2010. Tema 10 - Material de Lectura 5 - Moe

8/11/2019 2010. Tema 10 - Material de Lectura 5 - Moe

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D I R Y P R O D U C T I O N

E n e rg y M e ta b o l i s m o f D a i ry C a t t l e

P . W . M O E 1

US Department of Agriculture

B e l t s v i l l e

MD 2 7 5

A B S T R A C T

E n e r g y m e t a b o l i s m r e s e a r ch d u r i n g t h e

p a s t 2 5 y r h a s r e s o lv e d m a n y u n c e r t a i n t i e s

o f e n e r g y u s e b y l a c t a t i n g c o w s . U s e o f

m e t a b o l i z a b l e e n e r g y f o r m i l k p r o d u c t i o n

e s s e n t i a l l y is u n a f f e c t e d b y m i l k y i e l d b u t

i s s l i g h t l y i n f l u e n c e d b y i t s s o u r c e .

E s t i m a t e s o f e f f ic i e n c y o f u s e f o r m i l k

p r o d u c t i o n ( 6 0 t o 6 4 % ) a r e l o w e r t h a n

e a r l i e r e s t i m a t e s (6 9 t o 7 0 % ) p r i m a r i l y

b e c a u s e o f l o w e r m a i n t e n a n c e c o s t s .

E f f i c i e n c y o f m e t a b o l i z a b l e e n e r g y f o r

b o d y g a i n i s h i g h e r i n l a c t a t i n g (75 )

t h a n n o n l a c t a t i n g ( 6 0 % ) c o w s . U s e

o f b o d y t i ss u e e n e rg y f o r m i l k p r o d u c t i o n

i s a b o u t 8 2 % e f f i c i e n t . E n d p r o d u c t s o f

d i g e s t i o n c o n t r i b u t e t o v a r i a t i o n i n

e f f i c i e n c y o f f a t t e n i n g a n d i n p a r t i t i o n o f

e n e r g y b e t w e e n m i l k a n d b o d y g a i n i n t h e

l a c t a t i n g a n i m a l .

E n e r g y u s e i n t h e g r o w i n g a n i m a l is

i n f l u e n c e d b y c o m p o s i t i o n o f t is s u e

g a i n ed a n d c o m p o s i t i o n o f t h e d i e t.

E n e r g e t i c e f f i c i e n c y o f p r o t e i n d e p o s i t i o n

i s a p p a r e n t l y m u c h l o w e r t h a n t h a t o f f a t

d e p o s i t i o n . A s u b s t a n t i a l p a r t o f t h e

l o w e r e f f i c i e n c y o f p r o t e i n d e p o s i t i o n is

r e l a t e d t o e n e r g y c o s t s o f p r o t e i n t u r n o v e r .

I n c o m p l e t e d i g e s ti o n o f m i x e d d i e ts a t

h ig h i n t a k e b y l a c t a ti n g c o w s a n d m e t h o d s

t o p r e d i c t e n e r g y p a r t i t i o n a r e s e r i o u s

p r a c t i c a l p r o b l e m s . I n t h e s h o r t t e r m ,

i m p r o v e d m e t h o d s t o p r e d i c t i n t a k e

e f fe c t s o n m e t a b o l i z a b l e e n e r g y o f m i x e d

d i e t s w i l l i n c r e a s e a c c u r a c y o f d i e t

f o r m u I a t io n s . I n th e l o n g e r te r m , m e t h o d s

t o p r e d i c t q u a n t i t ie s o f n u t r i e n ts a b s o r b e d

f r o m t h e g u t w i l l p e r m i t a m o r e f l e x i b l e

a n d a c c u r a t e m e t h o d o f e v a l u a t i n g d ie t s

a n d p r e d i c t i n g a n i m a l p e r f o r m a n c e .

Received June 26, 1980.

1 Rum inan t Nutr i t ion Labora to ry , Animal Sc ience

Insti tute, A gricultural Research, Science and Edu cation

Ad min istration, US DA , Beltsville, MD 20705.

I N T R O D U C T I O N

In 1955 B t a x t e r a n d G r a h a m ( 2 3 ) s ta t e d , I n

t h e p e r i o d s i n c e K u h n a n d K e l l n e r , t h e c o n -

s o l i d a t i o n a n d e x t e n s i o n o f t h e n e t - e n e r g y

p r i n c i p l e , w h i c h m i g h t h a v e b e e n e x p e c t e d t o

h a v e o c c u r r e d a s a r e s u l t o f s u c h b r i l l i a n t w o r k ,

h a s , w i t h s e v e r a l n o t a b l e e x c e p t i o n s , n o t t a k e n

p l a c e . I n s t e a d , t h e p e r i o d h a s b e e n c h a r a c t e r i z e d

b y p o l e m i c a l a r g u m e n t r a r e l y i l l u m i n a t e d b y a n

e x p e r i m e n t a n d h a r d l y e v er b y a c a l o r i m e t r i c

t r i a l . K e l l n e r ' s o r i g i n a l w o r k h a s b e e n r e c a l -

c u l a t e d , r e - e x p r e s s e d a n d , i n s h o r t , s u c k e d d r y .

. . C l e a r l y , i n t h e a s s e s s m e n t o f t h e n u t r i t i v e

v a l u e o f f o o d s , t h e f u t u r e m u s t i n v o l v e e x t e n s i v e

e x p e r i m e n t a t i o n a n d m e a s u r e m e n t r a t h e r t h a n

t h e a l m o s t c o m p l e t e d e p e n d e n c e on p i o n e e r

e v i d e n c e w h i c h h a s c h a r a c t e r i z e d th e p a s t 5 0

y e a r s .

P r o g re s s h a s b e e n c o n s i d e r a b l e i n t h e f i e l d o f

e n e r g y m e t a b o l i s m s i n c e t h o s e w o r d s w e r e

w r i t t e n E f f i c i e n c y o f e n e r g y u s e a n d e n e r g y

r e q u i r e m e n t s h a v e b e e n i d e n t i f ie d m o r e p r e -

c i s e l y . P r o g r e s s i v e l y m o r e i n t e n s i v e e x p e r i -

m e n t a t i o n h a s d e s c r i b e d p h y s i o l o g i c a l a n d

b i o c h e m i c a l b a s e s f o r a n i n c re a s i n g p a r t o f t h e

v a r i a t i o n i n e n e r g y u s e . A l t h o u g h e n e r g y

m e t a b o l i s m h a s b e e n s t u d i e d a t m a n y l ev e ls

f r o m s p e ci fi c b i o c h e m i c a l t r a n s f o r m a t i o n s t o

w h o l e p o p u l a t i o n s o f a n i m a l s , t h i s r e v i e w w i l l

d e a I p r i m a r i l y w i t h e n e r g y u s e i n t h e w h o l e

a n i m a l. A s p e c t s o f e n e rg y m e t a b o l i s m t h a t

r e l a t e to t h e e f f e c t i v e n e s s w i t h w h i c h d a i r y

c a t t l e c o n s u m e a v a r i e t y o f d i e ts f o r g r o w t h ,

r e p r o d u c t i o n , a n d p r o d u c t i o n o f m i l k w il l b e

c o n s i d e r e d .

E n e r g y T e r m i n o l o g y

I n t h e d i s c u s s i o n , t e r m i n o l o g y i s t h a t i n

g e n e r a l u s e . D i g e s t i b l e e n e r g y ( D E ) i s g r o s s

i n t a k e o f e n e r g y m i n u s e n e r g y v o i d e d in t h e

f e ce s . M e t a b o l i z a b l e e n e r g y ( M E ) i s D E m i n u s

e n e r g y i n m e t h a n e a n d u r i n e . Generally M E i s

a n e x p r e s s i o n o f t h e a m o u n t o f e n e r g y a v a i l a b l e

f o r m e t a b o l i s m b y t h e a n im a l , a l th o u g h M E

i n c l u d e s s o m e e n e r g y , e .g . , h e a t o f f e r m e n t a t i o n ,

1981 J Dairy Sci 64 :112 0-1 139 11 20


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ME T ABOL I SM - - 7 5 T H ANNI VE RSARY I SSUE 1 1 2 1

n o t a v a il a b le f o r m e t a b o l i s m a n d d o e s n o t

i n c l u d e s o m e e n e r g y , e . g ., u r i n e e n e r g y , w h i c h

i s a p r o d u c t o f m e t a b o l i s m . T h e t e r m s f o r t h e

p a r t i a l e f f i c i e n c y o f M E u s e d f o r m a i n t e n a n c e ,

l a c t a t i o n , p r o t e i n g a i n , f a t g ai n , a n d g a i n i n

t o t a l t i s s u e e n e r g y a r e k i n , k l , k p , k f , a n d k g .

H e a t i n c r e m e n t ( H I ) is t h e i n c r e a s e in t o t a l p r o -

d u c t i o n o f h e a t a s s o c i a t e d w i t h a n i n c r e a s e i n

t h e c o n s u m p t i o n o f f o o d .

E n e r g y u n i t s a r e c a l o r i e s ( c a l) , k i l o c a l o r i e s

( k c a l = 1 0 0 0 c a l ), o r m e g a c a l o r i e s ( M c a l = 1 0 0 0

k c a l ) f o r t h e c o n v e n i e n c e o f t h e U S r e a d e r

a l t h o u g h m a n y o f t h e o ri g i n a l p a p e r s i n c l u d e d

t h e j o u le ( 1 c a l = 4 . 1 8 4 J ; J = M 2 . k g . s - 2 ) .

T h e S i t u a t i o n 5 Ye a rs A g o

R e v i e w s b y B l a x t e r (1 4 , 1 5 ) a n d R e i d

77,

7 8 ) a n d m a j o r t e x t s b y B l a x t e r ( 1 7 ) a n d K l e i b e r

( 4 7 ) s u m m a r i z e d m u c h o f t h e w o r k o n e n e r g y

m e t a b o l i s m o f d a i r y c a t t le a n d p r e s e n t t h e m o s t

c o m p r e h e n s i v e d e s c r i p t io n s o f t h e e n e r g e ti c s o f

d a i r y c a t t l e a v a i l a b le in t h e i r t i m e . E a r l i e r

s t u d ie s s h o w e d t h a t l a c t a t i o n w a s m o r e e f f i c ie n t

t h a n f a t t e n i n g . R e i d ( 7 8 ) s u m m a r i z e d t h e

a v a i l a b l e c a l o r i m e t r y d a t a a n d c o n c l u d e d t h a t

M E c o n s u m e d i n e xc e s s o f m a i n t e n a n c e w a s

u s e d t o t h e e x t e n t o f 6 9 .3 f o r m i l k p r o d u c t i o n

a n d 5 8 .0 f o r b o d y i n c r e a s e a n d t h a t b o t h

w e r e r e l a t iv e l y c o n s t a n t . G r o w t h w a s t h o u g h t

t o b e m o r e e f f i c i e n t t h a n f a t t e n i n g . E n e r g y

f r o m g r a i n s o r c o n c e n t r a t e f e e d s g e n e r a l l y w a s

a c c e p t e d t o h e u se d m o r e e f f i c i e n tl y th a n

e n e r g y o f f o r a g e s, e s p e c i a l l y f o r g r o w i n g

a n i m a l s . T h i s d i f f e r e n c e a p p e a r e d t o b e r e l a t e d

t o t h e c r u d e f i b e r c o n t e n t o f t h e f o r a g e .

C o n s i d e r a b l e d i s a g r e e m e n t e x i s t e d r e g a r d in g

t h e r e l a t i o n s h ip b e t w e e n e n e r g y i n t a k e a n d

e n e r g y b a l a n c e ( E B ) . W o r k e r s g e n e r a l l y a c c e p t e d

t h a t t h i s r e l a t i o n s h i p w a s c u r v i l i n e a r w h e n d a t a

b o t h a b o v e a nd b e l o w m a i n t e n a n c e w e r e

i n c l u d e d . B l a x t e r (1 5 ) e m p h a s i z e d t h e c u rv i l i n a r

r e l a ti o n s h i p b e t w e e n f o o d c o n s u m e d a n d

e n e r g y r e t e n t i o n a n d i n d i c a t e d t h a t t hi s e ff e c t

w a s a t l e a s t in p a r t f r o m a d e c l i n e in M E v a l u e

w i t h i n c r e a s e d i n t a k e .

