References

1
References
Faverdin, P. 1999. The effect of nutrients on
feed intake in ruminants. Proceeding of the
Nutrition Society. 58523 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.
25523 Five Authors. 1996. Symposium on
Regulation of voluntary forage intake in
ruminants. J. Anim. Sci. 743029-3081. NRC.
1987. Predicting feed intake for food-producing
animals. Washington D.C. National Academy
Press NRC Nutrient Requirements of Beef and
Dairy Cattle publications.
2
Importance of Feed Intake

• Determines level of production
• Production drives ad libitum feed intake
• When less than ad libitum, intake determines
• production
• Used in calculation of production response in
• computer programs
• Affects rate of passage and digestion in the
  rumen
• Determines microbial protein synthesis in the
  rumen
• Important for formulating concentration of
  nutrients
• in diets

3
Traits of Feeds Related to Intake

• Chemical
• Energy concentration
• - ME or NE
• Fiber content
• - NDF
• - Lignin
• Nutrient content
• - N, S, salt
• Added Ionophores
• Physical
• Moisture
• Particle size
• Density

4
Palatability
Characteristic of feed Not all agree that
palatability is a characteristic of feed
alone Stimulates the animal to
respond Taste/flavor Acidity Sweet Aroma/smell Wat
er content Previous experience Feed aversions
5
Animal Factors Related to Feed Intake

• Hunger - Appetite - Smell - Taste Sight
• Body weight
• Physiological state
• Lactation increases
• Pregnancy decreases (Last trimester)
• Temperature stress
• Cold increases and Heat decreases
• Body composition (Increased fat decreases intake)
• Hormones - brain (Leptin Ghrelin)
• Fill of digestive tract
• Energy balance

6
Management Factors Related to Feed Intake
Feeds Accessibility to feed Method of
presentation Frequency of feeding Environment Stre
ss Handling and care Housing conditions Day
length Other Social interactions Hormone
implants Ionophores
7
Theories of Feed Intake RegulationRuminants

• 1. Physical constraints
• Capacity and fill of the digestive tract
• Involved when forage-based diets are fed
• Rate of digestion
• Rate of passage
• 2. Metabolic constraints
• Consume feed to satisfy demands for energy
• Involved when grain-based diets are fed
• Nutrient effects
• Metabolic effects
• 3. Efficiency of oxygen utilization
• Feed is consumed to optimize yield of net energy
  per unit of
• oxygen consumed
• Involved when intake is limited prior to fill
  limiting intake
• 4. Water content of feed
• Consumption of wet feeds is limited to amount
  when water
• requirements are met

8
Regulation of Feed Intake by Ruminants
Physical - - - Fill - - -
Energy
Intake
Dry matter
- - - Metabolic - - -
Nutritive value of feed, NEm
9
Physical Limitations of Fill

• Reticulum-Rumen
• Fill with balloons decreases intake
• 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
• Distention decreases intake of young calves
• Probably not involved in adults (abomasum does
  not
• accumulate digesta in adults)
• Intestines (Infuse methyl cellulose which is not
  digested)
• Dry matter excretion in feces increases
• No effect on feed intake

10
Factors Affecting Fill of Reticulum-Rumen

• Kind of CHOH - starch or fiber
• Rate of digestion and rate of passage
• Lignification of plant material
• Modification of feed
• - Grinding - reduce particle size
• - Chemical - increase rate of digestion
• Treat roughage to make cellulose more available
• - Grinding and pelleting
• 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
• Prediction equations relate feed intake to
  NEm or NDF of diets

11
Metabolic Limitations

• Short-term Signals of satiety determine meal
  size
• Signals to stop consumption
• Chemical and metabolic
• Long-term Concept of energy balance
• Feed is consumed to maintain a constant
• set point or body weight
• Ruminants however will over consume energy
• and accumulate body fat

12
Satiety Signals

• Reticulum-Rumen
• Infuse VFA into rumen decrease size of a meal
• Acetate gt VFA mix gt propionate gt butyrate
• Increased osmolality seems to be a factor
• Intravenous infusion of VFA no effect
• Infuse VFA into portal vein decrease meal size
• Propionate gt butyrate Acetate and glucose no
  effect
• Infuse propionate into intestine decrease meal
  size
• Less effect with glucose
• Some effect with long-chain fatty acids
• Unsaturated gt saturated
• Oxidative metabolism in the liver stimulate
  afferents in vagus
• nerve Signal carried to the brain
• Propionate extensively metabolized in liver
• Little acetate metabolized in the liver
• Glucose converted to lactic acid in intestine
  minimal oxidation
• in the liver
• Unsaturated fatty acids more extensively
  metabolized in the liver

