Challa, A., R.J. Krieg, M.A. Thabet, J.D. Veldhuis, and J.C. Chan. 1993b. Metabolic acidosis inhibits growth hormone secretion in rats: mechanism of growth retardation. Am. J. Physiol. 265:E547-E553.
Chapinal, N., M. Carson, T.F. Duffield, M. Capel, S. Godden, M. Overton, J.E.P. Santos, and S.J. LeBlanc. 2011. The association of serum metabolites with clinical disease during the transition period. J. Dairy Sci. 94:4897–4903.
Charbonneau, E., D. Pellerin, and G.R. Oetzel. 2006. Impact of lowering dietary cation-anion difference in nonlactating dairy cows: A meta-analysis. J. Dairy Sci. 89:537–548.
Chew, B.P., R.E. Erb, J. Fessler, C.J. Callahan, and P. V. Malven. 1979. Effects of ovariectomy during pregnancy and of prematurely induced parturition on progesterone, estrogens, and calving traits. J. Dairy Sci. 62:557–566.
Christakos, S. 2012. Recent advances in our understanding of 1,25-dihydroxyvitamin D3 regulation of intestinal calcium absorption. Arch. Biochem. Biophys. 523:73–76.
Clapham, D.E. 1995. Calcium signaling. Cell 80:259–268.
Constable, P.D. 1999. Clinical assessment of acid-base status. Vet. Clin. North Am. Food Anim. Pract. 15:447–471.
Constable, P.D. 2014. Acid-base assessment: When and how to apply the henderson-hasselbalch equation and strong ion difference theory. Vet. Clin. North Am. - Food Anim. Pract. 30:295–316.
130
Contreras, G.A., and L. Sordillo. 2011. Lipid mobilization and inflammatory responses during the transition period of dairy cows. Comp. Immunol. Microbiol. Infect. Dis. 34:281–289.
Contreras, G.A., C. Strieder-Barboza, and W. Raphael. 2017. Adipose tissue lipolysis and remodeling during the transition period of dairy cows. J. Anim. Sci. Biotechnol. 8:41-52.
Coppock, C.E., P.A. Grant, S.J. Portzer, D.A. Charles, and A. Escobosa. 1982. Lactating dairy cow responses to dietary sodium, chloride, and bicarbonate during hot weather. J. Dairy Sci. 65:566–576.
Coppock, C.E., R.W. Everett, R.P. Natzke, and H.R. Ainslie. 1974. Effect of dry period length on Holstein milk production and selected disorders at parturition. J. Dairy Sci. 57:712–718.
Costanzo, L.S., and E.E. Windhager. 1978. Calcium and sodium transport by the distal convoluted tubule of the rat. Am. J. Physiol. 235:F492–F506.
Curtis, C.R., H.N. Erb, C.J. Sniffen, and R.D. Smith. 1984. Epidemiology of parturient paresis: Predisposing factors with emphasis on dry cow feeding and management. J. Dairy Sci. 67:817–825.
Curtis, C.R., H.N. Erb, C.J. Sniffen, R.D. Smith, and D.S. Kronfeld. 1985. Path analysis of dry period nutrition, postpartum metabolic and reproductive disorders, and mastitis in Holstein cows. J. Dairy Sci. 68:2347–2360.
de Carvalho, P.R., M.C.G. Pita, J.E. Loureiro, H.R. Tanaka, and J.C.S. Ribeiro. 2010. Manganese deficiency in bovines: Connection between manganese metalloenzyme dependent in gestation and congenital defects in newborn calves. Pakistan J. Nutr. 9:488–503.
De Koster, J.D., and G. Opsomer. 2013. Insulin resistance in dairy cows. Vet. Clin. North Am. - Food Anim. Pract. 29:299–322.
DeGaris, P.J., and I.J. Lean. 2008. Milk fever in dairy cows: A review of pathophysiology and control principles. Vet. J. 176:58–69.
Dennis, V.W. 1996. Phosphate metabolism: Contribution of different cellular compartments. Kidney Int. 49:938–942.
Diernaes, L., J. Sehested, P.D. Moller, and E. Skadhauge. 1994. Sodium and chloride transport across the rumen epithelium of cattle in vitro: effect of short-chain fatty acids and amiloride. Exp. Physiol. 79:755–762.
Doepel, L., H. Lapierre, and J.J. Kennelly. 2002. Peripartum performance and metabolism of dairy cows in response to prepartum energy and protein intake. J. Dairy Sci. 85:2315–2334.
131
Drackley, J.K. 1999. Biology of dairy cows during the transition period: The final frontier?. J. Dairy Sci. 82:2259–2273.
Ebashi, S. 1985. Ca2+ in biological systems. Experientia 41:978–981.
Ebashi, S., and M. Endo. 1968. Calcium ion and muscle contraction. Prog. Biophys. Mol. Biol. 18:123–183.
Elanco Animal Health. 2009. The 5-point body condition scoring system. Bulletin AI 10752. Elanco Animal Health, Greenfield, IN.
Eley, R.M., W.W. Thatcher, F.W. Bazer, C.J. Wilcox, R.B. Becker, H.H. Head, and R.W. Adkinson. 1978. Development of the conceptus in the bovine. J. Dairy Sci. 61:467–473.
Emery, R., J. Liesman, and T. Herdt. 1992. Metabolism of long chain fatty acids by ruminant liver. J. Nutr. 122:850–854.
Ender, F., I. Dishington, and A. Helgebostad. 1971. Calcium balance studies in dairy cows under experimental induction and prevention of hypocalcaemic paresis puerperalis. Tierphysiol., Tierernahrg. U. Futtermittelkde. 28:233–256.
Erdman, R.A. 1988. Dietary buffering requirements of the lactating dairy cow: a review. J. Dairy Sci. 71:3246–3266.
Evans, H.J., and G.J. Sorger. 1966. Role of mineral elements with emphasis on the univalent cations. Annu. Rev. Plant Physiol. 17:47–76.
Favus, M., and D. Goltzman. 2013. Regulation of calcium and magnesium. Pages 173-179 in Primer on the Metabolic Bone Diseases and Disoreders of Mineral Metabolism. 8th Edition. C.J. Rosen, ed. John Wiley & Sons, Inc.
Faylon, M.P., D.E. Koltes, and D.M. Spurlock. 2014. Regulation of lipid droplet-associated proteins following growth hormone administration and feed restriction in lactating Holstein cows. J. Dairy Sci. 97:2847–55.
Feher, J.J. 1984. Measurement of facilitated calcium diffusion by a soluble calcium-binding protein. Biochim. Biophys. Acta 773:91–98.
