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ENERGY BALANCE AND SYSTEMS

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  1. ENERGY BALANCE AND SYSTEMS

  2. References • Blaxter, K. L. 1989. Energy Metabolism in Animals and Man. Cambidge University Press • Kleiber, M. 1975. The Fire of Life. Krieger Publishing, New York Also Beef, Dairy, and Sheep NRC

  3. Basics of Energy Use in Mammals • Simple • Practical • Energy systems to predict and monitor livestock production • The common thread among human weight loss systems

  4. ENERGY CONCEPTS • Energy - “ability to do work” • Feedstuffs • protein • carbohydrates • lipids • Physics of energy • Priestly 1700’s - the flame and the mouse

  5. Priestly and the discovery of oxygen A candle or an animal can make good air bad. Plants restore to the air whatever breathing animals and burning candles remove.

  6. Early discoveries of relevance • Theory of combustion - Both fire and animals produce the same amount of heat per unit of CO2 • Heat production /unit of O2 produced is a more uniform measurement • 1st law of thermodynamics - energy cannot be created or destroyed

  7. Hess’ Law of Heat Summation • Not concerned with mechanisms or rates of energy change • True for living as well as non-living systems • Forms basis for bioenergetic investigation even if mechanisms of action is unknown FECES URINE GAS HEAT MAINTENANCE PRODUCTION FEED ANIMAL 100% OF ENERGY INTAKE

  8. CO2 ATP-ADP CYCLE FUELS H2O O2 CATABOLISM ADP ATP Pi MECHANICAL WORK Pi TRANSPORT WORK Pi BIOSYNTHETIC WORK

  9. Units of Measure • Calorie - energy required to raise the temperature of 1 g of water 1 degree C (from 16.5 to 17.5) • 1 kilocalorie (kcal) = 1,000 calories • 1megacalorie (Mcal) = 1,000,000 calories • 1kcal/g = 1 Mcal/kg • 1 calorie = 4.184 joules

  10. Bomb Calorimeter

  11. PARTITIONING OF ENERGY Gross Energy (GE) Digestible Energy (DE) Metabolizable Energy (ME) Net Energy (NE) Digestion loss (fecal) Urine loss Combustible gases (CH4) Heat increment (HI) -heat of fermentation -heat of nutrient metabolism NEm -basal metabolism -activity at maintenance -sustaining body temp NEg -retained energy

  12. HEAT LOSS • BASAL METABOLISM • VOLUNTARY ACTIVITY • PRODUCT FORMATION • THERMAL REGULATION • WORK OF DIGESTION • HEAT OF FERMENTATION • WASTE FORMATION AND EXCRETION

  13. BASAL METABOLISM • VITAL CELLULAR ACTIVITY • RESPIRATION • BLOOD CIRCULATION • IONIC BALANCE • TURNOVER OF PROTEINS

  14. RETAINED ENERGY • TISSUE GROWTH • LACTATION • WOOL GROWTH • HAIR GROWTH • PREGNANCY

  15. SYNTHESIS OF BODY TISSUES • FAT contains 9.4 Mcal/kg and 3.8 Mcal/kg is lost as heat • 13.2 Mcal are required to deposit 1 kg fat • PROTEIN contains 5.6 Mcal/kg (muscle=1.1 Mcal/kg) • 7.4 Mcal are lost as heat (1.5 Mcal for muscle) • 13 Mcal are required to deposit 1 kg of protein • 2.6 Mcal are required to deposit 1 kg of muscle

  16. GROSS ENERGY • FEED GE (kcal/g) • Corn meal 4.4 • Oats 4.6 • Wheat bran 4.5 • Timothy hay 4.5 • Clover hay 4.5 • Corn stover 4.3 • Oat straw 4.4

  17. GROSS ENERGY OF FEEDSTUFF COMPONENTS • CARBOHYDRATE 4.2 kcal/g • FAT 9.4 kcal/g • PROTEIN 5.6 kcal/g • ASH 0.0 kcal/g BACON TORCH