13
Satiety SignalsPhysiological
CNS Ventral medial hypothalamus Stimulation
decreases feed intake Lesions increase feed
intake Lateral hypothalamus Stimulation increases
feed intake Lesions decrease feed
intake Regulatory Peptides Cholecystokinin (CCK)
Decrease feed intake Neuropeptide Y Increase
feed intake Corticotropin-releasing factor
Decrease feed intake Pro-opiomelanocortin
peptides Increase feed intake Enkephalins ?-Endo
rphin Ghrelin Peptide produced in stomach
(abomasum of ruminants) Also produced in
hypothalamus Stimulates release of pituitary
growth hormone Stimulates feed intake Blood
concentrations elevated with fasting
14
Long-term Signals Energy Balance

• Fat mass of the body
• Increased accumulation of fat decreases feed
  intake
• Limitation of space
• Signals
• Leptin
• Peptide produced in adipose cells
• Interacts with receptors in hypothalamus
• Decreases NPY resulting in decreased feed intake
• Related to mass of body fat
• Interaction of short- and long-term signals
• Not well understood
• Long-term signals might alter threshold to
  short-term signals
• Leptin increases sensitivity to CCK

15
Plasma Ghrelin Beef Steers
16
Relationships of Plasma Concentrations of Leptin
and Ghrelin with Backfat Small Frame Angus
Steers
17
Relationships of Plasma Concentrations of Leptin
and Ghrelin with Backfat Large Frame Angus
Steers
18
Effect of Processing Corn Grain and Added Fat on
Feed Intake and Performance
886 lb steers fed steam flaked or dry rolled
corn (8 alfalfa hay) 85 days
19
Effect of Diet Energy and InitialBackfat on Feed
Intake and Performance
975 lb steers fed 25 or 12 alfalfa pellets 70
days
20
Adding Roughage to High-Concentrate Cattle Diets
DMI, BW 1.866 0.0169 Roughage, of DM
r2 0.699 DMI, BW 1.856 0.0275 NDF,
from roughage r2 0.920 DMI, BW 1.858
0.0290 eNDF, from roughage r2 0.931 (JAS
81(E.Suppl. 2)E8-E16, 2002)
21
Effect of Diet Energy and Monensin on Feed Intake
and Performance
665 lb steers fed 12.8 haylage 159 days
22
Effects of Stimulating Production
Increased capacity to produce stimulates feed
intake Hormone implants increase feed
intake Growing/finishing cattle Growth
hormone Dairy cow - increases feed
intake Increased milk production Growing animal -
decreases feed intake Reduces fat deposition
(less energy stored)
23
Effect of Hormone Implants on Feed Intake
829 lb steers fed high concentrate diet (15 corn
silage) 119 days
24
Effects of Lactation
Milk Production
Feed Intake
0 8 16 24 32 40 Week of lactation
25
Environmental Effects on Feed Intake
Dry, minimum mud
120 100 80
Cool night
Normal intake,
Rain Storm Deep mud
Hot night
-10 0 10 20 30 40 Temperature, C
26
Adjustments for Environmental Conditions
Temperature, Adjustment, Lot conditions gt
35 C no night cool -35 gt 35 C with night
cool -10 25 to 35 -10 15 to 25 None 5 to
15 3 -5 to 5 5 -15 to -5 7 lt
-15 16 Some mud, 10 to 20 cm -15 Severe
mud, 30 to 60 cm -30
27
Predicting Feed Intake of Beef Cattle 1996 Beef
NRC
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 Decrease
intake 4 if monensin is being fed Decrease
intake 6 if no implants are used 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
28
Predicting Feed Intake of Dairy Cattle2001 Dairy
NRC
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
29
Predicting Feed Intake of Sheep
Legumes DMI (g/d) BWt.75 (-70.4 182 NEm -
53.2NEm2) Grasses and silages DMI (g/d)
BWt.75 (-81.3 166 NEm - NEm2) Pelleted diets
DMI (g/d) BWt.75 (131 - 18.7NEm) Ensiled feeds
reduce intake of sheep more than cattle. Nursing
twins will increase feed intake up to 50.
30
Feed Intake - Summary
Feed intake equations are only estimates. Feed
intake controlled by many factors. Intakes are
predicted from feed consumption data collected
over an extended period of time, not a specific
point in time. Use experience in projecting feed
intake. Records from similar animals.