Ferguson, J. D., D.T. Galligan, and N. Thomsen. 1994. Principal descriptors of body condition score in Holstein cows. J. Dairy Sci. 77:2695–2703.
Fernando, S.C., H.T. Purvis, F.Z. Najar, L.O. Sukharnikov, C.R. Krehbiel, T.G. Nagaraja, B.A. Roe, and U. De Silva. 2010. Rumen microbial population dynamics during adaptation to a high-grain diet. Appl. Environ. Microbiol. 76:7482–7490.
132
Fleet, J.C., and R.D. Schoch. 2010. Molecular mechanisms for regulation of intestinal calcium absorption by vitamin D and other factors. Crit. Rev. Clin. Lab. Sci. 47:181–195.
Formigoni, A., and E. Trevisi. 2003. Transition cow: Interaction with fertility. Vet. Res. Commun. 27:143–152.
Fraser, D., and E. Kodicek. 1970. Unique biosynthesis by kidney of a biologically active vitamin D metabolite. Nature 228:764–766.
Friedman, P., and F. Gesek. 1995. Cellular calcium transport in renal epithelia: Measurement, mechanisms, and regulation. Physiol. Rev. 75:429–471.
Gaebel, G., H. Martens, M. Suendermann, and P. Galfi. 1987. The effect of diet, intraruminal pH and osmolarity on sodium, chloride and magnesium absorption from the temporarily isolated and washed reticulo-rumen of sheep. Q. J. Exp. Physiol. 72:501–511.
Garton, G.A. 1969. Digestion and absorption of lipids in the ruminant. Symp. Proc. Lipid Dig. Rumen 7:131–139.
Gearhart, M.A., C.R. Curtis, H.N. Erb, R.D. Smith, C.J. Sniffen, L.E. Chase, and M.D. Cooper. 1990. Relationship of changes in condition score to cow health in Holsteins. J. Dairy Sci. 73:3132–3140.
Gochman, N., and J. M. Schmitz. 1972. Application of a new peroxide indicator reaction to the specific, automated determination of glucose with glucose oxidase. Clin. Chem. 18:943-950.
Goff, J.P. 2006. Macromineral physiology and application to the feeding of the dairy cow for prevention of milk fever and other periparturient mineral disorders. Anim. Feed Sci. Technol. 126:237–257.
Goff, J.P. 2014. Calcium and magnesium disorders. Vet. Clin. North Am. - Food Anim. Pract. 30:359–381.
Goff, J.P. 2015a. Minerals. Pages 567-592. Dukes' Physiology of Domestic Animals. 13th Edition. W. O. Reece. ed. Wiley-Blackwell.
Goff, J.P. 2015b. Digestion and absorption of nutrients. Pages 502-521. Dukes' Physiology of Domestic Animals. 13th Edition. W. O. Reece. ed. Wiley-Blackwell.
Goff, J.P., A. Liesegang, and R.L. Horst. 2014. Diet-induced pseudohypoparathyroidism: A hypocalcemia and milk fever risk factor. J. Dairy Sci. 97:1520–1528.
Goff, J.P., and R.L. Horst. 1997. Physiological changes at parturition and their relationship to metabolic disorders. J. Dairy Sci. 80:1260–1268.
133
Goff, J.P., E.T. Littledike, and R.L. Horst. 1986. Effect of synthetic bovine parathyroid hormone in dairy cows: prevention of hypocalcemic parturient paresis. J. Dairy Sci. 69:2278–2289.
Goff, J.P., K. Kimura, and R.L. Horst. 2002. Effect of mastectomy on milk fever, energy, and vitamins A, E, and beta-carotene status at parturition. J. Dairy Sci. 85:1427–1436.
Goff, J.P., R.L. Horst, F.J. Mueller, J.K. Miller, G.A. Kiess, and H.H. Dowlen. 1991. Addition of chloride to a prepartal diet high in cations increases 1,25-dihydroxyvitamin D response to hypocalcemia preventing milk fever. J. Dairy Sci. 74:3863–3871.
Grace, N.D., M.J. Ulyatt, and J.C. Macrae. 1974. Quantitative digestion of fresh herbage by sheep: III. The movement of Mg, Ca, P, K and Na in the digestive tract. J. Agric. Sci. 82:321–330.
Grafton, G., and L. Thwaite. 2001. Calcium channels in lymphocytes. Immunology 104:119–126.
Grant, R.J., and J.L. Albright. 1995. Behavior and management transition period in dairy. J. Anim. Sci. 73:2791–2803.
Green, H.B., R.L. Horst, D.C. Beitz, and E.T. Littledike. 1981. Vitamin D metabolites in plasma of cows fed a prepartum low-calcium diet for prevention of parturient hypocalcemia. J. Dairy Sci. 64:217–226.
Greenfield, R.B., M.J. Cecava, and S.S. Donkin. 2000. Changes in mRNA expression for gluconeogenic enzymes in liver of dairy cattle during the transition to lactation. J. Dairy Sci. 83:1228–1236.
Gröhn, Y.T., S.W. Eicker, V. Ducrocq, and J.A. Hertl. 1998. Effect of diseases on the culling of Holstein dairy cows in New York state. J. Dairy Sci. 81:966–978.
Grummer, R.R. 1995. Impact of changes in organic nutrient metabolism on feeding the transition dairy cow J. Anim. Sci. 73:2820–2833.
Grünberg, W., S.S. Donkin, and P.D. Constable. 2011. Periparturient effects of feeding a low dietary cation-anion difference diet on acid-base, calcium, and phosphorus homeostasis and on intravenous glucose tolerance test in high-producing dairy cows. J. Dairy Sci. 94:727–745.
Gulay, M.S., M.J. Hayen, K.C. Bachman, T. Belloso, M. Liboni, and H.H. Head. 2003. Milk production and feed intake of Holstein cows given short (30-d) or normal (60-d) dry periods. J. Dairy Sci. 86:2030–2038.
134
Ha, N., C. Drögemüller, C. Reimer, R.M. Bruckmaier, H. Simianer, and J.J. Gross. 2017. Liver transcriptome analysis reveals important factors involved in the metabolic adaptation of the transition cow. J. Dairy Sci. 100:1–13.
Hansard, S.L., C.L. Comar, and M.P. Plumlee. 1954. The effects of age upon calcium utilization and maintenance requirements in the bovine. J. Anim. Sci. 13:25-36.
Hargreaves, M., D. Angus, K. Howlett, N.M. Conus, and M. Febbraio. 1996. Effect of heat stress on glucose kinetics during exercise. J. Appl. Physiol. 81:1594–1597.
Hartwig, A. 2001. Role of magnesium in genomic stability. Micronutr. Genomic Stab. 475:113–121.
