ENERGY BALANCE AND SYSTEMS

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

Basics of Energy Use in Mammals

• Simple

• Practical– Energy systems to predict and monitor livestock

production– The common thread among human weight loss

systems

ENERGY CONCEPTS

• Energy - “ability to do work”

• Feedstuffs– protein– carbohydrates– lipids

• Physics of energy– Priestly 1700’s - the flame and the mouse

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.

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

Hess’ Law of Heat Summation

FEED ANIMALFECES

URINE

GAS

HEAT

MAINTENANCE

PRODUCTION

100% OF

ENERGY

INTAKE

1. Not concerned with mechanisms or rates of energy change

2. True for living as well as non-living systems

3. Forms basis for bioenergetic investigation even if mechanisms of action is unknown

ATP-ADP CYCLE

CATABOLISM

MECHANICALWORK

TRANSPORTWORK

BIOSYNTHETICWORK

CO2

H2O

FUELS

O2

Pi

Pi

Pi

ADP ATP

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

Bomb Calorimeter

PARTITIONING OF ENERGY

Gross Energy (GE)

Digestible Energy (DE)

Metabolizable Energy (ME)

Net Energy (NE)

Digestion loss (fecal)

Urine lossCombustible gases (CH4)

Heat increment (HI)-heat of fermentation-heat of nutrient metabolism

NEm-basal metabolism-activity at maintenance-sustaining body temp

NEg-retained energy

HEAT LOSS

•BASAL METABOLISM

•VOLUNTARY ACTIVITY

•PRODUCT FORMATION

•THERMAL REGULATION

•WORK OF DIGESTION

•HEAT OF FERMENTATION

•WASTE FORMATION AND EXCRETION

BASAL METABOLISM

•VITAL CELLULAR ACTIVITY

•RESPIRATION

•BLOOD CIRCULATION

•IONIC BALANCE

•TURNOVER OF PROTEINS

RETAINED ENERGY

•TISSUE GROWTH

•LACTATION

•WOOL GROWTH

•HAIR GROWTH

•PREGNANCY

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

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

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

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

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

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)

Body Size and Metabolism

Kleiber

Armsby Calorimeter

Determination of Nem of timothy hay by a difference trial

Feedinglevel

Feedeaten(lb)

ME intake(kcal)

Heat prod.(kcal)

Energygain(kcal)

1 6.2 5788 8062 -2296

2 10.2 9544 9812 -268

Diff. 4.0 3766 1748 2028

Armsby (1922) NEm = 2028/4 = 51 Mcal/cwt

Of historical importance:

1. H = ME - P

2. Development of comparitive slaughter technique

Lofgreen and Garrett (1968)

NEm DETERMINATION

Alfalfa High Item Hay Concentrate

Intake at Equilibrium 35 23Heat Prod. an No Feed 43 43NEm of the Feed (kcal/g) 1.23 1.87

NEp BY THE "DIFFERENCE TRIAL"

+

0

ENERGYGAIN

NEp

FEED INCREASE

ACTUAL "DIFFERENCE TRIAL" ON

HIGH CONC. RATION

Level of FeedingItem Equilibrium Free ChoiceFeed Intake 23 59Energy Gain 0 40

Differences:Feed Intake, g -- 36Energy Gain, kcal -- 40

NEp of Feed:kcal per gram -- 1.11

Comparison of Fed and Fasted Steers by Indirect calorimetry (“head box”)

Fed Fasted

Weight (kg) 339 333

Gas exchange (1/2 h):

Oxygen 197.2 131.0

Carbon dioxide 198.8 96.1

Methane 8.2 1.0

RQ 1.01 0.73

Heat Production

kJ/d per kg BW 147.3 93.7

jJ/d per kg BW0.75 632.6 400.8

Eisemann and Nienaber (Brit. J. of Nutr. 64:399, 1990)

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

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

EFFECT OF ENVIRONMENT ON

ENERGY REQUIREMENTS

EFFECTIVE AMBIENT TEMPERATURE

THERMONEUTRALZONE

Low High

Heat StressCold stress

OptimumforPerformanceand Health

LowerCriticalTemperature

UpperCriticalTemperature

Lower Critical Temperature

•Coat Description LCT

•Summer or wet 59

•Fall 45

•Winter 32

•Heavy winter 18

Effective Temperature

TemperatureWind Speed -10 0 10 20 30Calm -10 0 10 20 305 -16 -6 3 13 2315 -25 -15 -5 4 1430 -46 -36 -26 -16 -6

*Maintenance Requirements increase .7% for each degreeof cold stress.