  18. Calorimetry • DIRECT - direct measurement of heat production • INDIRECT - calculation of heat production from O2 intake, CO2 release and methane and nitrogen losses • HE = 3.886 02 +1.2 CO2 -.518 CH4-1.231N

  19. Nitrogen Carbon Balance (Indirect) • Required data: dry matter, nitrogen, carbon and energy of feed, feces, urine, methane and carbon dioxide. • Assumed: • 6 g protein/g N • .5254 g carbon/g. protein • 5.6 kcal/g protein

  20. N-C balance cont’ • Carbon gained as fat = Foodc – (Fecesc + Urinec + CO2c + Methanec + Proteinc) • Fat assumptions: • 1.307 g fat/ g carbon • 9.4 kcal/g fat • Heat productionkcal = Intakekcal - (Feceskcal + Urinekcal + Methanekcal +Protein gainedkcal + Fat gainedkcal)

  21. Body Size and Metabolism Kleiber

  22. Armsby Calorimeter

  23. Determination of Nem of timothy hay by a difference trial Armsby (1922) NEm = 2028/4 = 51 Mcal/cwt Of historical importance: 1. H = ME - P 2. Development of comparitive slaughter technique

  24. Lofgreen and Garrett (1968)

  25. NEm DETERMINATION Alfalfa High Item Hay Concentrate Intake at Equilibrium 35 23 Heat Prod. an No Feed 43 43 NEm of the Feed (kcal/g) 1.23 1.87

  26. NEp BY THE "DIFFERENCE TRIAL" ENERGY GAIN NEp + 0 FEED INCREASE

  27. ACTUAL "DIFFERENCE TRIAL" ON HIGH CONC. RATION Level of Feeding Item Equilibrium Free Choice Feed Intake 23 59 Energy Gain 0 40 Differences: Feed Intake, g -- 36 Energy Gain, kcal -- 40 NEp of Feed: kcal per gram -- 1.11

  28. Comparison of Fed and Fasted Steers by Indirect calorimetry (“head box”) Eisemann and Nienaber (Brit. J. of Nutr. 64:399, 1990)

  29. DIGESTIBLE ENERGY (DE) • TOTAL DIGESTIBLE NUTRIENTS (TDN) • 1 lb TDN = 2,000 kcal DE • TDN = DCP + DNFE + DCF + 2.25(DEE) • Estimated from ADF • from truly digestible NFC, NDF, CP and FA • Dairy NRC • (http://www.nap.edu/books/0309069971/html/) • pp. 13-27

  30. CONVERSION BETWEEN DE, ME & NE • ME = .82DE • NEm = 1.37 ME - 0.138 ME2 + 0.0105 ME3 -1.12 • NEg = 1.42 ME - 0.174 ME2 + 0.0122 ME3 -1.65

  31. EFFECT OF ENVIRONMENT ON ENERGY REQUIREMENTS Lower Critical Temperature Upper Critical Temperature THERMONEUTRAL ZONE Cold stress Heat Stress Optimum for Performance and Health High Low EFFECTIVE AMBIENT TEMPERATURE

  32. Lower Critical Temperature • Coat Description LCT • Summer or wet 59 • Fall 45 • Winter 32 • Heavy winter 18

  33. Effective Temperature Temperature Wind Speed -10 0 10 20 30 Calm -10 0 10 20 30 5 -16 -6 3 13 23 15 -25 -15 -5 4 14 30 -46 -36 -26 -16 -6 *Maintenance Requirements increase .7% for each degree of cold stress.