Hayirli, A. 2006. The role of exogenous insulin in the complex of hepatic lipidosis and ketosis associated with insulin resistance phenomenon in postpartum dairy cattle. Vet. Res. Commun. 30:749–774.
Hayirli, A., R.R. Grummer, E. V. Nordheim, and P.M. Crump. 2002. Animal and dietary factors affecting feed intake during the prefresh transition period in Holsteins. J. Dairy Sci. 85:3430–3443.
Herdt, T.H. 1988. Fuel homeostasis in the ruminant. Vet. Clin. North Am. Food Anim. Pract. 4:213–231.
Herdt, T.H., T. Wensing, H.P. Haagsman, L.M.G. van Golde, and J. Breukink. 1988. Hepatic triacylglycerol synthesis during a period of fatty liver development in sheep. J. Anim. Sci. 66:1997–2013.
Hers, H.G., and L. Hue. 1983. Gluconeogenesis and related aspects of glycolysis. Annu. Rev. Biochem. 52:617–653.
Hidaka, H., T. Yamaki, M. Naka, T. Tanaka, H. Hayashi, and R. Kobayashi. 1980. Calcium-regulated smooth muscle modulator protein interacting agents inhibit protein kinase and ATPase. Mol. Pharmacol. 17:66–72.
Holick, M. 2008. Sunlight, UV-radiation, vitamin D and skin cancer: How much sunlight do we need? Pages 1-15 in Sunlight, Vitamin D and Skin Cancer. Advances in Experimental Medicine and Biology. vol 624. N. Black, I. R. Cohen, A. Lajtha, J. D. Lambris, R. Paoletti. Ed. Reichrath J. Landes Bioscience.
Holt, C. 1981. Some principles determining salt composition and partitioning of ions in milk. J. Dairy Sci. 64:1958–1964.
Holtenius, K., S. Agenäs, C. Delavaud, and Y. Chilliard. 2003. Effects of feeding intensity during the dry period. 2. Metabolic and hormonal responses. J. Dairy Sci. 86:883–891.
135
Hopfer, U., and C.M. Liedtke. 1987. Proton and bicarbonate transport mechanisms in the intestine. Annu. Rev. Physiol. 49:51–67.
Horst, R.L. 1986. Regulation of calcium and phosphorus homeostasis in the dairy cow. J. Dairy Sci. 69:604–616.
Horst, R.L., E.T. Littledike, J.L. Riley, and J.L. Napoli. 1981. Quantitation of vitamin D and its metabolites and their plasma concentrations in five species of animals. Anal. Biochem. 116:189–203.
Horst, R.L., J.P. Goff, and T.A. Reinhardt. 1990. Advancing age results in reduction of intestinal and bone 1,25-dihydroxyvitamin D receptor. Endocrinology 126:1053–1057.
Horst, R.L., J.P. Goff, and T.A. Reinhardt. 1994. Calcium and vitamin D metabolism in the dairy cow. J. Dairy Sci. 77:1936–1951.
Horst, R.L., J.P. Goff, and T.A. Reinhardt. 2005. Adapting to the transition between gestation and lactation: Differences between rat, human and dairy cow. J. Mammary Gland Biol. Neoplasia 10:141–156.
Horst, R.L., J.P. Goff, T.A. Reinhardt, and D.R. Buxton. 1997. Strategies for preventing milk fever in dairy cattle. J. Dairy Sci. 80:1269–1280.
Horsting, M., and H.F. DeLuca. 1969. In vitro production of 25-hydroxycholecalciferol. Biochem. Biophys. Res. Commun. 36:251–256.
House, W.A., and A.W. Bell. 1993. Mineral accretion in the fetus and adnexa during late gestation in Holstein cows. J. Dairy Sci. 76:2999–3010.
Hu, W., and M.R. Murphy. 2004. Dietary cation-anion difference effects on performance and acid-base status of lactating dairy cows: a meta-analysis. J. Dairy Sci. 87:2222–2229.
Huntington, G.B. 1984. Net absorption of glucose and nitrogenous compounds by lactating Holstein cows. J. Dairy Sci. 67:1919–1927.
Hunziker, W., M.R. Walters, J.E. Bishop, and A.W. Norman. 1982. Effect of vitamin D status on the equilibrium between occupied and unoccupied 1,25-diydroxyvitamin D intestinal receptors in the chick. J. Clin. Invest. 69:826–834.
Hurley, W.L. 1989. Mammary gland function during involution. J. Dairy Sci. 72:1637–1646.
Ingvartsen, K.L., and K. Moyes. 2013. Nutrition, immune function and health of dairy cattle. Anim. Consort. 7:112–122.
136
Ingvartsen, K.L., R.J. Dewhurst, and N.C. Friggens. 2003. On the relationship between lactational performance and health: Is it yield or metabolic imbalance that cause production diseases in dairy cattle? A position paper. Livest. Prod. Sci. 83:277–308.
Jaiswal, J.K. 2001. Calcium – how and why? J. Biosci. 26:357–363.
Janovick, N.A., and J.K. Drackley. 2010. Prepartum dietary management of energy intake affects postpartum intake and lactation performance by primiparous and multiparous Holstein cows. J Dairy Sci 93:3086–3102.
Janovick, N.A., Y.R. Boisclair, and J.K. Drackley. 2011. Prepartum dietary energy intake affects metabolism and health during the periparturient period in primiparous and multiparous Holstein cows. J. Dairy Sci. 94:1385–1400.
Jardon, P.W. 1995. Using urine pH to monitor anionic salt programs. Compend. Contin. Educ. Pract. Vet. 17:860–862.
Jarrett, I.G., O.H. Filsell, and F.J. Ballard. 1976. Utilization of oxidizable substrates by the sheep hind limb: Effects of starvation and exercise. Metabolism 25:523–531.
Johnson, M.M., and J.P. Peters. 1993. Technical note: an improved method to quantify nonesterified fatty acids in bovine plasma. J. Anim. Sci. 71:753–756.
Jørgensen, E., and A.R. Pedersen. 1998. How to obtain those nasty standard errors from transformed data – and why they should not be used. Biometry Research Unit - Internal report 7. Danish Institute of Agricultural Sciences. pp 20.
Kaplan, J.H. 2002. Biochemistry of Na,K-ATPase. Annu. Rev. Biochem. 71:511–535.
Kehrli, M.E., B.J. Nonnecke, and J.A. Roth. 1989. Alterations in bovine neutrophil function during the periparturient period. Am. J. Vet. Res. 50:207–214.
Kimura, K., T.A. Reinhardt, and J.P. Goff. 2006. Parturition and hypocalcemia blunts calcium signals in immune cells of dairy cattle. J. Dairy Sci. 89:2588–2595.
