ENERGY BALANCE AND SYSTEMS

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ENERGY BALANCE AND SYSTEMS
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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

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Basics of Energy Use in Mammals

• Simple
• Practical
• Energy systems to predict and monitor livestock
  production
• The common thread among human weight loss systems

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ENERGY CONCEPTS

• Energy - ability to do work
• Feedstuffs
• protein
• carbohydrates
• lipids
• Physics of energy
• Priestly 1700s - the flame and the mouse

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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.
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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

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

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Bomb Calorimeter
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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
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HEAT LOSS

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

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BASAL METABOLISM

• VITAL CELLULAR ACTIVITY
• RESPIRATION
• BLOOD CIRCULATION
• IONIC BALANCE
• TURNOVER OF PROTEINS

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RETAINED ENERGY

• TISSUE GROWTH
• LACTATION
• WOOL GROWTH
• HAIR GROWTH
• PREGNANCY

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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 (muscle1.1 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

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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

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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

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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

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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

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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)

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Body Size and Metabolism
Kleiber
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Armsby Calorimeter
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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
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Lofgreen and Garrett (1968)
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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
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NEp BY THE "DIFFERENCE TRIAL"
ENERGY GAIN
NEp

0
FEED INCREASE
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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
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Comparison of Fed and Fasted Steers by Indirect
calorimetry (head box)
Eisemann and Nienaber (Brit. J. of Nutr. 64399,
1990)
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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

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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

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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
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Lower Critical Temperature

• Coat Description LCT
• Summer or wet 59
• Fall 45
• Winter 32
• Heavy winter 18

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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.
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NEp (production)

• NEg (gain)
• NEc (conceptus)
• NEl (lactation)

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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

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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
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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
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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
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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.
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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.
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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 1.232.205 2.71 lb/day

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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
• NElNEm because of similar efficiency
• Lactation requirement (Mcal/kg) milk
• .0969(percent fat in milk).36
• Feed Energy Values discounted for level of
  feeding
• For a comparison of Dairy Energy Systems see
• J Dairy Sci 81830, 840, 846 (1998) Energy
  Symposium

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Dairy NRC Feed Energy Discounts
.18 X -10.3
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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
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1996 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

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Maintenance Requirements
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Factors affecting Maintenance

• Weight
• Physiological State
• Acclimatization
• Sex
• Breed

• Activity
• Heat or Cold stress
• External Insulation
• Coat Condition
• Wind speed
• Hide Thickness
• Internal Insulation
• Condition Score
• Age

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Base NEm Requirement

• 77 kcal / (BWkg)0.75
• Adjusted for
• Acclimatization
• Sex
• Breed
• Physiological state
• Lactation
• Condition Score

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Effect of Condition Score on Maintenance
Requirement
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Energy Requirements vs. Body Weight
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Energy Requirements vs. Previous Temp.
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Effect of Breed on Energy Requirements
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Effect of Lactation on Energy Requirements
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Estimation of Heat Production and Calculation of
Lower Critical Temp (LCT)

• Calculate Feed for Maintenance (FFM)
• NEm Req./ NEm Diet FFM
• Calculate Feed for Production (FFP)
• DMI - FFM FFP
• Calculate Net Energy of Production (NEP Tot)
• NEP Diet x FFP NEP Tot
• For growing finishing NEP Diet NEg Diet
• For other animals NEP Diet NEm Diet
• Calculate Heat Production (HP)
• MEIntake - NEP Tot HP, Mcal

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Body Surface Area vs. Body Weight
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Effect of Condition Score on Internal Insulation
Age, d
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Effect of Wind Speed and Coat Condition on
External Insulation
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Effect of Wind Speed and Hide Thickness on
External Insulation
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Effect of Wind Speed and Hair Depth on External
Insulation
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Estimation of Heat Production and Calculation of
Lower Critical Temp (LCT)

• Calculate Heat Loss (HL)
• HL HP / SA, Mcal/M2
• Calculate Total Insulation (TI)
• TI EI II, Mcal/M2/OC/d
• Calculate Lower Critical Temp (LCT)
• LCT 39 - (HL x TI), OC
• Calculate Heat Production
• MEIntake - NEP Tot Heat Production

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Energy Requirements vs. Current Temp.
Assumed SA 6 M2 and TI 28 Mcal/M2/OC/d
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Environmental Effects on Maintenance
RequirementsBeef Cow Wintering Ration (hay _at_ .90
mcal ME/lb DM)
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Environmental Effects on Maintenance
RequirementsTypical Calf Wintering Ration ( .35
mcal NEg/lb DM)
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Environmental Effects on Maintenance
RequirementsTypical Finishing Ration ( .62 mcal
NEg/lb DM)
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Growth Requirements
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Factors we must account for to predict NEg
required in North America

• Genotype - over 80 types have been identified
• Sex
• Feedlot steers, heifers bulls
• Replacement heifers
• Bulls
• Cows
• Implant combinations
• Feeding systems

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Relationship between Body Fat Grade
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Small
Slight
Traces
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Non-implanted cattle of Fortin et. al., 1980 (50
heifers, 37 steers and 54 bulls)
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Calculation of Equivalent Weight
Actual BW x (SRW / FW) EQSW
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Calculation of Retained Energy
RE 0.0635 x EBW0.75 x EBG1.097
RE 0.0635 x EQEBW0.75 x EBG1.097
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Calculation of Daily Gain
SWG 13.91 x RE0.9116 x SBW-0.6837
SWG 13.91 x RE0.9116 x EQSBW-0.6837