A l t h o u g h w o r k h a d d o c u m e n t e d r e d u c e d

d i g e s t i b i l i t y b y l a c t a t i n g c o w s i n c o m p a r i s o n

w i t h t h a t o f c o w s a t m a i n t e n a n c e i n t a k e ,

t h i s e f f e c t w a s n o t a c c e p t e d u n i v e r s a l l y . R e i d

( 7 8 ) e m p h a s i z e d t h e i m p o r t a n c e o f r e d u c e d

d i g e s t i b il i t y a n d i n c r ea s e d b o d y f a t t e n i n g

b y l a c t a t i n g c o w s a t h i g h f e e d i n t a k e s i n e x -

p l a i n in g a p p a r e n t d i m i n i s h i n g r e t u r n s i n f e e d i n g

t r ia l s w i t h l a c t a t i n g c o w s .

C o n s i d e r a b l e u n c e r t a i n t y r e m a i n e d w i th

r e g a r d t o t h e e f f e c t o f d i e t q u a l i t y o r r a t e o f

m i l k p r o d u c t i o n o r r a te o f g r c w t h o n e f f ic i e n c y

o f u se o f M E a n d w h e t h e r d i e t e f fe c t s w e r e

s i m i l a r f o r f a t t e n i n g a n d m i l k p r o d u c t i o n .

T h e s e q u e s t i o n s w e r e o f f u n d a m e n t a l i m -

p o r t a n c e i n p r o v i d i n g a c c u r a t e a n d u s e f u l

f e e d i n g s t a n d a r d s .

T h e s i t u a t i o n i n 1 9 56 c a n b e u n d e r s t o o d

m o s t a d e q u a t e ly b y r e m e m b e r i n g t h a t th e

l i m i t e d c a l o r i m e t r i c d a t a o n l a c t a t i n g c o w s

a t t h e t i m e h a d b e e n o b t a i n e d m a n y y e a r s

p r e v i o u s l y . T h o s e r e s u lt s , a l t h o u g h i m p o r t a n t

a n d a l t h o u g h o b t a i n e d w i t h p r e c i s e m e t h o d s ,

w e r e i n a d e q u a t e t o a n s w e r i m p o r t a n t q u e s t i o n s

r a i s e d a b o u t f a c t o r s a f f e c t i n g e f f i c i e n c y o f

e n e r g y u s e b y c a t t l e . T h o s e r e s u l t s w e r e r e -

c a l c u l a t e d a n d d e b a t e d i n t h e l i g h t o f n e w e r

k n o w l e d g e . N e w i n t e r p r e t a t i o n s w e r e p u t

f o r w a r d w i t h o u t b e n e f i t o f f a c il i ti e s t o t e s t

t h e i r v a l id i t y . N e w e x p e r i m e n t a t i o n w a s n e e d e d .

The Last 5 Years

T h e 2 5 y r s in c e 1 9 5 6 c o i n c i d e s a l m o s t

e x a c t l y w i t h a n e x c e p t i o n a l b u r s t o f e x pe r i -

m e n t a t i o n i n a n i m a l e n e r g e t i c s . I n t h e l a t e

1 9 5 0 's , m a j o r c o m m i t m e n t s t o s u p p o r t e n e r g y

m e t a b o l i s m r e s e a r c h w e r e m a d e i n a n u m b e r o f

c o u n t r i e s i n c l u d i n g t h e U S . T h e i n c r e a s e i n r a t e

o f e x p e r i m e n t a t i o n w i t h l a c ta t i n g c o w s c an b e

a p p r e c i a t e d f r o m t h e f a c t t h a t a t o t a l o f 1 1 0

c o m p l e t e e n e r g y b a l a n c e t r i a l s w i t h 3 8 c o w s ,

i n c l u d i n g a l l r e p l ic a t e s , h a d b e e n c o m p l e t e d i n

a l l o f t h e l a b o r a t o r i e s i n t h e w o r l d b e f o r e 1 9 6 1

( 3 4 ) . S i n c e t h a t t i m e t h e r e s u lt s o f 8 0 6 b a l a n c e

t r i a l s w i t h l a c t a t i n g c o w s h a v e b e e n p u b l i s h e d

f r o m t h e B e l t s vi l le l a b o r a t o r y a l o n e . T o c o -

o r d i n a t e t h e i n c r e a s e d r e s e a r c h a c t i v i t y a n d t o

s h a r e r e s e a r c h p l a n s a n d r e s u l ts , a n I n t e r n a t i o n a l

S y m p o s i u m o n E n e rg y M e t a b o li s m w as h e l d

i n C o p e n h a g e n i n 1 9 5 8 u n d e r t h e s p o n s o r s h i p

o f t h e E u r o p e a n A s s o c i a t i o n o f A n i m a l P r o-

d u c t i o n ( E A A P ) . S u c c e e d i n g s y m p o s i a , h e l d

e v e r y 3 y r , h a v e p r o v i d e d a c o n t i n u i n g f o c u s f o r

e n e r g y m e t a b o l i s m r e s ea r ch . T h e p r o c e e d i n g s o f

t h e s e s y m p o s i a , p u b l i s h e d b y t h e E A A P ,

d o c u m e n t a s u b s ta n t i a l p a r t o f t h e e n e r g y

m e t a b o l i s m r e s e ar c h w i t h f a r m a n i m a l s d u r i n g

t h e l a s t 2 5 y r ( T a b l e 1 ) .

T h e s y m p o s i a i n 1 9 5 8 a n d 1 9 6 1 d e a l t l a r g e l y

Journa l of D airy Science Vol. 64, No. 6 , 1981


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1122 MOE

TABLE 1. Symposia on energy metabolism sponsored by the European Association of Animal Production

(EAAP).

1st

2nd

3rd

4th

5th

6th

7th

8th

Symposium on Energy Metabolism. Principles, Methods, and General

Aspects. Copenhagen, Denmark. 15 -19 September 1958. Publ. by EAAP

(Publ. No. 8) and Statens Husdyrugsudvalg, Copenhagen. Grete Thorbek

and H. Aersoe, ed.

Symposium on Energy Metabolism. Methods and Results of Experiments

with Animals. Wageningen, the Netherlands. 11-15 September 1961.

EAAP Publ. No. 10. E. Brouwer and A.J.H. van Es, ed.

Symposium. Troon, Scotland. May 1964 . Energy Metabolism. Publ.

by Academic Press, New York and London. 1965. K. L. Blaxter, ed.

EAAP Publ. No. 11.

Symposium. Energy Metabolism of Farm Animals. Warsaw, Poland. Sep-

tember 1967. Publ. by Oriel Press, Newcastle upon Tyne, England. 1969.

K. L. Blaxter, J. Kielanowski and Grete Thorbek, ed. EAAP Publ. No. 12.

Symposium. Vitznau, Switzerland. September 1970. Energy Metabolism

of Farm Animals. Juris Verlag, Zurich. A. Schurch and C. Wenk., ed.

EAAP Publ. No. 13.

Symposium. Hohenheim, B.D.R. September 1973. Energy Metabolism

of Farm Animals. Publ. by Universitat Hohenheim Dokumentationsstelle.

1974. K. H. Menke, H. J. Lantzsch, and J. R. Reichl, ed. E A A P Publ.

No. 14.

Symposium. Vichy, France. September 1976. Energy Metabolism of

Farm Animals. Publ. by G. de Bussac, Clermont-Ferrand. M. Vermorel,

ed. E A A P Publ. No. 19.

Symposium. Cambridge, England. September 1979. Energy Metabolism.

Publ. by Butter worths, London. 1980. EAAP Publ. No. 26. L. E. Mount, ed.

with method ology: construction of respiration

chambers, tech niqu es o f gas analysis, and

potential errors in energy balance measurements.

Succeeding symposia dealt increasingly with

presentation of results of animal experiments,

discussion of interpre tations of energy balance

measurements, and proposals for application of

findings in practice including discussions on

feed evaluation and feeding standards. More

recent symposia have dealt progressively less

with feed evaluation and increasingly with

specific factors limiting or causing variation in

energy use by farm animals including more

intensive and physiological experi mental ap-

proaches and newer methods of describing and

interpreting data.

Major advances during this time have been in

identifying und etec ted sources of variation in

energy use, in developing quantitative des-

criptions of known sources of variation, and in

developing recommendations for means of

implementing knowledge of energetics in

practical feeding systems.

f f ec t s o f b s o r b e d N u t r i e n t s

E n e r g e t i c ~ f f i c i e n c y A major improvement

in understan ding the causes of variation in

energy efficiency of animals fed different

diets was the demon strat ion of Armstrong,

Blaxter, and their coworkers (2, 3, 4, 6, 7) that

the heat increment of mixtures of steam

volatile fatty acids (VFA) was influenced

greatly by the propo rtion of acet ate in the

fattening sheep but had less effec t in sheep at

maintenance. The energy of VFA infused singly

into the rumen of fattening sheep was used

with efficien cies of 32.9 for acetic acid,

56.3 for pro pion ic acid, and 61.9 for

butyric acid. Mixtures o f VF A containing 75

and 25 acetic acid were used with 31.8 and

58.1 efficiency. Other studies showed a lower

efficiency (54.5 ) for glucose infused into the

rumen than for that infused into the abomasum

(71.5 ) or jugular vein (72.8 ). These studies

indicated the importance of end products of

digestion as opposed to nutrients consumed in

influencing metabolic efficiency in ruminants.

Journal of Dairy Science Vol. 64, No. 6, 1981


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METABOLISM -- 75TH ANNIVERSARY ISSUE 1123

These studies also suggested that vari ation in

the efficiency with which specific end products

of digestion are metabolized could account for

a substantial part of the apparent difference

between use of fibrous diets and that of diets

contai ning large amou nts of starch. The ap-

parently low efficiency of acetate use in the

fattening animal appeared to account for the

depression in net energy of feeds high in fiber

that had caused Kellner to intr oduce his fiber

correct ion fact or some 50 yr earlier.

More recent experiments indicated that the

proportion of acetate of the rumen fermentatio n

products may n ot explain fully the variation in

use of ME and that in some circumstances

acetate ma y be used efficiently for body gain.

Tyrrell et al. (92) reviewed several experiments

in which acetate apparently was used with

relatively high efficiency for body gain and

reported the results of calorimetric investi-

gations with VFA infusion in mature cows.

They found a difference from the nature of the

basal diet in the partial efficiency of acetate for

body gain. Use of ME from infused acetic acid

was 27% for cows fed 100% hay and

69

for

cows fed a diet of 30% hay.

Orskov et al. (71) reported experiments in

which lambs were sustained entirely by in-

tragastric infusion of VFA, protein, minerals,

and vitamins. For mixtures of VFA with 450 to

750 mmol acetate/mol, efficiency of use was 57

to 64%. They also recalculated the earlier data

of Armstrong and Blaxter and reported that

those results predicted an efficiency of 44 to

50%. Orskov et al. (71) concluded that the

effect of proportion of acetate on efficiency of

energy use in growing animals was, in both

instances, too small to be of practical signifi-

cance.

The differences in the results of Tyrrell et al.

(92) and Orskov et al. (71) remain unresolved.

A partial explanation may be found in the

differing physiological state of the e xperimen tal

animals. Data of Orskov et al. (71) pertain to

growing lambs depositing substantial protein

whereas data of Tyrrell et al. (92) pertain to

fattening in adult cows. Under some conditions

acetate is used with low efficiency for fatt ening

although some questions remain as to exactly

what those conditions are. Also, acetate can be

used efficiently in many instances, especially

with high concent rate diets.