Kinder, B.K., and A.F. Stewart. 2002. Hypercalcemia. Curr. Probl. Surg. 39:360–447.
Ko, Y.H., M. Bianchet, L.M. Amzel, and P.L. Pedersen. 1997. Novel insights into the chemical mechanism of ATP synthase. J. Biol. Chem. 272:18875–18881.
Ko, Y.H., S. Hong, and P.L. Pedersen. 1999. Chemical mechanism of ATP synthase. J. Biol. Chem. 274:28853–28856.
Koltes, D.A., and D.M. Spurlock. 2011. Coordination of lipid droplet-associated proteins during the transition period of Holstein dairy cows. J. Dairy Sci. 94:1839–1848.
137
Komiscarczuk, S., R.J. Merry, and A.B. McAllan. 1987. Effect of different levels of phosphorus on rumen microbial fermentation and synthesis determined using a continuous culture technique. Br. J. Nutr. 57:279–290.
Kossaibati, M.A., and R.J. Esslemont. 1997. The costs of production diseases in dairy herds in England. Vet. J. 154:41–51.
Krebs, H.A. 1966. The regulation of the release of ketone bodies by the liver. Adv. Enzyme Regul. 4:339–353.
Krueger, B.K., J. Forn, and P. Greengard. 1977. Depolarization-induced phosphorylation of specific proteins, mediated by calcium-ion influx, in rat-brain synaptosomes. J. Biol. Chem. 252:2764–2773.
Kunz, P.L., J.W. Blum, I.C. Hart, H. Bickel, and J. Landis. 1985. Effects of different energy intakes before and after calving on food intake, performance and blood hormones and metabolites in dairy cows. Anim. Prod. 40:219–231.
Langin, D., A. Dicker, G. Tavernier, J. Hoffstedt, A. Mairal, M. Rydén, E. Arner, A. Sicard, C.M. Jenkins, N. Viguerie, V. Van Harmelen, R.W. Gross, C. Holm, and P. Arner. 2005. Adipocyte lipases and defect of lipolysis in human obesity. Diabetes 54:3190–3197.
Larsen, M., and N.B. Kristensen. 2009. Effect of abomasal glucose infusion on splanchnic amino acid metabolism in periparturient dairy cows. J. Dairy Sci. 92:3306–3318.
Larsen, T., G. Moller, and R. Bellio. 2001. Evaluation of clinical and clinical chemical parameters in periparturient cows. J. Dairy Sci. 84:1749–1758.
Laster, D.B., and R.L. Prior. 1979. Development of the bovine fetus 6:1546–1553.
Lean, I.J., P.J. DeGaris, A.R. Rabiee, and E. Block. 2006. Hypocalcemia in dairy cows: Meta-analysis and dietary cation anion difference theory revisited. J. Dairy Sci. 89:669–684.
LeBlanc, S.J. 2010. Monitoring metabolic health of dairy cattle in the transition period. J. Reprod. Dev. 56 Suppl:S29-S35.
LeBlanc, S.J., K.E. Leslie, and T.F. Duffield. 2005. Metabolic predictors of displaced abomasum in dairy cattle. J. Dairy Sci. 88:159–170.
Leury, B.J., A.R. Bird, K.D. Chandler, and A.W. Bell. 1990. Glucose partitioning in the pregnant ewe: effects of undernutrition and exercise. Br. J. Nutr. 64:449–462.
Lewis, R.S. 2001. Calcium signaling mechanisms in T lymphocytes. Ann. Rev. Immunol. 19:497–521.
138
Littledike, E.T. 1976. Relationship of milk secretion to hypocalcemia in the dairy cow. J. Dairy Sci. 59:1947–1953.
Lomax, M.A., and G.D. Baird. 1983. Blood flow and nutrient exchange across the liver and gut of the dairy cow. Br. J. Nutr. 49:481–496.
Lovelock, J.E., and B.M. Porterfield. 1952. Blood clotting; the function of electrolytes and of calcium. Biochem. J. 50:415–420.
Malhorta, V.K. 2012. Water and mineral metabolism. Pages 292-305. In Biochemestry for Students. 12th Edition. Ed. Jaypee Brothers Medical Publishers.
Mann, S., F.A.L. Yepes, T.R. Overton, J.J. Wakshlag, A.L. Lock, C.M. Ryan, and D. V. Nydam. 2015. Dry period plane of energy: Effects on feed intake, energy balance, milk production, and composition in transition dairy cows. J. Dairy Sci. 98:3366–3382.
Mannstadt, M., H. Juppner, and T.J. Gardella. 1999. Receptors for PTH and PTHrP: their biological importance and functional properties. Am. J. Physiol. 277:F665–F675.
Manston, R. 1967. The influence of dietary calcium and phosphorus concentration on their absorption in the cow. Cambridge J. Agric. Sci. 68:263–268.
Martens, H., and G. Gabel. 1988. Transport of Na and Cl across the epithelium of ruminant forestomachs: Rumen and omasum. A review. Comp. Biochem. Physiol. - Part A Physiol. 90:569–575.
Martens, H., and I. Blume. 1987. Studies on the absorption of sodium and chloride from the rumen of sheep. Comp. Biochem. Physiol. - Part A Physiol. 86:653–656.
Martens, H., and M. Schweigel. 2000. Pathophysiology of grass tetany and other hypomagnesemia: implications for clinical management. Pages 339-368. In Digestive Physiology and Metabolism in Ruminants. Vol. 16. Elsevier Masson SAS.
Martens, H., and Y. Rayssiguier. 1980. Magnesium Metabolism and Hypomagnesaemia. Pages 447-466 in Digestive Physiology and Metabolism in Ruminants. Y. Ruckebush. ed. MTP press Limited.
Martinez, N., C.A. Risco, F.S. Lima, R.S. Bisinotto, L.F. Greco, E.S. Ribeiro, F. Maunsell, K. Galvão, and J.E.P. Santos. 2012. Evaluation of peripartal calcium status, energetic profile, and neutrophil function in dairy cows at low or high risk of developing uterine disease. J. Dairy Sci. 95:7158–7172.
139
Martinez, N., L.D.P. Sinedino, R.S. Bisinotto, E.S. Ribeiro, G.C. Gomes, F.S. Lima, L.F. Greco, C.A. Risco, K.N. Galvão, D. Taylor-Rodriguez, J.P. Driver, W.W. Thatcher, and J.E.P. Santos. 2014. Effect of induced subclinical hypocalcemia on physiological responses and neutrophil function in dairy cows. J. Dairy Sci. 97:874–887.
Martinez, N., L.D.P. Sinedino, R.S. Bisinotto, R. Daetz, C.A. Risco, K.N. Galvão, W.W. Thatcher, and J.E.P. Santos. 2016. Effects of oral calcium supplementation on productive and reproductive performance in Holstein cows. J. Dairy Sci. 99:8397–8416.
