Milk Fever
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Transcript of Milk Fever
DIETARY STRATEGIES TO PREVENT MILK FEVER IN DAIRY CATTLE
MILK FEVER
Parturient paresis syndrome in dairy cattle
as caused by hypocalcemia
CALCIUM METABOLISM
Intake
Feces
Absorption
Plasma Ca Bone
Urine Colostrum/milk/fetus
CLASSICAL DIETARY STRATEGY TO PREVENT MILK FEVER
-Low calcium intake (20-25 g/day) during dry period
-Normal calcium intake (80-100 g/day) around parturition and after that
Low Ca High Ca
Ca intake 47.5 83.7
Ca absorption
g/day 2.2 2.3
% of intake 4.6 2.7
Calcium absorption in dry cows when fed either
low or high Ca rations
MODERN DIETARY STRATEGY TO PREVENT MILK FEVER
-Feeding of ration with negative DCAD (- 50 mEq/kg DM) during dry period
-Change to ration with normal DCAD (> + 200 mEq/kg DM) around parturition
ADVANTAGE OF MODERN VERSUS CLASSICAL STRATEGY :
Ration with negative DCAD raises absolute
calcium absorption
DCAD = Dietary Cation-Anion Difference
DCAD = m Eq (Na + + K +) - (Cl - + S 2-) / kg DM
Effect of a negative DCAD on the incidence of milk fever
Reference DCAD(mEq/kg ds)
Incidence of milk fever(%)
Block, 1984 + 330 47.4
- 128
Oetzel et al, 1988 + 189
- 75
Goff en Horst, 1995 + 450
+ 150
- 150
0
17.0
4.0
47.6
50.0
10.5
n = 19 – 24 / treatment
Influence of NH4Cl on urinary pH
H+ + Cl-
Rumen
ileum
H+ + Cl-
Urine
NH4+ + Cl- NH3 + H+ + Cl-
Liver : urea
Influence of CaCl2 on urinary pH
2 H20 2 OH- + 2 H+
GI-tract
H+ Cl- (Urine)
Ca2+ + 2 Cl-
Ca2+ + 2 OH- Ca(OH)2Feces
Urinary pH and Ca excretion in cows fed rations with either a positive or negative DCAD
+ 276 -170
pH 8.7 7.9
Ca (g/day) 0.4 6.1
DCAD (mEq/kg DM)
Hypothesis : Ration with a negative DCAD increases Ca-absorption
(Schonewille et al, 1994)
Cation-rich Anion-rich
Grassilage (kg dm/day) 5.0 5.0
Cornsilage (kg dm/day) 1.9 1.9
Concentrate (kg dm/day) 1.0 1.1
Ca (g/day) 50 53
Na (g/day) 10 10
K (g/day) 175 175
Cl (g/day) 52 169
S (g/day) 20 24
DCAD (mEq/kg dm) +276 -170
COMPOSITION OF EXPERIMENTAL RATIONS
Cation-rich Anion-rich
(g/day)
Intake 50.4 52.8
Feces 48.6 47.8
Absorption 1.8 5.0*
Urine 0.4 6.1*
Balance 1.4 -1.1
(% of intake)
Absorption 3.6 9.5*
*P<0.05 ( n = 6 in cross-over experiment)
CALCIUM BALANCE AND ABSORPTION
HYPOTHESIS :
The extra flow of Ca through the body after feeding a ration with a negative DCAD, can be used to
maintain the plasma Ca concentration at the onset of milk production
CALCIUM METABOLISM
Intake
Feces
Absorption
Plasma Ca Bone
Urine Colostrum/milk/fetus
Experimental rations
Cation-rich Anion-rich
Grasshay (kg dm/day) 4.6 4.6Cornsilage (kg dm/day) 1.5 1.5Concentrate (kg dm/day) 1.1 1.0Ca (g/day) 37 37Na (g/day) 33 31K (g/day) 160 160Cl (g/day) 79 220S (g/day) 15 15DCAD (mEq/kg dm) +330 -230
Experiment:
- Induction of hypocalcemia by Na2EDTA (0.9 mmol/h) infusion.
- Infusions were finished when plasma Ca not bound to EDTA was about 1.0 mmol/l.
- Measurement of urinary Ca excretion during EDTA infusions (catheter in bladder).
- Concentrations of Ca in plasma and urine were measured colorimetrically in order to obtain the concentration of Ca not bound to EDTA
(Schonewille et al, 1999)
Urinary pH and Ca concentration before the infusion
of EDTA
+330 -230
pH 8.73 5.73*
Ca (mM) 1.8 11.5*
* P<0.05
DCAD (mEq / kg DM)
Plasma Ca
Plasma Ca not bound toEDTA (mM)start of infusion 2.44 2.36
end of infusion 0.99 0.97
Amount of EDTA infused (mmol) 249 303*
* P<0.05
+330 -230
DCAD (mEq / kg DM)
Urinary Ca excretion during EDTA infusion after feeding a ration with a negative DCAD
Uri
nar
y C
a ex
cret
ion
(m
mol
/hou
r)
0.0
1.0
2.0
3.0
4.0
5.0
0 to 1.5 2.3 to 4.1 4.5 to 8.3
Time (hours)
Rations with a negative versus positive DCAD :
- Increase Ca absorption and urinary Ca excretion.
- Increase of the Ca flow through the body; the extra urinary Ca excretion can be reduced when plasma Ca is stressed.
Practical relevance :
- Assume production of colostrum is 10 L. (2 g Ca/L.)
- Extra urinary Ca excretion after feeding ration with negative DCAD is about 6 g Ca /day
- The amount of extra available Ca around parturition is sufficient to support the production of about 3 L. of colostrum.
CONCLUSIONS :
-The reduction of milk fever as induced by a negative DCAD, is explained by an increased absolute absorption of Ca and by immediate availability of the extra Ca flow through the body.
-A negative DCAD can be achieved by the use of NH4Cl, CaCl2, MgCl2 an/or MgSO4.