Parti tioning o f Energy.

In only a relatively

few experime nts has the use of individual VFA

in lactation been investigated. Armstrong

and Blaxter (5) in calorimetric studies infused

mixtures of VFA, propionate, and acetate into

the rum en of goats and found efficiencies of

71.4, 72.3, and 65.0% for lactation and 50.3,

52.3, and 44.4% for energy retention in the

nonlactating body. Two particularly important

findings were described in this paper. First,

acetic acid inf usi on resulted in an increase in

milk fat secretion and a decline in body fat

deposition whereas with pro pionic acid infusion

the reverse was true. Second, heat production

was no t changed. This second findi ng led them

to the con clusion that energy reten tion in the

adult ruminant is more efficient accompanied

by the simult aneous process of milk secretion

than in the nonl actat ing animal. The effect of

VFA infusion on energy partition was noted

with lactating cows by Orskov et al. (70) in

calorimetry experiments. Acetic acid infusion

resulted in more milk energy and less gain of

body energy than did propionic acid infusion.

No difference in efficiency was found.

Effects on energy partition in lactation have

been similar with changes in diet. Table 2 shows

results of an experiment by Flatt et al. (36, 37)

in which cows fed a 60:40 ratio of forage to

concentrate produced more milk and lost more

body tissue energy than cows fed a 20:80 ratio.

The ratio of acetate to propio nate in rumen

VFA was also higher on the higher forage diet.

In incremental studies of corn grain and beet

pulp, Tyrrell et al. (89) found a greater per-

centage of the increase in energy balance (milk

plus body tissue) was milk when beet pulp was

added to the diet than when corn was added.

Sutton et al. (82) observed a reduction in

proportion of acetate in rumen VFA and a

reduction in milk fat yield by lactating cows

when the percentage of concentrate was in-

creased from 60 to 90%. At 90% concentrate,

more starch reached the duodenum when

corn grain was fed than when barley was fed.

Live weight gain was also greater on the 90%

corn diet, and milk yield was less. When corn

replaced barley, the contribution of rumen

digestion to overall digestion of energy was

reduced considerably.

Effects of percentage concentrate, percentage

of crude protein, and feed intake on partition

of energy in lactating cows were studied by

Journet et al. (44). The partition of energy into



5/20

1124 MOE

TABLE 2. Influence of hay:grain ratio on partition of energy between milk and body tissuea.

Hay:grain ratio

Item 60:40 40:60 20:80

Metabolizable energy (ME) intake, Mcal 36.12 36.42 34.87

Energy balance, McaI 11.94 12.63 12.16

Milk energy, Mcal 13.94 13.17 10.41

Tissue energy, Mcal - 2.00 - . 54 1.75

Milk fat, 3.5 3.0 2.7

Acetic:propionic 3.32 2.57 2.00

aData from Flatt et al. (36, 37).

milk decreased with increasing percentage of

concentrate and decreasing percentage of milk

fat. They also found that when energy intake

varied around the requirement, about one-third

of the increment of energy went into milk and

two-thirds into body gain. No relationship

between major VFA and milk production was

found, but minor VFA (isobutyric, isovaleric,

and valeric) in the rumen and crude protein in

the diet were related positively to milk pro-

duction.

Variation in the partial efficiency of use of

the energy of VFA is considerably more im-

portant in fattening than in lactation whereas

the effect in the growing animal is less certain.

In the lactating cow, however, amounts of

individual VFA absorbed from the gut can

exert a significant effect on partition of energy

between milk and body tissue. Effects of

variation in amount and type of diet on energy

efficiency and energy partition likely will not

be explained satisfactorily without compre-

hensive knowledge of amounts of specific

nutrients which are absorbed from the digestive

tract.

In ta k e a n d s s o c ia t iv e Ef fe c ts

In take E f fects Although intake effects on

digestibility had been shown early in this

century (29, 41), the practical significance

of this effect by no means was accepted uni-

versally. The question was debated at a sym-

posium in 1965 (26, 34, 76, 79). Brown (26)

cited several instances in which intake effects

on digestibility appeared to be conflicting. He

concluded that although reduced digestibility

had been detected at high intakes of diets

containing large amou nts of concentrates in a

numbe r of experiments, additional inform ation

was needed. Flatt (34) reviewed the information

then available on intake effects on ME value of

diets and concluded that such an effect could

not be documented. In a study of Beltsville

data, Moe et al. (54) also found no intake effect

on ME values of diets conta ining 40, 60, and

80 conce ntrat e for lactating cows. Not unti l

the 1970's did experime ntal results begin

to appear to indicate in a relatively systematic

fashion that ME values of diets for lactating

cows were substant ially lower than the same

diets fed to nonl actating cows at a maintenan ce

intake.

The significance of depression in digestibility

of diets at high int akes by lactati ng cows was

established firmly in extensive digestibility

measurements by Moe et al. (56), Wagner and

Loosli (103), and Ekern (31). Tyrrell and Moe

(86) reviewed these and other studies and

concluded that digestibility of normal diets by

dairy cows was reduced by abo ut 4 for each

increase in intake equivalent to the amount

needed for maintenance. They also concluded

that the rate of redu ctio n in digestibility was

greater for diets containi ng larger percentages

of concentrate although this effect was less

pronounced for diets based on corn silage.

Intake effects are as great with corn silage-based

diets as with other forages when high per-

centages of grains are fed. At lower percentages

of grain, however, intake effects are likely

greater with corn silage diets than for those

cont aini ng other forages.

In a more recent review, Tyrrell (85) cites

evidence that the digestibility of corn silage-

based diets is improved by addition of ground



6/20

METAB OLISM - - 75TH ANNIVERSARY ISSUE 11 25

l i m e s t o n e t o t h e d i e t ( 1 0 9 ) o r b y i n c r e as e d

p r o t e i n c o n t e n t ( 7 4 ) a n d i n a l f a l f a - b a s e d d i e t s

b y i n c r e a s e d p r o t e i n c o n t e n t ( 8 8) .

T y r r e l l a n d M o e ( 8 7 ) r e p o r t e d a r e d u c t i o n i n

d i g e s t i b i l i t y o f c o r n s i l a g e -b a s e d d i e t s s u p p l e -

m e n t e d w i t h e i t h e r c o rn o r b a r l e y gr a in s

f o r l a c t a t i n g c o w s . T h e M E v a l u e o f t h e b a r l e y

d i e t w a s n o t i n f l u e n c e d b y i n t a k e w h e r e a s M E

v a l u e o f c o r n d i e t d e c r e a s e d a t h i g h e r i n ta k e s .

T h e d e c l i n e i n d i g e s t i b i l i t y w a s s im i l a r f o r t h e

t w o d i e t s . T h e d e c l i n e in d i g e s t i b i l i t y o f c e l l u l o s e

a n d h e m i c e l l u l o s e f ra c t i o n s w a s a b o u t 8 p e r -

c e n t a g e u n i t s a n d t h a t o f s t a r c h a b o u t 3 p e r-

c e n t a ge u n i t s p e r u n i t o f m a i n t e n a n c e i n c re a s e

i n i n t a k e .

W h e e l e r a n d N o l l e r (1 1 0 ) r e p o r t e d t h a t a

p a r t o f t h e r e d u c e d d i g e s t i b i l i t y o f e n e r g y in

l a c t a t i n g c o w s c o n s u m i n g c o r n g r a i n a n d

c o r n s i l a g e i n l a r g e a m o u n t s w a s p r e v e n t e d b y

s u p p l e m e n t a t i o n o f th e d i e t w i t h 2 .7 % l im e -

s t o ne . S u p p l e m e n t a t i o n w i t h l im e s t o n e in -

c r e a s e d f e c a l p H , r e d u c e d s t a r c h l o s se s in t h e

f e ce s , a n d i m p r o v e d f e e d e f f i c i e n c y . T h e y

s u g g e s t e d t h a t t h e i n c r e a s e d f e c a l p H r e f l e c t e d a

m o r e f a v o r a b l e in t e s t in a l p H f o r a c t i v i t y o f

p a n c r e a t i c a l p h a a m y l a s e .

P o o s e t a l . (7 5 ) s u p p l e m e n t e d d i e t s o f

l a c t a t i n g c o w s w i t h e i t h e r u r e a o r s o y b e a n o i l

m e a l ( S B O M ) . U r e a w a s e f f e c t i v e i n i m p r o v i n g

d i g e s t i b i l i t y o f d i e t s c o n t a i n i n g 1 1 .6 t o 1 3 .6 %

c r u d e p r o t e i n w h e n a d d e d i n a m o u n t s t o

i n c r e a s e c r u d e p r o t e i n t o 1 3 t o 1 4 . 2 % , b u t

o n l y S B O M w a s e f f e c t i v e a t h i g h e r p e r c e n t s .

T h e s e r e s u l t s s u g g e s t t h a t u r e a i s e f f e c t i v e in

i m p r o v i n g d i g e s t i b i l i t y a t h i g h e r c r u d e p r o -

t e i n i n l a c t a t i n g c o w s t h a n h a d b e e n s h o w n

p r e v i o u s l y f o r n o n p r o d u c i n g a n i m a l s . I m p r o v e d

d i g e s t i o n o f c o r n s i la g e d i e t s b y l a c t a t i n g

c o w s w i t h s u p p l e m e n t a l u r e a a ls o h a s b e e n

s h o w n b y V e r i t e ( 1 0 1 ) .

I n e x p e r i m e n t s w i t h l a c t a t i n g c o w s , T y r r e l l

a n d M o e ( 8 8 ) f o u n d a g r e a t e r e f f e c t o f i n t a k e

o n M E v a l u e a t l o w e r p r o t e i n t h a n a t h i g h e r .

W h e n d i e t s o f a l f a l fa h a y , c o r n , a n d S B O M w e r e

i n c r e a s e d f r o m 1 4 t o 1 7 % c r u d e p r o t e i n b y

s u b s t i t u t i o n o f co r n w i t h S B O M , b o t h D E a n d

M E w e r e i n c r e a s e d a t h i g h i n t a k e s . W h e n

p r o t e i n w a s i n c r e a s e d t o 2 0 % , h o w e v e r , o n l y

D E w a s i n c r e a s e d . W i t h c o r n s i l a g e d i e t s , D E

a n d M E w e r e i n c r e a s e d w h e n c r u d e p r o t e i n w a s

i n c r e a s e d f r o m 1 1 t o 1 4% b u t n o t w h e n c r u d e

p r o t e i n w a s i n c re a s e d f u r t h e r t o 1 7% . A d d i t i o n

o f 2 . 5 % l i m e s t o n e h a d n o e f f e c t o n d i g e s t i b i l i t y

o f e n e r g y in t h e l a t t e r e x p e r i m e n t .