Martinez, N., R.M. Rodney, E. Block, L.L. Hernandez, C.D. Nelson, I.J. Lean, and J.E.P. Santos. 2018a. Effects of prepartum dietary cation-anion difference and source of vitamin D in dairy cows: Lactation performance and energy metabolism. J. Dairy Sci. 101: in press https://doi.org/10.3168/jds.2017-13739.
Martinez, N., R.M. Rodney, E. Block, L.L. Hernandez, C.D. Nelson, I.J. Lean, and J.E.P. Santos. 2018b. Effects of prepartum dietary cation-anion difference and source of vitamin D in dairy cows: Health and reproductive responses. J. Dairy Sci. 101: in press https://doi.org/10.3168/jds.2017-13740.
Martins, C.M., M.A. Arcari, K.C. Welter, A.S. Netto, C.A. Oliveira, and M. V. Santos. 2015. Effect of dietary cation-anion difference on performance of lactating dairy cows and stability of milk proteins. J Dairy Sci 98:2650–2661.
Martz, F.A., A.T. Belo, M.F. Weiss, R.L. Belyea, and J.P. Goff. 1990. True absorption of calcium and phosphorus from alfalfa and corn silage when fed to lactating cows. J. Dairy Sci. 73:1288–1295.
Massip, A. 1980. Relationship between pH, plasma cortisol and glucose concentrations in the calf at birth.. Br. Vet. J. 136:597–601.
Mayes, P.A., and D.A. Bender. 2003. Gluconeogenesis and control of the blood glucose. Pages 153-163. In Harper’ s Illustrated Biochemistry. 26th edition. R. K. Murray, D. K. Granner, P. A. Mayes and V. W. Rodwell. Ed. McGraw-Hill.
McDonald, P., R.A. Edwards, J.F.D. Greenhalgh, C.A. Morgan, L.A. Sinclair, and R.G. Wilkinson. 2011. Pages 103-137. In Animal nutrition. P. McDonald, R.A. Edwards, J.F.D. Greenhalgh, C.A. Morgan, L.A. Sinclair, and R.G. Wilkinson. 7th edition. Minerals. Ed. Prentice Hall.
McGrath, B.A., P.F. Fox, P.L.H. McSweeney, and A.L. Kelly. 2016. Composition and properties of bovine colostrum: a review. Dairy Sci. Technol. 96:133–158.
McNamara, J.P. 1991. Regulation of adipose tissue metabolism in support of lactation. J. Dairy Sci. 74:706–719.
140
Moore, S.J., M.J. VandeHaar, B.K. Sharma, T.E. Pilbeam, D.K. Beede, H.F. Bucholtz, J.S. Liesman, R.L. Horst, and J.P. Goff. 2000. Effects of altering dietary cation-anion difference on calcium and energy metabolism in peripartum cows. J. Dairy Sci. 83:2095–2104.
Morse, D., H.H. Head, C.J. Wilcox, H.H. van Horn, C.D. Hissem, and B. Harris. 1992. Effects of concentration of dietary phosphorus on amount and route of excretion. J. Dairy Sci. 75:3039–3049.
Mulligan, F.J., and M.L. Doherty. 2008. Production diseases of the transition cow. Vet. J. 176:3–9.
Mundy, G.R., and T.A. Guise. 1999. Hormonal control of calcium homeostasis. Clin. Chem. 45:1347–1352.
Neville, M.C., and C.D. Watters. 1983. Secretion of calcium into milk: Review.. J. Dairy Sci. 66:371–380.
Nordin, B.E.C. 1998. Calcium in health and disease. Cell Calcium 24:233–237.
Norman, H.D., J.R. Wright, and R.H. Miller. 2011. Potential consequences of selection to change gestation length on performance of Holstein cows.. J. Dairy Sci. 94:1005–1010.
NRC. 2001. Nutrient requirements of dairy cattle. 7th rev. ed. Natl. Acad. Press, Washington, DC.
Odom, T.W., P.C. Harrison, and W.G. Bottje. 1986. Effects of thermal-induced respiratory alkalosis on blood ionized calcium levels in the domestic hen. Poult. Sci. 65:570–573.
Oetzel, G.R. 1988. Parturient paresis and hypocalcemia in ruminant livestock. Vet. Clin. North Am. Anim. Pract. 4:351–364.
Oetzel, G.R. 2013. Oral calcium supplementation in peripartum dairy cows. Vet. Clin. North Am. - Food Anim. Pract. 29:447-455.
Oetzel, G.R., M.J. Fettman, D.W. Hamar, and J.D. Olson. 1991. Screening of anionic salts for palatability, effects on acid-base status, and urinary calcium excretion in dairy cows. J. Dairy Sci. 74:965–971.
Oh, M. 2000. New perspectives on acid-base balance. Semin. Dial. 13:212–219.
Oikawa, S., and G.R. Oetzel. 2006. Decreased insulin response in dairy cows following a four-day fast to induce hepatic lipidosis. J. Dairy Sci. 89:2999–3005.
Oliver, S.P., and L.M. Sordillo. 1988. Udder health in the periparturient period. J. Dairy Sci. 71:2584-2606.
141
Ospina, P.A., D. V. Nydam, T. Stokol, and T.R. Overton. 2010. Evaluation of nonesterified fatty acids and β-hydroxybutyrate in transition dairy cattle in the northeastern United States: Critical thresholds for prediction of clinical diseases. J. Dairy Sci. 93:546–554.
Overton, T.R., and M.R. Waldron. 2004. Nutritional management of transition dairy cows: strategies to optimize metabolic health. J. Dairy Sci. 87:E105–E119.
Peacock, M. 2010. Calcium metabolism in health and disease. Clin. J. Am. Soc. Nephrol. 5:23–30.
Pehrson, B., C. Svensson, I. Gruvaeus, and M. Virkki. 1999. The influence of acidic diets on the acid-base balance of dry cows and the effect of fertilization on the mineral content of grass. J. Dairy Sci. 82:1310–1316.
Phillips, C.J.C., and M.I. Rind. 2001. The effects on production and behavior of mixing uniparous and multiparous cows. J. Dairy Sci. 84:2424–2429.
Pilkis, S.J., and D.K. Granner. 1992. Molecular physiology of the regulation of hepatic gluconeogenesis and glycolysis. Annu. Rev Physiol. 54:885–909.
Power, M.L., R.P. Heaney, H.J. Kalkwarf, R.M. Pitkin, J.T. Repke, R.C. Tsang, and J. Schulkin. 1999. The role of calcium in health and disease. Am. J. Obstet. Gynecol. 181:1560–1569.
