Particle Size, Fiber Digestibility, Fragility, and Chewing Response in Dairy Cattle
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Transcript of Particle Size, Fiber Digestibility, Fragility, and Chewing Response in Dairy Cattle
Particle Size, Fiber Digestibility, Fragility, and Chewing Response
in Dairy CattleRick GrantRick Grant
W. H. Miner Agricultural Research InstituteW. H. Miner Agricultural Research InstituteChazy, NYChazy, NY
pef and peNDF: quick review
pef = physical effectiveness factor
% of sample retained on ≥1.18-mm screen when dry sieved
peNDF = physically effective NDF
peNDF = pef x NDF%
Based entirely on particle size
Dry sieving peNDF1.18 and FCM/DMI (Grant, 2008, unpublished)
0.6
0.9
1.2
1.5
1.8
10 15 20 25 30 35 40peNDF1.18 (% of DM)
FCM
/DM
I (kg
/kg)
12 studies using vertical dry sieving (standard procedure)
How well does peNDF system work? (Zebeli et al., 2006)
33 experiments, 1997-2005
Chewing activity peNDF R2=0.44 (0.76,
Mertens) Ruminal pH
peNDF R2=0.67 NDF digestibility
peNDF R2=0.56
Recurring question: can we improve on peNDF system?Is there any value in doing so?
Does all NDF at the sameparticle size elicit the the same chewing response?
NDF Total Chewing ActivityFeed % of DM (min/kg of
DM)(min/kg of
NDF)Alfalfa 49 61 125Dried grass 51 63 123Ryegrass 65 90 139Grass 65 103 158Ryegrass 68 104 152Grass 65 107 165Oat straw 78 163 209Oat straw 79 143 181Oat straw 84 164 195
Chewing and NDF source (Mertens, 1997)
Straw is “concentrated” chewing source
Item 52% 47% 43% 39%
Corn silage 37.3 34.0 31.0 27.9Alfalfa-grass silage 14.5 11.1 5.9 0.6
Wheat Straw - 2.1 6.2 10.3peNDF, % 21.5 20.2 19.2 18.9TCT, min/d 783 780 772 774TCT, min/kg NDF intake 94 92 93 91
(Meyers et al., 2009)
Why differences in chewing response? Forage Fragility Concept
Forage fibers differ in tensile strength, or toughness, and resistance to physical breakdown during chewing
Particles differ in Diameter Lignin & lignin linkages Moisture Digestibility
Forage Fragility How to measure forage fragility
in the lab? Artificial mastication (Troelson and
Bigsby, 1964) Comminution energy required to
grind Shear-force energy required to cut Ball mill: particle size reduction
index
Ball mill method for measuring forage fragility
Equipment Ball mill Jars: 5.5-L Ceramic
cylinders (balls): 2.6-L
Milling time: 15 min at 80 rpm
Ro-Tap: dry vertical sieving apparatus(1.18-mm sieve)
Measuring “fragility” by ball milling forages (Cotanch et al., 2007)
Ball mill with ceramic balls mimics chewing action (Jim Welch, unpublished data)
Measurement of fragility
Fragility determined as Δpef
(pefi – pefBM15)/pefi x 100%
Ranges from 0 (very tough) to 100 (very fragile)
Forage
NDFD24
Original
pef
30-min BMpef
% chang
eGrass silage 1st cut 55.8 60.1 39.3 -34.5
Corn silage 1 42.8 92.0 67.0 -27.2Corn silage 2 35.4 88.9 67.5 -24.1
Grass Hay 1st cut 29.6 84.1 63.1 -25.0Wheat Straw 21.5 99.7 84.8 -14.9
Alfalfa Hay Stems 28.1 95.0 71.6 -24.6Alfalfa Hay Leaves 47.6 41.1 13.0 -68.5
pef values of original sample and ball milled sample with % decrease in pef value (fragility)
(Cotanch et al., 2007)
Forage fragility as measured by % change in pef plotted by NDFd24
(Cotanch et al., 2007)
BMRs
Straws
2030405060708090
20 30 40 50 60NDFD24
% C
hang
e in
pef
"Fra
gilit
y"
NDFd24 versus fragility for grass hays: effect on chewing response
31% NDFD46% Fragility0.13 pef
55% NDFD81% Fragility0.15 pef
(Cotanch et al., 2008)
30-60 min/d TCT
Magnitude of Lactation Responses to Varying Forage Fragility and NDFD
-Hay versus straw-BMR corn silage
Grass hay versus straw: how different are they in stimulating chewing?What does the cow say?