Associa t ive L f fects L a c t a t i n g c o w s u s u a l l y

a r e f e d m i x e d d i e t s r a t h e r t h a n e i t h e r a ll f o r a g e

o r a l l c o n c e n t r a t e . T h e d i g e s ti o n o f m i x e d d i e t s

a t h ig h i n t a k e s c o m m o n l y i s c o m p a r e d w i th

d i g e s t i o n o f t h e s a m e d i e t a t a m a i n t e n a n c e

i n t a k e t o m e a s u r e i n t a k e e f f e c ts . A s s o c i a t i v e

e f f e c t r e f e r s t o d i g e s t i b i l i t y o f a m i x e d d i e t

d i f f e r e n t f ro m t h a t p r e d i c t e d f r o m d i r e c t

m e a s u r e m e n t o f t h e fo r a g e a n d c o n c e n t r a t e

s e p a r a t e l y . I n t a k e e f f e c t s a n d a s s o c i a t iv e e f f e c t s

a r e b a s i c a l l y t h e s a m e t h i n g , t h e i n c o m p l e t e

d i g e s t i o n o f a m i x e d d i e t a t a h i g h i n t a k e . T h i s

i s i m p l i c i t i n t h e e s t a b l i s h e d r e l a t i o n s h i p

b e t w e e n p e r c e n t a g e o f c o n c e n t r a t e a n d i n t a k e

e f f e c t s. T h e i m p o r t a n c e o f a s s o c i a t i v e e f f e c t s

f o r l a c t a ti n g c o w s c o n c e r n s a d d i t i v i t y o f t h e

d i g e s t i b il i t y o f c o m p o n e n t f e e d s i n a m i x e d

r a t i o n . I n f e e d e v a l u a t i o n s t u d i e s , t h e d i g e s t -

i b i l it y o f c o n c e n t r a t e s t y p i c a l l y is m e a s u r e d b y

d i f f e re n c e w i t h n o n p r o d u c i n g a n i m a l s, u s u a l ly

a t a m a i n t e n a n c e i n t a k e . B l a x t e r ( 2 0 ) s u m -

m a r i z e d e x t e n s i v e s t u d i e s o f M E o f d i e ts

c o n t a i n i n g 0 t o 6 0 % c o n c e n t r a t e w i t h s h e e p a t

m a i n t e n a n c e a n d c o n c l u d e d t h a t a s s o ci a t e d

e f f e c t s w e r e n o t a p r a c t i c a l p r o b l e m . A t h i g h e r

f e e d i n t a k e s , h o w e v e r , a s s o c i a t iv e e f f e c t s

c a n b e r e a l. A n e x a m p l e i s d e s c r i b e d b y J o a n n i n g

e t a l. ( 4 3 ) , w h o f o u n d d i g e s t i b i l i t y o f a m i x t u r e

o f c o r n g r a i n a n d c o r n s i la g e w a s 1 1% l es s t h a n

t h a t p r e d i c t e d f r o m d i g e s t i b il i t y o f t h e c o m -

p o n e n t f e e d s m e a s u r e d a t h i gh i nt a k e s. I n t a k e

e f f e ct s o n d i g e s t i b i l it y w e r e o b s e r v e d on m i x e d

d i e t s , b u t n o t w h e n e i t h e r c o r n s i la g e o r c o r n

g r a i n w a s f e d a l o n e . T h e s e d a t a a r e i l lu s t r a t e d i n

F i g u r e 1 .

I n t a k e e f f e c t s h a v e b e e n e x p r e s s e d b y V a n

S o e s t a n d c o w o r k e r s ( 1 0 0 ) b y d e s cr i b in g

d i s c o u n t f a c t o r s , w h i c h r e p r e s e n t t h e re -

d u c t i o n i n d i g e s t i b i l i t y o f s in g l e f e e d s t u f f s

w h e n i n t a k e i s i n c r e a s e d b y a n a m o u n t e q u a l t o

m a i n t e n a n c e . T h e y l i s t e d d i s c o u n t s f o r a l a r g e

n u m b e r o f f e e d s f r o m i n v iv o d a t a a n d i n v i t r o

d i g e s t i o n r a t e s a n d a v a i l a b le p a s s a g e ra t e s . T h e y

c o n c l u d e d t h a t f e e d s o f h i g h e r ce l l w a l l c o n t e n t

a n d o f a l o w d e g r e e o f l i g n i f i c a t i o n t e n d t o h a v e

t h e l a r g e s t d i s c o u n t s . T h e y a l s o s t a t e d t h a t

s t a r c h a d d s t o t h e c e l l w a l l e f f e c t i n c e r e a l

g r a in s . T h e u s e o f d i s c o u n t f a c t o r s f o r i n d i v i d u a l

f e e d s i n c o m p u t i n g t h e a c t u a l d i g e s t ib i l i ty o f

m i x e d d i e ts i n c o r p o r a t e s t h e s u s c e p t i b i l i t y o f

c o m p o n e n t f e e ds t o i n t a k e e f f ec t s . D i s c o u n t

f a c t o r s p r e s e n t e d b y V a n S o e s t e t a l . ( 1 0 0 ) ,

Journ al o f Dairy Science Vol. 64, N o. 6 , 1981


7/20

2 6 M O E

R E L A T I O N S H I P B E T W E E N I N T A K E

E F F E C T A N D A S S O C I A T I V E E F F E C T

85

DRY

M A T T E R

DIGESTIBILITY

65 ;

M I N T E N N C E

NT E A N K A ~~

~ ~I-~/INTAKE1 IW/

,~. EFFECTL~~

/ ASSOCIATIVE

D LJBITUM EFFECT

I N T K E

100 ~ CORN SI LAG E~ 0

O ~ CORN GRAIN ~ 100

Figure 1. Data of Joanning et al. 43) show an

associative effect between corn grain and corn silage

at ad libitum intake but not at lower intake.

however, do not solve the proble m of non-

additivity or associative effects. A useful

extension of the discount concept will be a

procedure for estimating discounts for total

mixed rations so that the interactions between

fiber degradation and use of soluble carbo-

hydrates can be incorporated.

required to produce that product as in Figure 2.

With several physiological processes occurring

simultaneous/y, however, estimates of partial

efficiency for each process are clouded by

experimental error and also by necessary

assumptions. The most troublesome assumption

concerns maintenance. Three alternatives for

estima ting ener getic e ffic iency are in Figure 3.

The estimate may be derived from two or more

EB measurements made above maintenance in

which case the es timat e is by differe nce or

regression. The precision of the estimate is

determined by experimental error and by the

magnitude of the difference in energy intake

and pro duction. Alternativ e metho ds involve an

assumed amou nt of either ME or net energy

NE) required for mainte nance comb ined with

a single estimate of EB at some point above

maintenance. These alternative methods yield

lower errors because no error is associated with

the maintenance estimate. An incorrect as-

sumption regarding maintenance, however, will

introduce a bias. Considerable variation in

published estimates of partial efficienc y is from

differences in assumptions regarding main-

tenance.

P a r t i a l E f f i c i e n c y E s t i m a t i o n

Efficiency is the ratio between energy in the

product formed and the amount of energy

E N E R G Y

B A L A N C E

~ AEB

A M E

M E I N T A K E

E N E R G Y D I R E C T M E A S U R E

BALANCEoI / OFEFFICIENCY

E N E R G Y

B A L A N C

. . . .

M E I N T A K E

~ A S S U M E M E R EQ U IR EM E NT

F O R M A IN T E N A N C E

M E I N T A K E

META BOLIC EFFICIENCY - 3EB

A M E - k

A M I L K

k ; - A M E

k

-- A

GAI N

g A M E

Figure 2. Partial efficiency of metabolizable

energy ME) for production.

. . . . . . A S S U M E N E R E Q U IR E M E N T

F O R M A I N T E N A N C E

M E I N T A K E

Figure 3. Partial efficiency may be estimated by

regression top) or by assumed metabolizable energy

ME) or, net energy NE) required for maintenance.



8/20

METABO LISM - - 75TH ANNIVERSARY ISSUE 11 27

T h e p r o b l e m s a s s o c i a t e d w i t h m a t h e m a t i c a l

e s t i m a t e s o f p a r t i a l e f f i c i e n c y , i n c l u d i n g t h e

c o n c e p t s o f m a i n t e n a n c e , w e r e d i s c u s s e d

e x t e n s i v e l y b y V a n E s (9 5 ) . H e e m p h a s i z e d

l i m i t a t i o n s o f t h e c o n c e p t o f n e t e n e r g y f o r

m a i n t e n a n c e a n d e f f i c ie n c y o f e n e rg y u s e

f o r m a i n t e n a n c e . E n e r g y r e q u i r e d f o r m a i n -

t e n a n c e is p r i m a r i l y f o r t h e p r o d u c t i o n o f A T P ,

a n d t h i s e n e r g y a l o n g w i t h t h e w a s t e d e n e r g y i s

l o s t e v e n t u a l l y a s h e a t. H e a t p r o d u c t i o n a t

m a i n t e n a n c e i s, t h e r e f o r e , t h e t o t a l o f p r o -

d u c t i v e a n d n o n p r o d u c t i v e e n e r g y . H e a t p r o -

d u c e d b y t h e f a s t i n g a n i m a l i s t h e r e s u l t o f

b o d y t i s s u e b e i n g m e t a b o l i z e d t o s u p p l y t h e

e n e r g y n e e d e d t o m a i n t a i n t h e a n i m a l . T h e

r a t i o b e t w e e n f a s t in g a n d m a i n t e n a n c e h e a t

p r o d u c t i o n i s, t h e r e f o r e , a n e x p r e s s i o n o f t h e

r e l a t i v e e f f i c i e n c y o f b o d y t i ss u e e n e r g y a n d

d i e t a r y e n e r g y i n m e e t i n g t h e n e e d s f o r m a i n -

t e n a n c e . E f f i c i e n c ie s c a l c u l a t e d i n s u c h a

m a n n e r s h o u l d b e r e f e rr e d t o a s a p p a r e n t

e f f i c i e n c y a n d b e a r l it t l e r e l a t i o n s h i p t o t h e

e f f i c i e n c y c o m p u t e d f o r e n e r g y u s e a b o v e

m a i n t e n a n c e i n w h ic h a m e a s u r e a b l e e nd

p r o d u c t i s fo r m e d .

V a n E s ( 9 5 ) a l s o d i s c u s s e d e r r o r s a s s o c i a t e d

w i t h e s t i m a t i o n o f m a i n t e n a n c e r e q u i r e m e n t b y

r e g r es s i o n . H e n o t e d t h a t r e g r e s s i o n a n a l y s e s

t h e o r e t i c a l l y r e q u i re t h a t t h e i n d e p e n d e n t

v a r i a b l e( s ) b e m e a s u r e d w i t h o u t e r r o r . I f n o t ,

t h e c o m p u t e d r e g r es s i o n c o e f f i c i e n t s w il l b e

u n d e r e s t i m a t e d . S i n ce M E a n d E B b o t h a r e

m e a s u r e d w i t h e r r o r , i n c l u d i n g s o m e s o u r c e s o f

e r r o r s u c h a s f e c a l, m e t h a n e , a n d u r i n e l o s s e s

t h a t a r e c o m m o n t o b o t h , t h e m o d e l s e le c t e d

w i l l i n f l u e n c e e s t i m a t e s o f p a r t i a l e f f ic i e n c y a n d

t h e e s t i m a t e o f m a i n t e n a n c e .

C r a m e r ( 2 8 ) d e s c r i b e d a n o r t h o g o n a l r e -

g r e ss i on p r o c e d u r e t h a t a c c o m m o d a t e s e r r o r s in

b o t h v a r i ab l e s . I t m i n i m i z e s t h e p e r p e n d i c u l a r

d i s t a n c e s f r o m t h e l i n e t o t h e p o i n t s r a t h e r t h a n

t h e v e r t i c a l d i s t a n c e s f r o m t h e l i n e t o t h e p o i n t s

a s i n c o n v e n t i o n a l r e g r e s s i o n .