Quinlan, K., and M. DeSesa. 1955. Spectrophotometric determination of phosphorus as molybdiphosphoric acid. Anal. Chem. 20:749–751.
Quiroz Rocha, G., S.J. LeBlanc, T.F. Duffield, D. Wood, K.E. Leslie, and R.M. Jacobs. 2009. Reference limits for biochemical and hematological analytes of dairy cows one week before and one week after parturition. Can. Vet. J. 50:383–388.
Ramberg, C.F., G.P. Mayer, D.S. Kronfeld, J.M. Phang, and M. Berman. 1970. Calcium kinetics in cows during late pregnancy, parturition, and early lactation. Am J Physiol 219:1166–1177.
Rastani, R.R., R.R. Grummer, S.J. Bertics, A. Gümen, M.C. Wiltbank, D.G. Mashek, and M.C. Schwab. 2005. Reducing dry period length to simplify feeding transition cows: milk production, energy balance, and metabolic profiles. J. Dairy Sci. 88:1004–1014.
Razzaghi, A., H. Aliarabi, M.M. Tabatabaei, A.A. Saki, R. Valizadeh, and P. Zamani. 2012. Effect of dietary cation-anion difference during prepartum and postpartum periods on performance, blood and urine minerals status of Holstein dairy cow. Asian-Australasian J. Anim. Sci. 25:486–495.
Reinhardt, T.A., J.D. Lippolis, B.J. McCluskey, J.P. Goff, and R.L. Horst. 2011. Prevalence of subclinical hypocalcemia in dairy herds. Vet. J. 188:122–124.
142
Reinhardt, T.A., R.L. Horst, and J.P. Goff. 1988. Calcium, phosphorus, and magnesium homeostasis in ruminants. Vet. Clin. North Am. Food Anim. Pract. 4:331–350.
Remer, T. 2000. Influence of diet on acid-base balance. Semin Dial 13:221–226.
Reynolds, C.K., P.C. Aikman, B. Lupoli, D.J. Humphries, and D.E. Beever. 2003. Splanchnic metabolism of dairy cows during the transition from late gestation through early lactation. J. Dairy Sci. 86:1201–1217.
Reynolds, L.P., C.L. Ferrell, D.A. Robertson, and S.P. Ford. 1986. Metabolism of the gravid uterus, foetus and uter-placenta at several stages of gestation in cows. J. Agric. Sci. 106:437-444.
Ribeiro, E.S., F.S. Lima, L.F. Greco, R.S. Bisinotto, A.P.A. Monteiro, M. Favoreto, H. Ayres, R.S. Marsola, N. Martinez, W.W. Thatcher, and J.E.P. Santos. 2013. Prevalence of periparturient diseases and effects on fertility of seasonally calving grazing dairy cows supplemented with concentrates. J. Dairy Sci. 96:1–16.
Ribeiro, E.S., G. Gomes, L.F. Greco, R.L.A. Cerri, A. Vieira-Neto, P.L.J. Monteiro Jr., F.S. Lima, R.S. Bisinotto, W.W. Thatcher, and J.E.P. Santos. 2016. Carryover effect of postpartum inflammatory diseases on developmental biology and fertility in lactating dairy cows. J. Dairy Sci. 99:2201-2220.
Riond, J. 2001. Animal nutrition and acid-base balance. Eur. J. Nutr. 40:245–254.
Rizza, R.A., L.J. Mandarino, and J.E. Gerich. 1982. Cortisol-induced insulin resistance in man: Impaired suppression of glucose production and stimulation of glucose utilization due to a postreceptor defect of insulin action. J. Clin. Endocrinol. Metab. 54:173–176.
Roberts, T., N. Chapinal, S.J. Leblanc, D.F. Kelton, J. Dubuc, and T.F. Duffield. 2012. Metabolic parameters in transition cows as indicators for early-lactation culling risk. J. Dairy Sci. 95:3057–3063.
Rodney, R.M., N. Martinez, E. Block, L. L. Hernandez, P. Celi, C. D. Nelson, J.E.P. Santos, and I.J. Lean. 2018. Effects of prepartum dietary cation-anion difference and source of vitamin D in dairy cows: Vitamin D, mineral, and bone metabolism. J. Dairy Sci. 101: https://doi.org/10.3168/jds.2017-13737.
Romani, A., and A. Scarpa. 1992. Regulation of cell magnesium. Arch. Biochem. Biophys. 298:1–12.
Rosol, T., and C.C. Capen. 1997. Calcium-regulating hormones and diseases of abnormal mineral (calcium, phosphorus, magnesium) metabolismolism. Pages 619-702. In Clinical Biochemistry of Domestic Animals. Fifth Edition. J.J. Kaneko, J.W. Harvey, and M.L. Bruss, ed. Academic Press.
143
Rosol, T., D.J. Chew, T.J. Rosoi, D.J. Chew, L.A. Nagode, and C.C. Capen. 1995. Pathophysiology of calcium metabolism Vet. Clin. Pathol. 24:49–63.
Rubin, R.P. 1970. Role of calcium in the release substances of neurotransmitter and hormones. Pharmacol. Rev. 22:389–428.
Sangild, P.T., M. Schmidt, H. Jacobsen, A.L. Fowden, A. Forhead, B. Avery, and T. Greve. 2000. Blood chemistry, nutrient metabolism, and organ weights in fetal and newborn calves derived from in vitro-produced bovine embryos. Biol. Reprod. 62:1495–1504.
Sano, H., S. Narahara, T. Kondo, A. Takahashi, and Y. Terashima. 1993. Insulin responsiveness to glucose and tissue responsiveness to insulin during lactation in dairy cows. Domest. Anim. Endocrinol. 10:191–197.
Santos, J.E.P., R.S. Bisinotto, E.S. Ribeiro, F.S. Lima, L.F. Greco, C.R. Staples, and W.W. Thatcher. 2010. Applying nutrition and physiology to improve reproduction in dairy cattle. Soc. Reprod. Fertil. Suppl. 67:387-403.
Santschi, D.E., D.M. Lefebvre, R.I. Cue, C.L. Girard, and D. Pellerin. 2011. Economic effect of short (35-d) compared with conventional (60-d) dry period management in commercial Canadian Holstein herds. J. Dairy Sci. 94:4734–4743.
Seifi, H.A., S.J. LeBlanc, K.E. Leslie, and T.F. Duffield. 2011. Metabolic predictors of post-partum disease and culling risk in dairy cattle. Vet. J. 188:216–220.
Shirazi-Beechey, S.P., J.I. Penny, J. Dyer, I.S. Wood, P.S. Tarpey, D. Scott, and W. Buchan. 1996. Epithelial phosphate transport in ruminants, mechanisms and regulation. Kidney Int. 49:992–996.