Materials and methods: diets and feeding
Ingredients (% DM) Hay Diet Straw DietHaycrop silage 14.0 14.0Corn Silage 17.7 17.7BMR Corn 15.2 15.21st Cut Hay 6.1 (3.6 lb) 0.0Straw 0.0 5.1 (3.0 lb)Concentrate mix 47.0 48.0NDF, % of DM 34.3 33.8pef of TMR 0.66 0.67peNDF 22.6 22.6
Response to supplemental NDF at similar particle size (Miner Inst., 2009)
DietHay
(3.6 lb)Straw (3.0 lb)
Chemical composition of forages24-h NDFD %Fragility %
pef
3383
0.52
2234
0.53Behavior response
Eating, min/d 250 249Ruminating, min/d 479 505*
Performance responseDMI, lb/d
Protein yield, lb/dFat yield, lb/d
623.53.6
623.5
3.9*
Fragility of BMR versus Conventional Corn Silage Usually approximately 10%-
units greater in NDF digestibility
BMR has 6 to 31% greater fragility than conventional silages as measured with ball milling technique
Fragility of BMR versus Conventional Corn Silage (unpublished, 2010)
Conventional BMRConventional corn silage 43.3 ---
BMR corn silage --- 43.3Haycrop silage 15.0 15.0
Crude protein, % of DM 17.0 17.4peNDF, % of DM 19.2 19.5
Digested starch, % of DM 25.0 22.8DMI, % of BW 3.42 3.75*
SCM, kg/d 37.7 39.7*SCM/DMI, kg/kg 1.49 1.42*
TCT, min/kg NDFI 100 83*Average pH 6.08 5.95*
Rumen pH for cows fed bmr or conventional corn silages in TMR
Particle size does not tell entire story!
Fragility field study: Fragility x 24-h NDFD: Combined forages, 2009
020406080
100120
0 20 40 60 80
NDFD24 %
Frag
ility
%
BMRCS CS HCS SGS Straw
Some practical feeding management considerations . . .
Agri-ChopperAgri-ChopperUses knives to chop Uses knives to chop hayhay
HaybusterHaybusterUses hammer mill with Uses hammer mill with screenscreen
Agri-chopper Haybuster
Type of forage chopper can make a difference
Agri-Chopper HaybusterMeasure Grass
hayWheat straw
Grass
hay
Wheatstra
wpef 0.72 0.80 0.72 0.8424-h NDFD, % 21.3 19.3 31.8 25.0Fragility 19 18 27 23Chewing response, min/d
740 750 700 710
Don’t assess choppers entirely on particle size
Develop adjustment factors for pef
CPM-Dairy 3.0
pef adjustment factor: grass24-h NDFD Fragility Adjustment
factor30 50 0
40 60 -6
50 70 -10
60 80 -19
pef adjustment factor: corn silage24-h NDFD Fragility Adjustment
factor30 65 0
40 75 -7
50 85 -13
60 95 -20
Implications for Ration Formulation High NDFD, high fragility forages
stimulate less chewing per unit of NDF at similar particle size
Need to Feed more total forage Formulate for higher peNDF
Use pef adjustment factor Supplement with lower NDFD, lower
fragility forages Grass, straw
Conclusions NDFD and fragility are related
Can improve our prediction of chewing and performance response
Focus on NDFD
Assessment of forage physical properties shouldn’t stop with a simple particle size measurement
Thank you…