B e c a us e o f t h e s o u r ce s o f e r r o r c o m m o n t o

E B a n d M E , a s y s t e m h a s b e e n p r o p o s e d i n

w h i c h r e t a i n e d e n e r g y ( R ) i s r e l a t e d t o gr o s s

e n e r g y i n t a k e ( G ) b y s c a li n g b o t h w i t h f a s t in g

h e a t p r o d u c t i o n i n a g e n e r a li z e d f o r m o f th e

M i t sc h er li ch e q ua t io n R = B ( 1 - e x p ( p G ) ) - l ,

w h e r e t h e p a r a m e t e r s B a n d p a r e f i t t e d b y a n

i t e r a t i v e p r o c e d u r e ( 1 9 , 2 1, 2 2 ) . T h i s t e c h n i q u e

a v o i d s a s s u m p t i o n s r e g a r d i n g m a i n t e n a n c e

r e q u i r e m e n t s b u t r e q u i re s d i re c t m e a s u r e m e n t

o f f a s t in g h e a t p r o d u c t i o n b y e a c h t e s t a n im a l

o r a t a b u l a t i o n o f f a s t i n g h e a t p r o d u c t i o n

a c c o r d i n g t o b r e e d , s i z e , s e x , a n d o t h e r a t t r i -

b u t e s a n d o f th e e n e r g y r e t e n t i o n s a s s o c ia t e d

w i t h g a i n s i n b o d y w e i g h t ,

W i t h t h e i n c r e a s e d a t t e n t i o n t o th e d e s -

c r i p t i o n o f t h e m a i n t e n a n c e c o m p o n e n t i n

g r o w i n g a n i m a ls , W e b s t e r e t al . ( 1 0 6 ) c o m p u t e d

a b a s a l c o m p o n e n t o f m e t a b o l i s m r e l a te d t o

l iv e w e i g ht f r o m E B m e a s u r e m e n t w i t h g r o w i n g

s t ee r s an d c o n c l u d e d t h a t t h e b a s a l c o m p o n e n t

w a s c l o s e l y re l a t e d t o b o d y w e i g h t t o th e

e x p o n e n t . 7 3 4 . T h i s e s t i m a t e w a s , h o w e v e r ,

o b t a i n e d b y c a l c u la t i n g t h e b a s a l c o m p o n e n t

f r o m a s s u m e d r e l a t i o n s h i p s b e t w e e n Q (% M E

i n t h e d i e t ) a n d k m a n d k f ( 1 ) w h i c h i n v o l v e

m a i n t e n a n c e o f m a t u r e a n i m a ls a n d e f f i c ie n c y

o f f a t t en i n g . B e c a u se a c tu a l m e a s u r e m e n t o f

f a s t in g m e t a b o l i s m i n t h e s e a n i m a l s d e c l i n e d

w i t h i n c r e a s i n g w e i g h t w h e n e x p r e s s e d a s

k c a l / k g 73 in a c c o r d w i t h A R C ( 1 ) , t h e a u t h o r s

c o n c l u d e d t h a t t h e s e f i n d i n g s c a s t s e r i o u s d o u b t

o n t h e v a l i d i t y o f u s e o f m e a s u r e d f a s ti n g

m e t a b o l i s m a s a b a s e l i n e f r o m w h i c h t o p r e d i c t

e f f i c i e n c y o f g r o w t h .

T h e u n c e r t a i n t i e s a s s o c i a t e d w i t h s t a t i s t i c a l

p a r t i t i o n i n g o f e n e r g y c o s t i n t h e p r o d u c i n g

a n i m a l in t o m a i n t e n a n c e a n d p r o d u c t i o n

a re c o n s i d e r a b l e . A l t h o u g h n e w e r m a t h e m a t i c a l

t e c h n iq u e s e v e n t u a ll y m a y p e r m i t a b a n d o n m e n t

o f t h e c o n c e p t o f m a i n t e n a n c e , e s p e c i a ll y i n t h e

g r o w i n g a n i m a l , i t i s a u s e f u l a n d n e c e s s a r y

c o m p o n e n t i n d i s c u s s in g e n e r g y u s e b y a n i m a l s

o f d i f f e r i n g p r o d u c t i o n r a t e s . I n t h e d i s c u s s i o n s

t h a t f o l l o w , t h e r e a d e r i s r e m i n d e d t h a t a s-

s u m p t i o n s r e g a rd i n g m a i n t e n a n c e e x e r t c o n -

s i d e ra b l e e f fe c t o n e s t i m a t e s o f p r o d u c t i o n

e f f i c i e n c y .

M a i n t e n a n c e a n d a c t a t io n

C a l o r i m e t r i c e x p e r i m e n t s b y B r o u w e r e t a l .

( 2 5 ) a n d V a n E s (9 4 ) s h o w e d t h a t t h e v a l u e o f

a s e r i e s o f h a y s f o r m a i n t e n a n c e o f c o w s w a s

m o r e c l o s e ly r e la t e d t o t h e i r M E c o n t e n t t h a n

t o s t a r c h e q u i v a l e n t . B l a x t e r ( 1 6 ) s u m m a r i z e d

r e s u l ts o f c a l o r i m e t r i c s t u d i e s w i t h d i e t s r a n g i n g

f r o m p o o r q u a l i t y f o r a g e t o al l c o n c e n t r a t e a n d

c o n c l u d e d t h a t e f f i c ie n c y o f u s e o f M E f o r

m a i n t e n a n c e w a s f a i r l y c o n s t a n t . T h e s e r e s u lt s

s u p p o r t e d t h e c o n c lu s i o n o f R i t z m a n a n d

B e n e d i c t ( 8 0 ) f r o m e a r l i e r c a l o r i m e t r i c s tu d i e s .

B l a x t e r ( 1 6 ) c o n c l u d e d f u r t h e r t h a t t h e e l -

Journa l of D airy Science Vol. 64, N o. 6 , 1981


9/20

1128 MOE

ficiency for maintenance of ME from these

natural feeds was equal to that of VFA infused

into the rumen when a correction was made for

the heat of fermentation of the natural feeds.

These studies showed that the variation in

use of ME for mai ntenan ce was low, but some

variation did exist, presumably in part from

losses in heat of fermentation, which was not

measured in the determination of ME. Agri-

cultural Research Council (1) described variation

in efficiency of use of energy for maintenance

(k m) as a funct ion of percentage of ME in the

diet (Qm) as follows: k m 54.6 + .30 Qm-

A major question, unresolved in earlier

calorimetric investigations, was the extent to

which efficiency of ME for milk production

was influenced by the source of dietary ME.

Initial lactation studies at Beltsville (27) were

with diets of alfalfa hay and concentrates

in ratios calculated to provide 50, 75, and 100%

of estimated net energy (ENE) from the alfalfa.

When maintenance was assumed to be 131 kcal

ME/kg -Ts , efficienc ies of use o f ME in excess of

mai nten ance were 65, 61, and 54%, respectively,

for lactation.

Hashizume et al. (42) found the efficiency

of ME of diets con tai ning 45 and 71% of

concentrate consumed in excess of maint enance

(116.3 kcal/kg vs ) was used with efficiencies of

74.0 and 68.2%, respectively, for milk plus

retained body tissue energy.

Van Es and Nijkamp (98) reported the

results of 41 balance trials with lactating cows

consuming mixed diets of concentrate, silage,

and variable amounts of hay. In these studies,

no effects of percentage of crude fiber or of

crude protein on efficiency of milk product ion

were detected. Also, no differences in util izat ion

of hay and silage of equal ME and protein

content were found. These workers concluded

that ME was used for milk production with an

efficiency (kl) of 54 to 58% and that 10.1 to

11.7 Mcal ME was required for the maintenance

of a 500 kg cow (96 to 111 kcal ME/kg'VS).

Van Es and Nijkamp (98) discussed problems

associated with mathe matical descriptions of

results of experiments with lactating cows in

positive or negative body tissue EB. Relation-

ships between ME intake and milk energy were

studied by multiple regression with separate

terms for body weight, milk energy, tissue

energy gain, and tissue energy loss and by

applying several methods of adjusting to zero

body tissue EB. The various methods yielded

slightly different estimates of efficiency but all

method s indicated a slight increase in efficiency

of ME use for milk production with an increase

in metabolizability of the diet.

An extensive series of EB experiments by

Flatt et al. (37) with Holstein cows producing

up to 49 kg of 4% fat-corrected milk (FCM) per

day and con suming diets of 40, 60, and 80%

concentrate plus alfalfa hay showed no signifi-

cant differences among diets in effi ciency of

use of ME for milk production plus tissue

energy gain. These studies included cows at all

stages of lactation and when non lact atin g and

at both ad libitum and restricted feeding. The

magnitude of changes in body tissue energy

status was far greater than in previous experi-

ments and varied from -20.6 to +18.3 Mcal

body tissue energy per day. Differences due to

diet were in body tissue ba lance; cows on the

highest concentrate diet mobilized less fat in

early lactation and deposited more fat in late

lactation than cows on the highest forage diets

at equal ME intake. The regression of total EB

of milk plus body tissue energy on ME intake

was EB (kcal/kg 7s) = - 93.4 + .66 i .011 ME

(kcal/kg'VS). This equation indicated 66%

utilization of ME and zero EB at 142 kcal

ME/kg vs. Extensive mathematical analyses of

these data led to several conclusions: 1) use of

ME for milk or body tissue gain was relatively

unaffected by milk yield, amount of body

tissue gain (or loss), and stage of lactation; 2)

the major difference among diets as well as

among individual cows was in the amount

consumed and energy partition, i.e., milk

production or fattening, rather than the ef-

ficiency with which ME was used; and 3) the

apparently high maintenance requirement was

not due to milk yield or to lactation per se but

may have been influenced by pregnancy.

The ad libitum feeding of high protein

(19.5%) diets in the experiment of Flatt et al.

(37), although necessary to meet the objectives

of that experiment, provided substantially more

protein than needed for maintenance plus milk

production. The effects of excess protein as

well as the contribution of pregnancy were

studied with all available data from Behsville,

which included 350 trials with lactating cows

and 193 with n onlacta ting cows. The decrease

in EB attributable to intake of nitrogen in

excess of protein required was 7.3 kcal/g excess



10/20

ME T ABOL I SM - - 7 5 TH ANNI VE RSARY I SSUE 1 1 2 9

n i t r o g e n ( 9 0 ). T h e a m o u n t o f M E r e q u i r e d

d u r i n g p r e g n a n c y w a s d e s c r i b e d (5 7 ) b y t h e

e q u a t i o n M E ( k c a l / k g 7 s) = 1 0 0 . 8 + . 5 6 7 e 174t

o n d a y t o f g e s t a t i o n . T h e s e d a t a in d i c a t e

1 1 .5 % e f f i c i e n c y o f M E f o r f e t a l g a in .

M u l t i p l e r e g r e s s i o n a n a l y s i s w e r e u s e d b y

M o e e t a l. (6 2 , 6 3 ) t o d e r i v e e s t i m a t e s o f

m a i n t e n a n c e n e e d s a n d p a r t i a l e f f i c i e n c i e s

o f m i l k p r o d u c t i o n a n d t i s s u e g a i n i n T a b l e s 3

a n d 4 . P a r t i a l e f f i c i e n c i e s o f M E u s e d f o r m i l k

p r o d u c t i o n a n d b o d y g a in i n l a c t a t in g c o w s

w e r e 6 4 a n d 7 5 % a n d e f f i c i e n c y o f m a t e r n a l

b o d y g a i n in n o n l a c t a t i n g c o w s w a s 6 0 % . T h e

e f f i c i e n c y o f u s e o f b o d y t i s s u e e n e r g y f o r m i l k

p r o d u c t i o n b y c o w s i n e a rl y l a c t a ti o n w a s

e s t i m a t e d b y c o m p a r i n g p a r t ia l re g r e ss i o n

c o e f f ic i e n t s r e p r e s e n t i n g t h e a m o u n t o f M E

r e q u i r e d fo r m i l k p r o d u c t i o n a n d t h e a m o u n t

o f d i e t a r y M E s p a r e d b y b o d y t i s s u e l o s s. T h e

e s t i m a t e d c o n v e r s io n o f b o d y t is s u e e n e r g y to

m i l k e n e r g y w a s 8 2 % e f f i c i e n t a n d ~ i k e l y

r e fl e c ts s u b s t a n t ia l d i r e c t i n c o r p o r a t i o n o f b o d y

l i p i d s i n t o m i l k f a t . T h e s e r e s u l t s s h o w e d t h a t

t e m p o r a r y s t o r ag e o f e n e r g y a s b o d y f a t i n l a t e

l a c t a t i o n c o m b i n e d w i t h u s e o f b o d y f a t i n

e a r l y l a c t a t i o n i s n e a r l y a s e f f i c i e n t a s d i r e c t u s e

o f d i e t a r y M E f o r m i l k p r o d u c t i o n

(75

X 8 2 %

= 6 2 % v s . 6 4 %) .