NEp (production)

•NEg (gain)

•NEc (conceptus)

•NEl (lactation)

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

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 6.0Corn 7 .85 5.95SBM 1.5 .9 1.35

Total 23.5 13.3

X =

Step 2. Determine NEm intake

Lb. DM NEm/lb NEm(Mcal)

Corn silage 6 .4 4.44Corn 5.95 1.02 6.07SBM 1.35 .93 1.26

Total 13.3 11.77

Ration NEm (DM Basis) = 11.77Mcal/13.3 lb DM = .89 Mcal/lb

X =

Using Net Energy for Gain Projection

Using Net Energy for Gain Projection

Step 3. Determine NEg intake

Lb. DM NEg/lb NEg(Mcal)

Corn silage 6 ..47 2.82Corn 5.95 .70 4.17SBM 1.35 .63 .85

Total 13.3 7.84

Ration NEg (DM Basis) = 7.84Mcal/13.3 lb DM = .59 Mcal/lb

X =

Using Net Energy for Gain Projection

Step 4. Determine Lb of DM for maintenance

1. NEm requirement 500 lb. steer = 4.5 Mcal4.5 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 inopen lot conditions in November in Iowa.

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.

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

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 of feeding

•For a comparison of Dairy Energy Systems see:

J Dairy Sci 81:830, 840, 846 (1998) Energy Symposium

Dairy NRC Feed Energy Discounts

00.5

11.5

22.5

33.5

44.5

60 65 70 75 80

Maintenance TDN

Uni

t d

eclin

e p

er m

ulti

ple

of

Mai

nt

= .18 X -10.3

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 1401 .070 .145 .2602 .125 .265 .4403 .170 .345 .570

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

Maintenance Requirements

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

Base NEm Requirement

• 77 kcal / (BWkg)0.75

• Adjusted for:– Acclimatization– Sex– Breed– Physiological state

• Lactation

• Condition Score

Effect of Condition Score on Maintenance Requirement

80%

85%

90%

95%

100%

105%

110%

115%

120%

1 2 3 4 5 6 7 8 9

Condition Score (1-9 scale)

Mai

nte

nan

ce M

ult

ipli

er

Energy Requirements vs. Body Weight

0.00

2.00

4.00

6.00

8.00

10.00

12.00

0 200 400 600 800

Body Weight

NE

m R

equ

ired

, Mca

l/d

Energy Requirements vs. Previous Temp.

50

60

70

80

90

100

110

-20 -10 0 10 20 30 40

Previous Temperature, OC

NE

m R

equ

ired

, M

cal/

BW

0.75

Effect of Breed on Energy Requirements

90%100%

120%

0%

20%

40%

60%

80%

100%

120%

Bosindicus

Bos taurus Dairybreeds

Rel

ativ

e N

Em

Req

uir

ed

Effect of Lactation on Energy Requirements

100%

120%

0%

20%

40%

60%

80%

100%

120%

Non-lactating

Lactating

Rel

ativ

e N

Em

Req

uir

ed,

% o

f B

asal

Maintenance Adjustment for Grazing(based on a 600 kg cow)

100%

110%

120%

130%

140%

150%

160%

0.25 0.75 1.25 1.75

Forage Availability (T/ha)

Mai

nen

ance

Ad

just

men

t

Level

Hilly

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

Body Surface Area vs. Body Weight

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

0 200 400 600 800

Body Weight

Su

rfac

e A

rea,

M2

Effect of Condition Score on Internal Insulation

0

2

4

6

8

10

12

14

1 2 3 4 5 6 7 8 9

Condition Score (1-9 scale)

Inte

rnal

Insu

lati

on

,

Mca

l/M2 /O

C/d

<30

30-183

184-364

>365

Age, d

Effect of Wind Speed and Coat Condition on External Insulation

0

5

10

15

20

25

0 5 10 15 20 25 30

Wind Speed, kph

Ext

ern

al In

sula

tio

n,

Mca

l/M2 /O

C/d

Clean & Dry some mud on lower body

mud on lower body and sides heavily covered with mud

Effect of Wind Speed and Hide Thickness on External Insulation

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30

Wind Speed, kph

Ext

ern

al In

sula

tio

n,

Mca

l/M2 /O

C/d

Thin Hide Medium Hide Thick Hide

Effect of Wind Speed and Hair Depth on External Insulation

05

101520253035404550

0 5 10 15 20 25 30

Wind Speed, kph

Ext

ern

al In

sula

tio

n,

Mca

l/M2 /O

C/d

1 cm 2 cm 3 cm

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

Energy Requirements vs. Current Temp.