Siggaard-Andersen, O. 2006. Acid-base balance. Encycl. Respir. Med. Feb:5-10.
Silanikove, N., E. Maltz, A. Halevi, and D. Shinder. 1997. Metabolism of water, sodium, potassium, and chlorine by high yielding dairy cows at the onset of lactation. J. Dairy Sci. 80:949–956.
Silva, P.R., J.G. Moraes, L.G. Mendonça, A.A. Scanavez, G. Nakagawa, J. Fetrow, M.I. Endres, and R.C. Chebel. 2013. Effects of weekly regrouping of prepartum dairy cows on metabolic, health, reproductive, and productive parameters. J. Dairy Sci. 96:4436-4446.
Soetan, K.O., C.O. Olaiya, and O.E. Oyewole. 2010. The importance of mineral elements for humans, domestic animals and plants : A review. African J. Food Sci. 4:200–222.
Somlyo, A.P., A.J. Wasserman, T. Kitazawa, M. Bond, H. Shuman, and A. V. Somlyo. 1985. Calcium and sodium distribution and movements in smooth muscle. Experientia 41:981–988.
144
Souza, A.H., H. Ayres, R.M. Ferreira, and M.C. Wiltbank. 2008. A new presynchronization system (Double-Ovsynch) increases fertility at first postpartum timed AI in lactating dairy cows. Theriogenology 70:208–215.
Sørensen, J.T., and C. Enevoldsen. 1991. Effect of dry period length on milk production in subsequent lactation. J. Dairy Sci. 74:1277–1283.
Spanghero, M. 2004. Prediction of urinary and blood pH in non-lactating dairy cows fed anionic diets. Anim. Feed Sci. Technol. 116:83–92.
Staples, C.R., W.W. Thatcher, and J.H. Clark. 1990. Relationship between ovarian activity and energy status during the early postpartum period of high producing dairy cows. J. Dairy Sci. 73:938–947.
Stern, M.D., and W.H. Hoover. 1979. Methods for determining and factors affecting rumen microbial protein synthesis: A review. J. Anim. Sci. 49:1590–1603.
Stewart, P.A. 1983. Modern quantitative acid- base chemistry. Can. J. Physiol. Pharmacol. 61:1444–1461.
Stewart, T.A., K.T.D.S. Yapa, and G.R. Monteith. 2015. Altered calcium signaling in cancer cells. Biochim. Biophys. Acta 1848:2502–2511.
Stone, W.C., and S.A. Mosley. 2017. Nutritional diagnostic troubleshooting. Pages 771-786. In Large dairy herd management. 3rd ed. D. K. Beede. ADSA.
St-Pierre, N., and W.P. Weiss. 2017. Variability in feed sampling and analyses. Pages 713-722. In Large dairy herd management. 3rd ed. D. K. Beede. ADSA
Sukhija, P. S., and D. L. Palmquist. 1988. Rapid method for determination of total fatty acid content and composition of feedstuffs and feces. J. Agric. Food Chem. 36:1202–1206.
Suttle, N.F. 2010. Mineral Nutrition of Livestock, 4th Edition.
Swanson, E.W. 1965. Comparing continuous milking with sixty-day dry periods in successive lactations. J. Dairy Sci. 48:1205–1209.
Swanson, E.W., R.A. Monroe, D.B. Zilversmit, W.J. Visek, and C.L. Comar. 1956. A study of variations in secretion of Ca45 by the mammary glands of dairy cows. J. Dairy Sci. 39:1594–1608.
Tajima, K., R.I. Aminov, and T. Nagamine. 2001. Diet-dependent shifts in the bacterial population of the rumen revealed with real-time PCR. Appl. Environ. Microbiol. 67:2766–2774.
145
Talebi, A., M.A.G. von Keyserlingk, E. Telezhenko, and D.M. Weary. 2014. Reduced stocking density mitigates the negative effects of regrouping in dairy cattle. J. Dairy Sci. 97:1358–1363.
Termine, J.D., and A.S. Posner. 1967. Amorphous/crystalline interrelationships in bone mineral. Calcif. Tissue Res. 1:8–23.
Teti, A., and A. Zallone. 2009. Do osteocytes contribute to bone mineral homeostasis? Osteocytic osteolysis revisited. Bone 44:11–16.
Thatcher, W.W., C.J. Wilcox, R.J. Collier, D.S. Eley, and H. Head. 1980. Bovine conceptus – maternal interactions during the pre- and postpartum periods. J. Dairy Sci. 63:1530–1540.
Thilsing-Hansen, T., R.J. Jørgensen, and S. Østergaard. 2002. Milk fever control principles: A review. Acta Vet. Scand. 43:1–19.
Tomas, F.M., and B.J. Potter. 1976. The site of magnesium absorption from the ruminant stomach. Br. J. Nutr. 36:37–45.
Tucker, H.A. 2000. Hormones, Mammary Growth, and Lactation: a 41-Year Perspective. J. Dairy Sci. 83:874–884.
USDA. 2007. Dairy 2007. Part I: Reference of dairy cattle health and management practices in the United States. https://www.aphis.usda.gov/animal_health/nahms/dairy/downloads/dairy07/Dairy07_dr_PartI.pdf.
USDA. 2008. Dairy 2007, part III: reference of dairy cattle health and management practices in the United States. https://www.aphis.usda.gov/animal_health/nahms/dairy/downloads/dairy07/Dairy07_dr_PartIII_rev.pdf.
USDA. 2016. Dairy 2014, dairy cattle management practices in the United States. https://www.aphis.usda.gov/animal_health/nahms/dairy/downloads/dairy14/Dairy14_dr_PartI.pdf.
Vagnoni, D.B., and G.R. Oetzel. 1998. Effects of dietary cation-anion difference on the acid-base status of dry cows. J. Dairy Sci. 81:1643–1652.
Valadares, R. F. D., G. A. Broderick, S. C. Valadares Filho, and M. K. Clayton. 1999. Effect of replacing alfalfa silage with high moisture corn on ruminal protein synthesis estimated from excretion of total purine derivatives. J. Dairy Sci. 82:2686–2696.
Van De Graaf, S.F.J., I. Boullart, J.G.J. Hoenderop, and R.J.M. Bindels. 2004. Regulation of the epithelial Ca2+ channels TRPV5 and TRPV6 by 1α,25-
146
dihydroxy Vitamin D3 and dietary Ca2+. J. Steroid Biochem. Mol. Biol. 89–90:303–308.
van Saun, R.J., and C.J. Sniffen. 2014. Transition cow nutrition and feeding management for disease prevention. Vet. Clin. North Am. - Food Anim. Pract. 30:689–719.