T h e f i n d i n g s d e s c r i b e d in th e p r e c e e d i n g

p a r a g r a p h w e r e u s e d b y M o e e t a I. ( 5 5 ) t o

i d e n t i f y t h e r e l a t io n s h i p b e t w e e n d i e t q u a l it y

a n d e f f i c i e n c y o f m i l k p r o d u c t i o n . E n e r g y o f

d i e t s w a s e x p r e s s e d a s n e t e n e r g y f o r l a c t a t i o n

(N E 1). M a i n t e n a n c e r e q u i r e m e n t s e s t i m a t e d b y

p o o l e d l i n e a r r e g r e s s i o n w i t h i n 3 2 d i e t s f r o m

t h e 3 5 0 t r i a l s w i t h l a c t a t i n g c o w s w e r e 1 2 2 .1

a n d 1 1 1 . 3 k c a l M E o r 7 8 . 9 a n d 6 7 . 7 k c a l N E 1

p e r k g 7s o f b o d y w e i g ht , d e p e n d i n g o n w h e t h e r

M E i n t a k e o r m i l k e n e rg y w a s t h e d e p e n d e n t

v a r i a b l e . B e c a u s e t h e a v e r a g e m e a s u r e d f a s t i n g

h e a t p r o d u c t i o n i n th e B e l t sv i ll e l a b o r a t o r y

( 7 3 . 5 k c a l/ k g 'V S ) w i t h n o n l a c t a t i n g , n o n -

p r e g n a n t d a i r y c o w s f o l l o w i n g a p e r i o d o f

m a i n t e n a n c e f e e d in g (3 5 ) w a s b e t w e e n t h e

r e g r e s s io n e s t i m a t e s ( 7 8 . 9 a n d 6 7 . 7 ) o f t h e NE 1

r e q u i re d f o r m a i n t e n a n c e , t h e a u t h o r s c o n c l u d e d

t h a t t h e a m o u n t o f e n e rg y r e q u i r e d f o r m a i n -

t e n a n c e o f l a c t a t i n g c o w s c o u l d b e d e s c r i b ed

a d e q u a t e l y a s 7 3 k c a l NE 1 ( o r N E m i l k ) / k g Ts

a n d t h a t a s e p a r a t e N E t e r m f o r m a i n t e n a n c e

( N E m ) w a s u n n e c e s s a r y .

W i t h t h a t a s s u m p t i o n , t h e N E 1 o f i n d i v i d u a l

d i e t s w a s s t u d i e d b y r e l a t i n g N E 1 o f d i e t d r y

m a t t e r ( D M ) t o o t h e r e x p r e s s i o n s o f e n e r g y a s

f o l l o w ( r e g r e ss i o n c o e f f i c i e n t -+ S E ) :

N E I ( M c a l / k g D M ) = - - . 1 9 +

( . 7 03 + . 0 2 0 ) M E ( M c a l / k g D M ) ,

N E 1 ( M c a l / k g D M ) = - - . 3 6 +

( . 6 7 7 + .0 2 2 ) D E ( M c a l / k g D M ) , a n d

N E 1 ( M c a l / k g D M ) = - - . 1 2 +

( . 0 2 6 6 + .0 0 1 1 ) T D N ( % o f D M ) .

T h e M E , D E , a r id t o t a l d i g e s t i b l e n u t r i e n t s

( T D N ) i n t h e s e e q u a t i o n s w e r e t h o s e a c t u a l l y

o b s e r v e d i n t h e l a c t a t i n g a n i m a l , a n d t h e

a u t h o r s e m p h a s i z e d t h a t t h o s e r e l a t i o n s h i p s

w e r e n o t a p p r o p r i a t e f o r m e a s u r e m e n t s o f

d i g e s t i b i l i t y a t m a i n t e n a n c e . T h e s e r e s u l t s

i n d i c a t e 6 1 t o 6 4 % e f f i c i e n c y o f M E u s e f o r

m i l k p r o d u c t i o n f r o m n o r m a l d i et s .

I n a r e c e n t a n a l y s i s o f B e l t s vi l le d a t a ( 6 1 ) ,

r e s u l t s o f 3 1 3 e n e r g y b a l a n c e t ri a l s w i t h l a c t a t i n g

c o w s p u b l i s h e d s i n c e 1 9 7 0 w e r e u s e d t o s t u d y

t h e s a m e r e l a t i o n s h i p s . T h e r e l a t i o n s h i p s

b e t w e e n N E1 a n d o t h e r e x p r e s s i o n s o f e n e r g y

f r o m t h i s s e p a r a t e d a t a s e t w e r e :

N E1 ( M c a l / k g D M ) = - . 2 1 +

( .6 97 -+-+ 02 2) M E (M ca l /k g DM ),

N E 1 ( M c a l / k g D M ) = - . 4 1 +

( . 6 7 3 -+ . 0 2 1 ) D E ( M c a l / k g D M ) , a n d

N E1 ( M c a l / k g D M ) = - . 5 1 +

( . 0 3 1 5 -+ . 0 0 1 5 ) T D N ( % o f D M ) .

T h e M E a n d D E e q u a t i o n s a r e v i r t u a l ly i d e n ti c a l

t o t h o s e d e r i v e d e a r li e r w i t h a t o t a l l y d i f f e r e n t

d a t a s e t . T h e c o e f f i c i e n t f o r t h e T D N e q u a t i o n

i s a b o u t 1 8% g r e a t e r t h a n i n t h e e a r l i e r e q u a t i o n ,

i n d i c a t i n g a g r e a t e r e f f e c t o f p e r c e n t T D N o n

N E 1 t h a n i n t h e e a r l i e r d a t a s e t. T h e c h a n g e i n

t h e T D N e q u a t i o n i s u n e x p l a i n e d a l t h o u g h t h e

m o r e r e c e n t d a t a s e t i n c l u d e d s e v e r a l d i e t s

c o n t a i n i n g s i la g e f o r w h i c h d r y i n g l o s s e s a n d

e t h e r e x t r a c t a n a l y se s m a y h a v e i n t r o d u c e d

e r r o r s n o t i n M E a n d D E d a t a . G r e a t e s t r e l i a n c e

s h o u l d b e p l a c e d o n M E a n d D E e q u a t io n s

b e c a u s e t h e y a r e b a s e d o n d i r e c t c o m b u s t i o n o f

w e t m a t e r ia l . F o r p r a c t i ca l u s e t h e M E e q u a t i o n s

g i v en a b o v e c a n b e s i m p l i f e d t o N E I (M c a l / k g

D M ) = - - . 2 + . 7 M E ( M c a l / k g D M ) i n w h i c h M E

h a s b e e n a d j u s t e d f o r i n t a k e a n d a s s o c i a t e d

e f f e c t s .

M a i n t e n a n c e a n d r o w t h

M e a s u r e m e n t o f e n er g y c o s t o f g r o w t h i n

Journa l of Dairy Science Vol. 64, N o. 6 , 1981


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1 1 3 0 M O E

T A B L E 3 . M u l t i p l e r e gr e s si o n a n a l y s is o f m e t a b o l i z a b l e e n e r g y ( M E ) i n t a k e ( M c al M E / d a y ) d u r i n g 5 4 3 e n e r g y

b a l a n c e m e a s u r e m e n t s w i t h d a i r y c o w s a ,

M e t a b o l i c B o d y t i s su e B o d y t i ss u e

b o d y s i ze M i l k e n e r g y g a i n l o s s

( k g 75 ) ( M c a l ) ( M c a l ) ( M c a l ) C o n s t a n t

L a c t . , n e g . b a l a n c e ( N = 1 2 6 , R ~

=.957,

S y . x = 1 . 8 8 6 , M E = 3 0 . 0 6 0 ,+ 9 . 0 M c aI )

C o e f f i c i e n t . 1 5 3 ,+ . O 1 2 1 . 5 1 2 -+ . 0 3 4

A v e r ag e 1 1 4 . 6 1 4 . 8 8 2

L a c t . , p o s . b a l a n c e ( N = 2 2 4 , R u = . 9 5 0 , S y . x = 2 . 0 2 5 , M E = 3 2 . 7 2 6 +- 9 . 0 M c a l )

C o e f f i c i e n t . 1 3 5 ,+ . 0 0 9 1 . 5 7 6 + . 0 2 9 1 . 3 7 8 ,+ . 0 5 4

A v e r a g e 1 1 3 . 0 9 . 4 1 6 3 . 2 8 8

D r y c o w s , n e g . b a l a n c e ( N = 7 5 , R 2 - . 7 0 7 , S y . x = l . 7 3 5 , M E = I O . 4 0 1 ,+ 3 .1 M c a l )

C o e f f i c i e n t . 0 5 0 -+ . 0 1 5

A v e r a g e 1 2 9 . 9

D r y c o w s , p o s . b a l a n c e ( N = 1 1 8 , R 2 = . 8 9 7 , S y . x = l . 5 0 3 , M E = 1 8 . 1 4 0 ,+ 4 . 6 M c a l )

C o e f f i c m n t . 0 8 9 ,+ . 0 1 1 1 . 7 0 3 -+ . 0 5 8

A v e r a g e 1 2 8 . 1 3 . 1 6 0

L a c t a t i n g c o w s ( N = 3 5 0 , R 2 = . 9 5 2 , S y . x = l . 9 8 5 , M E = 3 1 . 7 6 6 + 9 . 0 M c a l )

C o e f f i c i e n t . 1 4 1 +- . 0 0 7 1 . 5 5 2 ,+ . 2 2 1 . 3 3 9 ,+ . 0 4 5

A v e r a g e 1 1 3 . 6 1 1 . 3 6 6 2 . 1 0 1

D r y c o w s ( N = 1 9 3 , R 2 = . 9 1 1 , S y . x = l . 6 7 6 , M E = 1 5 . 1 3 3 ,+ 5 .6 M c al )

C o e f f i c i e n t . 0 7 2 ,+ . 0 0 9 1 . 6 7 7 -+ . 0 5 5

A v e r a g e 1 2 8 . 8 1 . 9 3 2

A l l c o w s ( N = 5 4 3 , R 2 = . 9 6 8 , S y . x = 2 _ 0 7 5 , M E = 2 5 . 7 4 0 ,+ 1 1 . 5 M c a l)

C o e f f i c i e n t . 1 0 4 . 0 0 6 1 . 6 2 3 ,+ . 0 1 4 1 . 4 7 3 ,+ . 0 3 6

A v e r a g e 1 1 9 . 8 7 . 3 9 8 2 . 0 4 5

1 . 2 7 0 ,+ . 0 4 5 - - 2 . 8 8 9

- - 5 . 4 7 9

- - 1 . 8 8 9

. 9 9 0 -+ . 0 9 1 6 . 7 8 1

- - 2 . 9 0 4

1 4 0 1

1.279 . 0 3 4 - -2 .152

- - 1 . 9 7 2

. 9 3 3 -+ . 0 6 5 3 . 6 7 0

- 1 . 1 2 8

1 . 2 3 4 +- . 0 2 8 . 6 2 2

- 1 . 9 37

a D a t a f r o m M o e e t a l . ( 6 2 ) .

c a t t l e i s m a d e d i f f i c u l t b y t h e c o m b i n e d e f f e c t s

o f a p p a r e n t d e c l i n i n g m a i n t e n a n c e n e e d s as t h e

a n i m a l a p p r o a c h e s m a t u r i t y a n d t h e c h a n g e s i n

c o m p o s i t i o n o f t i s s u e d e p o s i t e d w i t h a g e a n d

l e v e l o f f e e d i n g . F a s t i n g h e a t p r o d u c t i o n o f

c a t t l e w h e n e x p r e s s e d p e r u n i t o f m e t a b o l i c s i z e

d e c l i n e s w i t h a g e a s i n T a b l e 5 . V a r i o u s e x -

p o n e n t s o f b o d y w e i g h t h a v e b e e n u s e d t o

d e s c r i b e m e t a b o l i c s i ze ( 4 7 ) . E v e n s m a l l d if f e r -

e n c e s i n e x p o n e n t p r o d u c e l a rg e d i f f e r e n c e s in

e s t i m a t e s a s c a n b e s e e n b y c o m p a r i n g f a s t i n g

h e a t p r o d u c t i o n e x p r e s s e d p e r u n i t w e i g h t

r a i s e d t o t h e e x p o n e n t s . 7 3 a n d . 7 5 i n T a b l e 5 .

