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References

References. 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

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  1. References 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. 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 • Water 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 • Stress • 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 > VFA mix > propionate > butyrate • Increased osmolality seems to be a factor • Intravenous infusion of VFA – no effect • Infuse VFA into portal vein – decrease meal size • Propionate > 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 > 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 • -Endorphin • 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 > 35 C no night cool -35 > 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 < -15 16 Some mud, 10 to 20 cm -15 Severe mud, 30 to 60 cm -30

  27. Predicting Feed Intake of Beef Cattle1996 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.

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