  34. NEp (production) • NEg (gain) • NEc (conceptus) • NEl (lactation)

  35. Beef NRC Gain equations • NEm (Mcal) = .077 WTkg.75 *(environmental adjustment) • EBW = .891 SBW • EBG = .956 SWG • SRW = 478 kg for animals finishing at small marbling • EQSBW = SBW * (SRW)/(FSBW) • EQEBW = .891 EQSBW • RE = 0.0635 EQEBW0.75 EBG1.097 • SWG = 13.91 RE 0.9116 EQSBW-.6837

  36. Using Net Energy for Gain Projection Step 1. Determine dry matter intake of each ingredient Lb. as fed DM fraction Lb DM Corn silage 15 .4 6.0 Corn 7 .85 5.95 SBM 1.5 .9 1.35 Total 23.5 13.3 = X

  37. Using Net Energy for Gain Projection Step 2. Determine NEm intake Lb. DM NEm/lb NEm (Mcal) Corn silage 6 .4 4.44 Corn 5.95 1.02 6.07 SBM 1.35 .93 1.26 Total 13.3 11.77 = X Ration NEm (DM Basis) = 11.77Mcal/13.3 lb DM = .89 Mcal/lb

  38. Using Net Energy for Gain Projection Step 3. Determine NEg intake Lb. DM NEg/lb NEg (Mcal) Corn silage 6 ..47 2.82 Corn 5.95 .70 4.17 SBM 1.35 .63 .85 Total 13.3 7.84 = X Ration NEg (DM Basis) = 7.84Mcal/13.3 lb DM = .59 Mcal/lb

  39. Using Net Energy for Gain Projection Step 4. Determine Lb of DM for maintenance 1. NEm requirement 500 lb. steer = 4.5 Mcal 4.5 Mcal * environmental adjustment (1.3) = 5.85 Mcal required / .89 Mcal NEm per lb of DM = 6.6 lb. of feed dry matter needed for maintenance Environmental adjustment (maintenance ratio) for calf fed in open lot conditions in November in Iowa.

  40. Using Net Energy for Gain Projection Step 5. Determine energy available for gain 1. 13.3 lb DM intake - 6.6 lb (needed for maintenance) = 6.7 lb. of feed DM available for gain. 2. 6.7 lbs of DM X .59 Mcal/lb (NEg) = 3.95 Mcal available for gain.

  41. Using Net Energy for Gain Projection • Step 6 - Determine weight gain • 227 kg steer (low choice at 500 kg) • EQSBW = 227 * (478/500) = 217 kg • SWG = 13.91 * 3.95 0.9116 * 217 -.6837 = 1.23 kg/d • ADG = 1.23*2.205 = 2.71 lb/day

  42. Energy Calculations for Dairy Cattle • NEm = .08 LW.75 - increased for activity • Growing bulls & heifers have 12% higher req than beef • NEm = .086 LW.75 • or use beef equations and increase Maint 7-10% • NEl~NEm because of similar efficiency • Lactation requirement (Mcal/kg) milk • = .0969(percent fat in milk)+.36 • Feed Energy Values discounted for level offeeding • For a comparison of Dairy Energy Systems see: J Dairy Sci 81:830, 840, 846 (1998) Energy Symposium

  43. Dairy NRC Feed Energy Discounts = .18 X -10.3

  44. Energy calculations for Sheep • Maintenance requirement is lower than beef • .056 W.75 • Wool has great insulative value • Fetal number is important (Nep, Mcal/day) Stage of gestation (days) #fetuses 100 120 140 1 .070 .145 .260 2 .125 .265 .440 3 .170 .345 .570

  45. 1996/2001 Beef NRC Model Objectives: • Predict net energy requirements across a continuum of cattle types • Adjust requirements for physiological state • Adjust requirements for environmental conditions • Predict variable lactation requirements • Predict energy reserves fluxes • Describe feeds by fermentation characteristics • Describe rumen and animal tissue N requirements • Compute variable ME and MP from feed analysis • Two levels of solution

  46. Maintenance Requirements

  47. Weight Physiological State Acclimatization Sex Breed Activity Heat or Cold stress External Insulation Coat Condition Wind speed Hide Thickness Internal Insulation Condition Score Age Factors affecting Maintenance

  48. Base NEm Requirement • 77 kcal / (BWkg)0.75 • Adjusted for: • Acclimatization • Sex • Breed • Physiological state • Lactation • Condition Score

  49. Effect of Condition Score on Maintenance Requirement

  50. Energy Requirements vs. Body Weight