A s o r t o f g e n t l e m a n ' s a g r e e m e n t t o e x p r e s s

r e s u l t s o f E B m e a s u r e m e n t s b y t h e e x p o n e n t

. 7 5 w a s r e a c h e d a t t h e th i r d S y m p o s i u m o n

E n e r g y M e t a b o l i s m . T h i s a g r e e m e n t w a s i n -

t e n d e d t o f a c i l i t a t e c o m p a r i s o n s o f r e s u l t s f r o m

T A B L E 4 . E s t i m a t e s o f m a i n t e n a n c e r e q u i r e m e n t a n d p a r t ia l e f f i c ie n c y o f e n e r g y u s e in t h e d a i r y c o w a .

M E b f o r M i l k T i s s u e M i l k

m a i n t e n a n c e f r o m M E f r om M E f r o m t is s ue

N (k ca l /k g Ts ) (%)

L a c t a t i n g c o w s 3 5 0 1 2 2 6 4 . 4 7 4 . 7 8 2 . 4

N o n l a c t a t i n g c o w s 1 9 3 1 0 0 5 9 . 6

a D a t a f r o m M o e e t a l . ( 6 2 ) .

b M E i s m e t a b o l i z a b l e e n e r g y .

J o u r n a l o f D a i r y S c i e n c e V o l . 6 4 , N o . 6 , 1 9 8 1


12/20

METABO LISM - - 75TH ANNIVERSARY ISSUE 1 131

TABLE 5. Preferred fasting heat production of catt le .

Age of Body Fast ing metabo l ism

animal a weight b

(mo nths ) (kg) (kcal/kg.73 a)

(kcal/kg'~S c)

55 140 129

3 80 135 124

6 150 125 113

12 275 110 98

18 400 100 89

24 525 95 84

36 650 90 79

48 650 85 70

48 650 80 70

aFrom A RC (1) .

bsug gested mean bod y weights of growing large breed dairy ca tt le for correspon ding ages, f rom N RC (66).

CRecalculated from Columns 2 and 3.

d i f f e r e n t l a b o r a t o ri e s . T h e u s e o f b o d y w e i g h t

i n k g T s r e d u c e s v a r i a t io n f r o m m a t u r e b o d y

s i z e i n f a s t i n g h e a t p r o d u c t i o n a n d p r e s u m a b l y

m a i n t e n a n c e r e q u i r e m e n t . T h e u s e o f m e t a b o l i c

b o d y s iz e to p a r t i t i o n e n e r g y u s e b e t w e e n

m a i n t e n a n c e a n d p r o d u c t i o n i s a p p a r e n t l y l es s

s u i t a b l e f o r t h e y o u n g g r o w i n g a n i m a l t h a n f o r

a d u lt s . R e c e n t w o r k o n t h e p a r t i ti o n a n d

e n e r g y c o s t o f p r o t e i n a n d f a t g a in a n d w o r k o n

t h e e n e r g y c o s t o f p r o t e i n t u r n o v e r , h o w e v e r , is

h e l p i n g t o c l a r i f y e n e r g y t r a n s a c t i o n s i n y o u n g

g r o w i n g a n i m a l s .

S e v e r a l r e c e n t r e v i ew s d i s c u s s m a n i p u l a t i o n

o f g r o w t h ( 3 2 ) , e n e r g y c o s t o f g r o w t h ( 5 2 ) , a n d

n u t r i t i o n a n d g e n e t i c e f fe c t s o n b o d y c o m p o s i -

t i o n ( 5 0 ) .

T h o r b e k ( 8 3 ) c o m p u t e d e f f ic i e n c ie s f o r

b o d y g a i n i n g r o w i n g p i g s w i t h B r i e r e m ' s ( 2 4 )

e s t i m a t e o f m a i n t e n a n c e n e e d s , 1 9 6 . 3 k c a l M E

p e r k g -s 6 b o d y w e i g h t . D e c l i n e i n e f f i c i e n c y

o f M E f o r g a i n w a s l i n e a r w i t h i n c r e a s i n g

p e r c e n t a g e o f t o t a l g a i n a s p r o t e i n . U s i n g a

l i n ea r f u n c t i o n f o r m a i n t e n a n c e M E ( 1 6 83 +

8 . 1 L W f o r l i v e w e i g h t s ( L W ) b e t w e e n 2 0 a n d

9 0 k g) , T h o r b e k ( 8 4 ) f o u n d p a r t i a l e f f i c i e n c i e s

f o r p r o t e i n a n d f a t d e p o s i t i o n o f 4 3 a n d 7 7 .

K i e l a n o w s k i a n d K o t a r b i n s k a ( 4 6 ) s t u d i e d

s e v er a l e x p o n e n t s o f b o d y w e i g h t i n d e s c r ib i n g

r e l a ti o n s h i p s b e t w e e n M E i n t a k e o r h e a t

p r o d u c t i o n a n d p r o t e i n a n d f a t g a i n i n g r o w i n g

p ig s. T h e y f o u n d t h e e x p o n e n t . 7 3 4 f i t b e s t a n d

u s e d . 7 5 f o r s i m p l i c i t y . E n e r g y c o s t o f p r o t e i n

d e p o s i t i o n w a s 1 6 k c a l M E / g , a n d c o s t o f f a t

d e p o s i t i o n w a s 1 3 k c a l M E / g . T h o s e e s t i m a t e s

c o r r e s p o n d t o p a r t i a l e f f i c i e n c i e s o f a b o u t 3 5

a n d 7 1 , r e s p e c t i v e l y .

P a r t i a l e f f i c i e n c y o f p r o t e i n a n d f a t ga i n i n

g r o w i n g l a m b s ( 3 0 t o 6 0 k g ) w a s e s ti m a t e d

f r o m E B a n d f a s ti n g m e a s u r e m e n t s o f h e a t p r o -

d u c t i o n ( 1 0 ) . P a r t i a l e f f i c ie n c i e s w e r e 7 6 f o r

m a i n t e n a n c e , 35 f o r p r o t e i n g a i n , a n d 9 9 f o r

f a t g a in w h e n a w e i g h t e x p o n e n t o f . 7 5 w as

u s e d . R e c e n t w o r k w i t h c a lv e s ( 7 2 ) a n d w i t h

b u l l s a n d h e i f e r s ( 3 8 ) a l s o s h o w s a l o w e r

e n e r g e t i c e f f i c i e n c y f o r p r o t e i n g a i n t h a n f o r f a t

ga in .

M i l l w a r d e t a l . ( 5 2 ) e m p h a s i z e d t h a t s t a t i s -

t i c a l id e n t i f i c a t i o n o f h e a t p r o d u c t i o n a s s o c i a t e d

w i t h p r o t e i n a n d f a t d e p o s i t i o n , a l t h o u g h u s e f u l

t o p r e d i c t g r o w t h p e r f o r m a n c e i n a n im a l s , i s

a r g u a b l y m i s l e a d i n g i n m e c h a n i s t i c t e r m s .

P r o t e i n a n d f a t d e p o s i t i o n s a r e n o t c o m p l e t e l y

i n d e p e n d e n t e v e n t h o u g h f a t d e p o s i t i o n is

l i k e l y m o r e m a n i p u l a b l e t h a n p r o t e i n d e p o si -

t i o n . I f s o m e f a t i s d e p o s i t e d a s a n i n s e p a r a b l e

c o m p o n e n t o f l e a n ti s su e g r o w t h , t h e c o s t o f

t h a t f a t d e p o s i t i o n w i l l be s t a t i s t i c a l l y i d e n t i f i e d

w i t h p r o t e i n d e p o s i t i o n a n d t h e e f f ic i e n c y o f

p r o t e i n s y n t h e s i s t h e r e b y w i l l b e u n d e r -

e s t i m a t e d .

T h e c o n t r i b u t i o n o f p r o t e i n t u r n o v e r t o t h e

a p p a r e n t l y h i gh c o s t o f n e t p r o t e i n s y n t h e s is

a n d t h e h i g h e r r a t e o f m e t a b o l i s m i n y o u n g

g r o w i n g a n i m a l s ha s b e e n t h e s u b j e c t o f r e c e n t

i n t e n s e s t u d y . T h i s t o p i c w a s c o n s i d e r e d i n

d e t a i l b y W a t e r l o w e t a l. ( 1 0 5 ) . T h e y p r e s e n t e d

Journa l of D airy Science Vol. 64, No. 6 , 1981


13/20

1 1 3 2 MOE

e v i d e n c e f r o m r a t s t h a t p r o t e i n t u r n o v e r

d e c l i n e s w i t h a g e a n d t h a t p r o t e i n d e g r a d a t i o n

i s g r e a t e r i n a n i m a l s g r o w i n g m o r e s l o w l y .

E d m u n d s a n d B u t t e r y ( 3 0 ) p r e s e n t e d d a t a

s h o w i n g s u b s t a n t i a l d i f f e r e n c e s a m o n g s p e c i f i c

t i ss u e s in t h e f r a c t i o n a l r a t e ( p e r d a y ) i n p r o t e i n

s y n t h e s i s ; . 0 5 8 f o r l e a n t i s s u e , .4 7 5 f o r b r a i n ,

a n d i n t e r m e d i a t e r a t e s f o r o t h e r t i s s u e s . T h e y

a l so i n d i c a t e d t h a t t h e r a t i o o f s y n t h e s i s t o

d e p o s i t i o n w a s 3 : 1 . T h e c l a r i f i c a t i o n o f t h e r o l e

o f p r o t e i n t u r n o v e r i n t h e g r o w i n g a n i m a l

w i l l, h o p e f u l l y , b e o f c o n s i d e r a b l e v a lu e i n

p a r t i t i o n i n g e n e r g y c o s t s i n y o u n g g r o w i n g

c a t t l e .

A n o t h e r i m p o r t a n t f a c t o r i n i d e n t i f y i n g

e n e r g y n e e d s o f t h e g r o w i n g a n im a l i s t h e

e x t e n t t o w h i c h b o d y c o m p o s i t i o n i s i n f l u e n c e d

b y n u t r i t i o n a l m a n i p u l a t i o n . M a n y d i e t a r y

e f f e c t s h a v e b e e n s u m m a r i z e d c o n c i s e l y b y

B l a c k ( 1 2 ) f o r th e g r o w i n g l a m b . H i s d a t a

s u g g e s t t h a t a n i m a l s g r o w n a t h i g h e r n u t r i t i o n

w i l l h a v e h i g h e r b o d y f a t t h a n a n i m a l s g r o w n

m o r e s l o w l y a l t h o u g h t h e d i f f e r e n c e i n c o m -

p o s i t i o n b e c o m e s p r o g r e s s i v e l y l e ss as t h e

a n i m a l a p p r o a c h e s m a t u r i t y . P r o t e i n c o n t e n t o f

t h e b o d y i n c r e a s e d p r o g r e s s i v e l y a s p r o t e i n

c o n t e n t o f t h e d i e t ( p e r c e n t o f M E ) w a s i n-

c r e a s e d f r o m 6 % t o 1 0 , 1 5 , a n d 2 0 % . T h i s

r e s p o n s e t o p r o t e i n s t e a d i l y d e c l i n e d w i t h

i n c r e a s i n g b o d y w e i g h t . P r o t e i n a b o v e 1 0% o f

M E h a d l i , t l e e f f e c t o n c o m p o s i t i o n o f la m b s

w e i g h i n g o v e r 3 0 k g .