0

1

2

3

4

5

6

7

-30 -20 -10 0 10 20 30 40

Current Temperature, OC

Ad

dit

ion

al M

E

Req

uir

ed,

Mca

l/d

LCT = 5

LCT = -5

Assumed SA = 6 M2

and TI = 28 Mcal/M2/OC/d

Environmental Effects on Maintenance RequirementsBeef Cow Wintering Ration (hay @ .90 mcal ME/lb DM)

Hair Coat Code at30oF

Hair Coat Code at10oF

1 3 1 3

HideCode

Wind @ 1 mph

1 1.19 1.19 1.29 1.682 1.19 1.19 1.29 1.553 1.19 1.19 1.29 1.45

Wind @ 10 mph

1 1.22 1.48 1.60 1.942 1.19 1.41 1.47 1.843 1.19 1.34 1.36 1.75

Environmental Effects on Maintenance RequirementsTypical Calf Wintering Ration ( .35 mcal NEg/lb DM)

Hair Coat Code at30oF

Hair Coat Code at10oF

1 3 1 3

HideCode

Wind @ 1 mph

1 1.19 1.47 1.50 2.932 1.19 1.37 1.36 1.803 1.19 1.28 1.29 1.69

Wind @ 10 mph

1 1.41 1.69 1.85 2.202 1.30 1.61 1.71 2.103 1.21 1.54 1.60 2.01

Environmental Effects on Maintenance RequirementsTypical Finishing Ration ( .62 mcal NEg/lb DM)

Hair Coat Code at30oF

Hair Coat Code at10oF

1 3 1 3

HideCode

Wind @ 1 mph

1 1.19 1.19 1.33 1.762 1.19 1.19 1.29 1.633 1.19 1.19 1.29 1.51

Wind @ 10 mph

1 1.24 1.52 1.67 2.032 1.19 1.44 1.54 1.933 1.19 1.36 1.42 1.83

Growth Requirements

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

Relationship between Body Fat & Grade

Marbling % Body USDA CanadianScore Fat Grade Grade

Trace 25.2% Standard A1Slight 26.8% Select A2Small 27.8% Choice A3

NEg Required for Growth

0

1

2

3

4

5

6

7

8

200 250 300 350 400 450 500

Shrunk Body Weight, kg

NE

g M

cal/

d

0.6 kg/d

1.0 kg/d

1.3 kg/d

% Protein in Gain vs. Rate of Gain

0

5

10

15

20

25

200 250 300 350 400 450 500

Shrunk Body Weight, kg

% P

rote

in i

n G

ain

0.6 kg/d

1.0 kg/d

1.3 kg/d

% Fat in Gain vs. Rate of Gain

0

10

20

30

40

50

60

70

80

90

200 250 300 350 400 450 500

Shrunk Body Weight, kg

% F

at i

n G

ain

0.6 kg/d

1.0 kg/d

1.3 kg/d

Shrunk Body Fat

10

12

14

16

18

20

22

24

26

28

30

200 250 300 350 400 450 500

Shrunk Body Weight, kg

% S

hru

nk

Bo

dy

Fat

Body Fat vs. Shrunk Body Weight

10

12

14

16

18

20

22

24

26

28

30

200 250 300 350 400 450 500

Shrunk Body Weight

% B

od

y F

at

Traces

SmallSlight

Birth to Maturity - Protein Composition

0

2

4

6

8

10

12

14

16

18

20

0 200 400 600 800 1000

Shrunk Body Weight, kg

% P

rote

in i

n G

ain

0

20

40

60

80

100

120

Em

pty

Bo

dy

Pro

tein

, kg

%PIG

EBP,kg

Birth to Maturity - Fat Composition

0

10

20

30

40

50

60

70

80

90

100

0 200 400 600 800 1000

Shrunk Body Weight, kg

% F

at i

n G

ain

0

100

200

300

400

500

600

700

Em

pty

Bo

dy

Fat

, kg

%FIG

EBF,kg

5%

15%

25%

100 300 500 700 900

Empty body weight, kg

Em

pty

bo

dy

fat,

%

1 = Angus heifer2 = Holstein heifer3 = Angus steers4 = Holstein steers5 = Angus bulls6 = Holstein bulls

1 2 3 4 5 6

Non-implanted cattle of Fortin et. al., 1980 Non-implanted cattle of Fortin et. al., 1980 (50 heifers, 37 steers and 54 bulls)(50 heifers, 37 steers and 54 bulls)

Calculation of Equivalent Weight

Actual BW x (SRW / FW) = EQSW

Calculation of Retained Energy

RE = 0.0635 x EBW0.75 x EBG1.097

RE = 0.0635 x EQEBW0.75 x EBG1.097

Calculation of Daily Gain

SWG = 13.91 x RE0.9116 x SBW-0.6837

SWG = 13.91 x RE0.9116 x EQSBW-0.6837