Van Soest, P. J., J. B. Robertson, and B.A. Lewis. 1991. Methods for dietary fiber, neutral detergent fiber and nonstarch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74:3583–3597.
van’t Klooster, A.T. 1976. Adaptation of calcium absorption from the small intestine of dairy cows to changes in the dietary calcium intake and at the onset of lactation. Zeitschrift für Tierphysiologie Tierernährung und Futtermittelkd. 37:169–182.
Vandehaar, M.J., G. Yousif, B.K. Sharma, T.H. Herdt, R.S. Emery, M.S. Allen, and J.S. Liesman. 1999. Effect of energy and protein density of prepartum diets on fat and protein metabolism of dairy cattle in the periparturient period. J. Dairy Sci. 82:1282–1295.
Vazquez-Añon, M., S. Bertics, M. Luck, R.R. Grummer, and J. Pinheiro. 1994. Peripartum liver triglyceride and plasma metabolites in dairy cows. J. Dairy Sci. 77:1521–1528.
Vidal, B.C. Jr., K.D. Rausch, M.E. Tumbleson, and V. Singh. 2009. Determining corn germ and pericarp residual starch by acid hydrolysis. Cereal Chemistry 86:133-135.
Vieira-Neto, A., K.N. Galvão, W.W. Thatcher, and J.E.P. Santos. 2017a. Association among gestation length and health, production, and reproduction in Holstein cows and implications for their offspring. J. Dairy Sci. 100:3166–3181.
Vieira-Neto, A., I.R.P. Lima, F. Lopes, C. Lopera, R. Zimpel, L.D.P. Sinedino, K.C. Jeong, K. Galvão, W.W. Thatcher, C.D. Nelson, and J.E.P. Santos. 2017b. Use of calcitriol to maintain postpartum blood calcium and improve immune function in dairy cows. J. Dairy Sci. 100:5805–5823.
von Keyserlingk, M.A.G., D. Olenick, and D.M. Weary. 2008. Acute behavioral effects of regrouping dairy cows. J. Dairy Sci. 91:1011–1016.
Wang, C., and D.K. Beede. 1992. Effects of diets magnesium on acid-base status and calcium metabolism of dry cows fed acidogenic salts. J. Dairy Sci. 75:829–836.
Wang, S., E.H. Mcdonnell, F.A. Sedor, and J.G. Toffaletti. 2002. pH effects on measurements of ionized calcium and magnesium. Arch. Pathol. Lab. Med. 126:947–950.
147
Ward, G., L.H. Harbers, and J.J. Blaha. 1979. Calcium-containing crystals in alfalfa: their fate in cattle. J. Dairy Sci. 62:715–722.
Ward, G.M. 1966. Potassium metabolism of domestic ruminants—a review. J. Dairy Sci. 49:268–276.
Warner, C.I., and B.D. Stacy. 1972. Water, sodium and potassium movements across the rumen wall of sheep. Q. J. Exp. Physiol. 57:103–119.
Wasserman, R.H., and C.S. Fullmer. 1995. Vitamin D and intestinal calcium transport: Facts, speculations and hypotheses. J. Nutr. 15:1971–1979.
Wathes, D.C., M. Fenwick, Z. Cheng, N. Bourne, S. Llewellyn, D.G. Morris, D. Kenny, J. Murphy, and R. Fitzpatrick. 2007. Influence of negative energy balance on cyclicity and fertility in the high producing dairy cow. Theriogenology 68:232–241.
Weich, W., E. Block, and N.B. Litherland. 2013. Extended negative dietary cation-anion difference feeding does not negatively affect postpartum performance of multiparous dairy cows. J. Dairy Sci. 96:5780–5792.
Weiss, W.P. 2004. Macromineral digestion by lactating dairy cows: factors affecting digestibility of magnesium. J. Dairy Sci. 87:2167–2171.
Widrow, S.H., and N.G. Levinsky. 1962. The effect of parathyroid extract on renal tubular calcium reabsorption in the dog. J. Clin. Invest. 41:2151–2159.
Wilhelm, A.L., M.G. Maquivar, S. Bas, T.A. Brick, W.P. Weiss, H. Bothe, J.S. Velez, and G.M. Schuenemann. 1999. Effect of serum calcium status at calving on survival, health, and performance of postpartum Holstein cows and calves under certified organic management. Asian-Aus. J. Anim. Sci. 12:1111–1115.
Wilkens, M., C. Praechter, G. Breves, and B. Schroder. 2016. Stimulating effects of a diet negative in dietari cation-anion difference on calcium absorption from the rumen sheep. J. Anim. Physiol. Anim. Nutr. (Berl). 100:156–166.
Wu, Z., J.K. Bernard, K.P. Zanzalari, and J.D. Chapman. 2014. Effect of feeding a negative dietary cation-anion difference diet for an extended time prepartum on postpartum serum and urine metabolites and performance. J. Dairy Sci. 97:7133–7143.
Wylie, M.J., J.P. Fontenot, and L.W. Greene. 1985. Absorption of magnesium and other macrominerals in sheep infused with potassium in different parts of the digestive tract. J. Anim. Sci. 61:1219–1229.
148
Yang, N., C. Liu, A.R. Peck, M.A. Girondo, A.F. Yanac, T.H. Tran, F.E. Utama, T. Tanaka, B. Freydin, I. Chervoneva, T. Hyslop, A.J. Kovatich, J.A. Hooke, C.D. Shriver, and H. Rui. 2013. Prolactin-Stat5 signaling in breast cancer is potently disrupted by acidosis within the tumor microenvironment. Breast Cancer Res. 15:R73-R85
Young, J.W. 1977. Gluconeogenesis in cattle: significance and methodology. J. Dairy Sci. 60:1–15.
Zimpel, R., M.B. Poindexter, A. Vieira-Neto, E. Block, C.R. Staples, W.W. Thatcher, and J.E.P. Santos. 2018. Effect of dietary cation-anion difference (DCAD) on acid-base status and dry matter intake in dry cows. J. Dairy Sci. 101: submitted.
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BIOGRAPHICAL SKETCH
Camilo Lopera Higuita was born July 19, 1991 in Medellin, Colombia. In February
2009, Camilo began studying at the Corporación Universitaria Lasallista and graduated
in July 2015 with a Bachelor of Science in Animal Sciences and Animal Husbandry. In
July 2015 he moved to Gainesville, Florida to start his Master of Science program under
the advisement of Dr. José Eduardo P. Santos in the Animal Sciences Graduate
Program within the Department of Animal Sciences at the University of Florida. Camilo
obtained his Master of Science Degree in May 2018 and returned to Colombia to pursue
a career in the private sector in the animal feeding industry.
