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4. 2

'.rhe Intake Of Beef ( Continued )

D . H.

available/ha. ,

ex:r- ·�·ri:nents designed to provide

datl:.1.

fo r es timatine

this filllct:i.on. should include a co rrespond.:i.n::; range in pas ture D . H . levels as well as different levels of ava.i.lable pasture D . M . p e r head,

4.

2. 1

Facto rs

Affecting The ?o tentia.l DaiJ.,y IntAke Of Grazing Ani . .!lRls

A

revi ew o f

li terature indicates

t.hat the po te.::!.ti al C.aily inta.ke

o f gr:-tzine beef ani7nal.s is

a

ra.th.r-�r complex and poorly 1.mO.erstood facet of b eef produc tion.

Bines (

19'70 )

conc luded th at where roughages are fed, intake is

constrained by the speed wi t.h which food pcw.ses through

the

rumen. Henc e size o f the rwaen, \vhich is related to

ani:!lal

livm.J eight

(B:i.nes

1 9'70 )

Hou

l

d limi t dai ly intake , Bines also

c

on.:>idered that t.IJ.e f8.ste r passage of a concentr01te die t throt.tgh the ruuen me<mt that rumen sJ.o;:;e v:ould have little li:ni ting effec

t

on po tential inta.lce of con.cent.r<i tes . In tllis c.1.s e the amow1t o f food E:aten per urri t tiras \.;o uld be rela.ted to the

animal' s

physiological s tate and gene tic make-up .

Rayu10nd

( 1969 )

sugges ted

that

feed quali ty and in particular,

digestibili ty, was a

major

ciete nninant of the vo luntary intake of grazine

animals.

Hov1ever, Hutt.on

( 1963 )

\vo rkine

with

dry dairy cattle , and

UJyatt (

19'70)

wo rkine with sheep , found no cle11r relationship between the digestibility of feed and animal in take \vhe re digestibili ty was above

?O�;,L

Crompton.

( 1 962 )

suggested that the

maximum daily

intake of feed

D.M.

fo r bo th dai ry and beef cattle would be equivalent

to

about

3%

of animal livm1eight. Hutt.on

( 1963 )

sho\.red that this

" 3�

s tandard" could considerably w10.eres timate the intake of lac tating dair.y

c

ows, and over­ es timate the

i

ntake o f dry dai ry cows . In Hut ton ' s work the degree

of fatness the dry s t� ck had attained appeared to affect the level of

voluntary intake .

The

3%

of bodyweight standard, howeve r, s eems

to

��ve been generally accepted by research wo rke rs (

1 )

as a guide to the po tential intake o f

- 70 ...

young grmo�

i

ng beef animals on pa s ture .

In

the absence

of

quantitative data from New Z(-!.'llano beef' grazing trials relating po ten-tial in-take to

pas-ture

and

animA.l

paraJUeters , a simplified indirec t

appro ach .b,as been

used to define the po tential intal-::e of tJ1e er razing a•lit!!als in this

s tud,'!.

The daily

livewei.t;ht eain.s

allowabl A wi thin tJ1e model are limited to the highes t gains thz.

t a re

consitd;en

tly

achieved on couunercial farms. If t

h

e relatj.o nsb.ips within the model betHeen dai ly intake and daily

l iveweit;ht

gain a re corr·ec t , then the po tential levels o f

int-A.ke

implicit i n the model 1.rill only be as

high as

tho.se levels

of intake

ac 11i eved

on

commercia

l

farms .

The po ter1tial

daily livewoight

gains

(intakes)

used ar8 pres ented

ir:o.

Table

4. 5

and

t..lle

implications o f t.rris res tri c tion are discussed mo re

fuJ ly

in Sec tion

4. 5. 1 . 5 .

4 . 2 . 2

F'ac to rs 'l'tili t Affec t ·rne Shape O f The Func tiOL1 H e la

ling

Several

overseas rese:!.rch wo r�wrA b �v8 shown t.h.;:lt. t..l-Ie relationship

beti-Teen pas ture

intake/head/day

and feed

available/head/dD.y is

curvil:i.near.

Hull et al

( 196 1 )

gra z ed beef

animals at 5 s-tocking rates ,.,i th

pas ttue beir1g spelled fo r 35 days between graz ings

.

Over

th

e

12o days o f the

experiment (Hhich

Has repeated over

3 years)

the

animals in

each

s

tocki

r

1g rate

trea"tlnen t

were expos ed

to

a

wide ra:1ge

o

f pas tur�;: av::l i UJ.bi l- i tie s . Hull

�

al found a high c o rrelation b

e

tHeen

the

pas ture

availdble/

head before grazinG and the

intake/head

meas ured as diee

s

tible energy i n- take. This relationship was des c ribed by the func tion :

y :: o .

16

-

0 . 2�

X

. ly

. tak .

)

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