ANS/NUTRS 520
February 23,2012
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Faverdin, P. 1999. The effect of nutrients on feed intake in ruminants.
Proceeding of the Nutrition Society. 58:523
Fisher, D.W. 2002. A review of a few key factors regulating voluntary
feed intake in ruminants. Crop Science 42: 1651
Allen, M.S., B.J. Bradford and K.J. Harvatine. 2005. The cow as a model
to study food intake regulation. Annual Review of Nutrition. 25:523
Five Authors. 1996. Symposium on “Regulation of voluntary forage intake
in ruminants. J. Anim. Sci. 74:3029-3081.
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NRC. 1987. Predicting feed intake for food-producing animals. Washington
D.C. National Academy Press
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NRC Nutrient Requirements of Beef and Dairy Cattle publications.
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Physical
- - - Fill - - Energy
Dry matter
- - - Metabolic - - -
Nutritive value of feed, NEm
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• Capacity and fill of the digestive tract
• Involved when forage-based diets are fed
 Rate of digestion
 Rate of passage
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• Consume feed to satisfy demands for energy
• Involved when grain-based diets are fed
 Nutrient effects
 Metabolic effects (Seoane et al., 1972)
Forbes and Provenza, 2000
Reticulum-Rumen
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• Tension receptors located in reticulum and cranial sac of rumen
Increases frequency of discharge of neurons in the ventral
medial hypothalamus and inhibits those in the lateral hypothalamus
Fill of the reticulum-rumen determined by rate of digestion and rate
of passage
Abomasum
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• Probably not involved in adults (abomasum does not
accumulate digesta in adults)
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Rate of digestion and rate of passage
•
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- Grinding - reduce particle size
- Chemical - increase rate of digestion
Treat roughage to make cellulose more available
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▫ More susceptible to microbial attack - Increase rate
of digestion
▫ More susceptible to exit from rumen - Reduced
omasal filtration
▫ Increased uptake of water by feed particles
▫ Change in ruminal location (stratification)
 Lower digestibility in rumen
 Increased intake
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◦ Taste/flavor
 Acidity
 Sweet
◦ Aroma/smell
◦ Water content
◦ Previous experience
 Feed aversions
Villalba & Provenza (1997)
Predicting feed intake of
food-producing animals,
NRC, 1987
Milk Production
Feed Intake
0
8
16
24
Week of lactation
32
40
Dry, minimum
mud
Normal intake, %
120
100
80
Cool night
Rain
Storm
Deep mud
Hot night
-10
0
10
20
Temperature, C
30
40
Predicting feed intake of
food-producing animals,
NRC, 1987
Temperature, or Lot condition
Adjustment, %
> 35 C no night cool
> 35 C with night cool
25 to 35
15 to 25
5 to 15
-5 to 5
-15 to -5
< -15
Some mud, 10 to 20 cm
Severe mud, 30 to 60 cm
-35
-10
-10
None
3
5
7
16
-15
-30
Predicting feed intake of
food-producing animals,
NRC, 1987
Stock et al., JAS 1995
Feedlot
NEm (Mcal/d) = SBW.75 (.2435 NEm - .0466 NEm2 - .1128)
SBW = Shrunk body wt in kg
NEm (Mcal/d)/NEm of diet = kg feed DM
All Forage Diet
DMI (kg/kg BW.75) = 0.002774 %CP - .000864 %ADF + .09826
Initial body weight of feeder cattle
DMI (kg/d) = 4.54 + .0125 IBW
IBW = initial body wt in kg
Breeding cattle
NEm (Mcal/d) = BW.75 (.04997 NEm2 + .04631)
Equation not accurate for feeds with NEm less than 1
Lactating Holstein cows
DMI (kg/d) = (0.372 X FCM + 0.0968 X BW0.75)
X (1- e(-0.192X(WOL + 3.67)))
BW = body wt in kg
FCM = 4% fat corrected milk in kg/d
WOL = week of lactation
e = base of natural log
Growing heifers
DMI (kg/d) = (BW0.75 X (0.2435 X NEm - 0.0466 X NEm2 - 0.1128))/NEm
Legumes
DMI (g/d) = BWt.75 (-70.4 + 182 NEm - 53.2 NEm2)
Grasses and silages
DMI (g/d) = BWt.75 (-81.3 + 166 NEm - NEm2)
Pelleted diets
DMI (g/d) = BWt.75 (131 - 18.7 NEm)