T y r r e l l e t a l. (9 1 ) p a r t i t i o n e d g a i n o f H e r e f o r d

h e i f e r s i n t o p r o t e i n a n d f a t b y c a r b o n a n d

n i t r o g e n b a l a n c e i n a n i m a l s in fa s t a n d w h e n

g i ve n m a i n t e n a n c e a n d a d l i ti b u m i n t a k e.

R e g r e s s i o n o f f a t d e p o s i t i o n o n t o t a l e n e r g y

d e p o s i t e d i n d i c a t e d t h a t 95 o f t h e c h a n g e i n

E B w a s f r o m c h a n g e i n f a t r e t e n t i o n a n d o n l y

5

f r o m c h a n g e i n p r o t e i n r e t e n t i o n .

T h e l i m i t a t i o n o f e n e r g y r e t e n t i o n a l o n e as

t h e e x p r e s s io n o f p r o d u c t i v i t y in g r o w t h is

a p p a r e n t f r o m r e s u lt s o f T y r re l l a n d W a l d o

( 9 3 ) a n d W a l d o a n d T y r r e l l ( 1 0 4 ) . I n c a l o r i-

m e t r i c a n d g r o w t h s t u d i e s t h e y f e d d i r e c t

c u t o r c h a r d g r a s s s i l a ge w i t h o r w i t h o u t a

m i x t u r e o f . 12 % f o r m a l d e h y d e a n d . 1 4% f o r m i c

a c i d . E a c h s i la g e w a s f e d a l o n e a n d s u p p l e m e n t e d

w i t h f o r m a l d e h y d e - t r e a t e d s o d i u m c a s e i n a t e

a n d f e d t o H o l s t e i n s te e r s . T r e a t m e n t o f t h e

s il ag e o r s u p p l e m e n t a t i o n w i t h c a s ei n i m p r o v e d

n i t r o g e n r e t e n t i o n b u t d i d n o t i n f l u e n c e e n e r-

g e t i c e f f i c i e n c y . I n c r e a s i n g i n t a k e o f i n s o l u b l e

p r o t e i n i n c re a s e d t h e p r o p o r t i o n o f g a in a s

p r o t e i n f r o m 3 8 t o 5 1 % o f t o t a l c a l o r i e s g a i n e d .

i s c r e t e E f f e c t s o n E n e r g y U s e

M a n y s o u r c e s o f e n e r g y l o ss a re i n c l u d e d i n

t h e d i s c u s s i o n o f e n e r g e t i c e f f i c i e n c y p r e s e n t e d

a b o v e . M a n y o f t h e s e h a v e b e e n s t u d i e d s p e c if i -

c a l ly , a n d t h e i n f o r m a t i o n g a i n e d h a s i m p r o v e d

o u r u n d e r s t a n d i n g o f t o t a l u se o f e n e rg y b y

c a t t l e . W e b s t e r e t a l . ( 1 0 7 ) d i s c u s s e d s e v e r a l

c o m p o n e n t s o f h e a t in c r e m e n t ( H I ) i n c l u d in g

t h e c o s t o f e a t i n g a n d r u m i n a t i n g , t h e h e a t

p r o d u c e d b y r u m e n f e r m e n t a t i o n , a n d t h e

i n c r e a s e d h e a t p r o d u c e d b y t h e t i s s u e s o f t h e

g u t a n d t h e l i v e r . H e c i t e d a r a n g e i n e n e r g y

c o s t s o f e a t i n g o f 2 . 5 c a l / k c a l M E f o r g r a ss

p e l l e t s a n d 3 6 c a l / k c a l M E f o r f r e s h g r a ss . H e

c o n c l u d e d t h a t t h e e n e r g y c o s t o f ru m i n a t i n g

c o u l d b e d i s c o u n t e d a s a c o n t r i b u t i o n t o H I.

W e b s t e r e t al . ( 1 0 8 ) e s t i m a t e d h e a t o f

f e r m e n t a t i o n i n

v ivo

i n sh e e p a n d f o u n d 6 8 c a l

h e a t p r o d u c e d p e r k i l o c a l o r i e o f d ig e s t i b l e

e n e r g y fr o m f o r a g e d i e ts . H e f o u n d n o d i f f e r e n c e

d u e t o d i e t s o u r c e in t h e a m o u n t o f h e a t

p r o d u c e d b y t h e t i ss u e s o f t h e g u t , b u t h e a t

p r o d u c t i o n i n c r ea s e d e x p o n e n t i a l l y w i t h i n-

c r e a s i n g M E i n t a k e . A t a n i n t a k e o f 1 4 3 . 4 k c a l

M E / k g T s, h e a t

produc t i on

i n t h e t i ss u e s o f t h e

g u t w a s 2 7 k c a l / k g Ts p e r 2 4 h . F a s t i n g h e a t

p r o d u c t i o n o f g u t t i s s u e s w a s 1 5 k c a l / k g v s.

T h e H I d u e t o f e e d i n g in t h e g u t w a s , t h e r e f o r e ,

1 2 k c a l / k g T s o f w h i c h 7 k c a l w a s f e r m e n t a t i o n

h e a t a n d 5 k c a l w a s a e r o b i c m e t a b o l i s m i n t h e

g u t t i s su e s . W e b s t e r e t a l. ( 1 0 7 ) c o n c l u d e d t h a t

p r o c e s s e s o f

ingest ion

a n d d i g e s t i o n c a n a c c o u n t

f o r a b o u t 2 5 t o 3 0 % o f t o t a l H I a n d t h a t m o s t

o f t h e v a r i a t i o n in t o t a l H I m u s t b e fr o m t h e

n a t u r e o f s u b s t r a t e s m a d e a v a i l a b l e b y d i g e s t i o n

a s s u g g e s t e d b y A r m s t r o n g a n d B l a x t e r ( 2 , 3) .

E n v i r o n m e n t a l t e m p e r a t u r e s i n f l u e n c e t o t a l

e n e r g y u s e i n s e v e r a l d i f f e r e n t w a y s . Y o u n g

( 1 1 2 ) r e v i e w e d e f f e c t s o f c o l d e n v i r o n m e n t o n

e n e r g y u s e a n d e m p h a s i z e d t h a t th e r m a l s tr e s s

is d e s c r i b e d t o o f r e q u e n t l y i n t e r m s o f t e m p e >

a t u r e a l o n e . H e c i t e s L e e ' s ( 4 9 ) c o m p i l a t i o n o f

e n v i r o n m e n t a l v a r ia b l e s ( t e m p e r a t u r e , h u m i d i t y ,

a ir m o v e m e n t , r a d i a t io n , p r e c i p i t a t i o n ) , a n i m a l

c h a r a c t e r i s t i c s ( s p e c i es , a g e a n d s e x , b r e e d a n d

t T p e , m e t a b o l i c s t a t e , c o a t , a c c l i m a t i z a t i o n ,

n u t r i t i o n a n d h y d r a t i o n , d e r a n g e m e n t a n d

d i s ea s e , i n d i v i d u a l v a r i a b i l i t y ) a n d c r i t e r ia o f

e f f e c t ( p r o d u c t i v i t y , g r o w t h , r e p r o d u c t i v i t y ,

Journa l of D airy Science Vol. 64, N o. 6 , 1981


14/20

METABO LISM - 75TH ANNIVERSARY ISSUE 1133

p h y s i o l o g i c a l r e s p o n s e , p a t h o l o g i c a l p a t t e r n s )

t o i l lu s t r a te t h e c o m p l e x i t y o f d e s c r i b i n g o r

p r e d i c t i n g e n v i r o n m e n t a l e f f e c t s . T h i s t o p i c is

c o v e r e d e x t e n s i v e l y in a s e p a r a t e p a p e r i n

t h i s i s s u e , s o I w i l l n o t p u r s u e t h e t o p i c h e r e .

M o s t e n e r g y m e t a b o l i s m r e s e a r ch h a s b ee n

u n d e r c o n d i t i o n s o f t h e r m a l n e u t r a l i t y s o

t h a t e n v i r o n m e n t a l e f f e ct s m u s t b e c o n s i d e r e d

i n a p p l y in g th e d a t a t o e x t r e m e c o n d i t i o n s . O n e

s p e c i f ic e f f e c t , h o w e v e r , s h o u l d b e m e n t i o n e d

h e r e b e c a u s e i t a p p e a r s t o o p e r a t e o v e r a w i d e

r a n ge o f e n v i r o n m e n t a l c o n d i t i o n s . T h is e f fe c t

i s a r e d u c t i o n i n d i g e s t i b i l i t y w i t h d e c r e a s i n g

t e m p e r a t u r e . Y o u n g ( 1 1 2 ) c i t e s s e v e ra l e x p e r i -

m e n t s i n w h i c h t h e m e a n r e d u c t i o n i n D M

d i g e s t i b i l i t y w a s 1 . 8 p e r c e n t a g e u n i t s p e r 1 0 C

r e d u c t i o n i n t e m p e r a t u r e . K e n n e d y e t a l. ( 4 5 )

r e p o r t e d t h a t d e c r e a s i ng t e m p e r a t u r e h a d t h e

e f f e c t o f i n c r e a s i n g r a t e o f p a ss a g e o f r u m e n

i n g e s ta , w h i c h d e c r e a s e d o r g a n i c m a t t e r d i ge s -

t i o n b u t i m p r o v e d e f f ic i e n c y o f s y n th e s i s o f

m i c r o b i a l p r o t e i n .

Improvements in Research Techniques

I n n o v a t i o n o r d e v e l o p m e n t i n r e l a t e d f ie l d s

h a s h ad a p r o f o u n d e f f e c t o n t e c h n i q u e s

a v a i l a b l e t o r e s e a r c h e r s i n e n e r g y m e t a b o l i s m .

I m p r o v e d s u rg i ca l t e c h n i q u e s a n d d e v e l o p m e n t

o f i n t e g r a t e d e l e c t r o n i c c i r c u i t s a n d i n e x p e n s i v e

c o m p u t e r s h a v e h a d a p r o f o u n d e f f e c t o n

c o l l e c t i o n a n d a n a l y s i s o f p e r t i n e n t d a t a.

R e c e n t r e vi e w s d o c u m e n t t h e d e v e l o p m e n t a n d

u s e o f s e v e r al t e c h n i q u e s .

T h e i n c r e a s e d u s e o f i n t e s t i n a l l y c a n n u l a t e d

a n i m a l s h a s a l l o w e d i d e n t i f i c a t i o n o f s i t e o f

d i g e s t i o n a n d d i s a p p e a r a n c e o f n u t r i e n t s

f r o m s p e c i f ic s e g m e n t s o f t h e g u t ( 5 1 ) . T h e

i n c r e a s e d a v a i l a b i l i t y a n d u s e o f m a r k e r s h a s

p e r m i t t e d s y s t e m a ti c s t u d y o f t h e d y n am i c s

o f f o o d p a r t i c l e d e g r a d a t i o n a n d p a s s a g e

t h r o u g h t h e g u t ( 33 ). M e t h o d s o f m e a s u r i n g

b l o o d f l o w h a v e b e e n u s e d t o m e a s u r e q u a n t i -

t a t i v e l y u p t a k e o f n u t r i e n t s f r o m t h e g u t ( 9 ,

4 8 ) . I m p r o v e d a n a l y t i c a l s e n s i t i v i t y a n d a u t o -

m a t e d a n a ly s i s h a v e i m p r o v e d t h e a b i l i t y t o

i d e n t i f y a n d q u a n t i f y i n t e r m e d i a r y m e t a b o l i t e s .

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