Grazing behavior of rangeland beef cows differing in milk production
by William James Lathrop
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in
Animal Science
Montana State University
© Copyright by William James Lathrop (1985)
Abstract:
It was the purpose of this study to evaluate the differences in grazing behavior among straight Hereford
(HH), 50% Angus-50% Hereford (AH), 50% Simmental-50% Hereford (1 SIH) and 75%
Simmental-25% Hereford (3S1H) lactating cows. A total of 48 cows were divided into two groups,
each group containing six cows from each of the four breed types. The study consisted of four 1 0-d
grazing periods starting on July 22 and ending on August 30. Cow weight (BW), calf weight (CW) and
milk production (MP) estimates were taken prior to periods 1 and 4., Cow condition was estimated
using the weight/height ratio and the average calf age was 105 days (range, 85 to 124 days). Cows
roamed freely in a 320 ha pasture with slopes ranging from 5 to 40%. Vibracorders and pedometers
were used to estimate time spent grazing and distance traveled, respectively. During periods 1, 2 and 4,
the 48 study cows were located on a daily basis between 600-900 hr by the use of an aerial photo map.
From the recorded locations, distribution of grazing was calculated for each cow. The overall daily
grazing mean was 9*4 hr/d (633 observations). No significant breed type differences were found in
daily grazing hours. Breed type means were 9.2, 9.6, 9.2 and 9.3 hr/d for HH, AH, 1 SIH and 3S1H
cows, respectively. Daily grazing hours increased from 8.0 hr/d in period 1 to 10.0 hr/d in period 4. Of
the cow and calf traits used as covariates, only MP and calf age had any significant effects on time
spent grazing. The partial regression coefficients for MP and calf age were .05 hr/d/kg/d and -.02
hr/d/d, respectively (adjusted for BW). The increase in grazing time due to increased MP was mainly
between 2400-300 hr. The overall distance traveled mean was 4.7 km/d (82 observations) and followed
the same trend as time spent grazing. Two hr/d were spent grazing for every km of travel during the
four grazing periods. 1S1H cows traveled less (P<.05) than HH, AH and 3S1H cows. Breed type means
were 5.0, 4.8, 4.1 and 4.8 km/d for HH, AH, 1S1H and 321H cows, respectively. The overall
distribution mean was 103 ha/cow (47 observations). Breed type was not significant in explaining the
variation in distribution of grazing. Breed type means were 105, 115, 93 and 99 ha/cow for HH, AH, 1
SIH and 3S1H cows, respectively. For every kg increase in CW (adjusted for cow condition),
distribution of grazing increased by .5 ha (P<.05). Also, for every ha increase in distribution of grazing,
cows gained .3 kg in body weight (P<.01>). GRAZING BEHAVIOR OF RANGELAND BEEF COWS
DIFFERING IN MILK PRODUCTION
by
W illia m James L a th ro p
A t h e s is s u b m itte d i n p a r t i a l f u l f i l l m e n t
o f th e re q u ir e m e n ts f o r th e deg re e
of
M a s te r o f S c ie n c e
in
A n im a l S c ie n c e
MONTANA STATE UNIVERSITY
Bozeman, Montana
December 1985
L 348'
ii
APPROVAL
o f a t h e s is s u b m itte d by
W illia m James L a th ro p
T h is t h e s is has been re a d by each member o f th e t h e s is c o m m itte e
a n d h a s b ee n f o u n d t o be s a t i s f a c t o r y r e g a r d in g c o n t e n t , E n g lis h
usage, f o r m a t, c i t a t i o n s , b ib lio g r a p h ic s t y l e , and c o n s is te n c y , and i s
re a d y f o r s u b m is s io n t o th e C o lle g e o f G ra d u a te S tu d ie s .
LU±J±t_______
1Le
_a) D /W»—
C h a irp e rs o n , G ra d u a te C om m itte e
A pproved f o r th e M a jo r D epartm ent
____
Date
Head, M a jo r D e p artm en t
A pproved f o r th e C o lle g e o f G ra d u a te S tu d ie s
/% ^ sr
D ate
" T s—
G ra d u a te Dean
iii
(
STATEMENT OF PERMISSION TO USE
In
p r e s e n tin g
th is
th e s is
in
p a r tia l
fu lfillm e n t
o f' th e
r e q u ir e m e n t s f o r a m a s t e r 's d e g re e a t M o n ta n a S t a t e U n i v e r s i t y ,
a g re e t h a t th e l i b r a r y
r u le s o f th e l i b r a r y .
s h a l l m ake i t
a v a ila b le to
B r i e f q u o t a t io n s fro m
w it h o u t s p e c ia l p e r m is s io n ,
I
b o rro w e rs under
t h i s t h e s is a re a llo w a b le
p ro v id e d t h a t a c c u r a te a ckn o w le d g e m e n t o f
s o u rc e i s made.
P e r m is s io n f o r
e x te n s iv e q u o t a t io n fro m
t h e s is may be g ra n te d by my m a jo r p r o fe s s o r ,
o r r e p r o d u c tio n
o r i n h i s absence,
D ir e c t o r o f L ib r a r ie s w hen, i n th e o p in io n o f e it h e r ,
o f th is
by th e
th e p roposed use
o f t h e m a t e r i a l i s f o r s c h o l a r l y p u r p o s e s . Any c o p y in g o r use o f th e
m a te r ia l
in
th is
w it h o u t my w r i t t e n
D ate
th e s is
fo r
p e r m is s io n .
f in a n c ia l
g a in
s h a l l n o t be a llo w e d
iv
ACKNOWLEDGEMENTS
d u r in g th e
a t t im e s ,
f in is h ,
p a s t fe w
seem ed t o
y e a rs , I
have a tte m p te d t o
be an i m p o s s i b l e
ta s k .
From
a c c o m p lis h w h a t,
th e
s ta rt
to
th e
e a ch day h a s b r o u g h t a new m e a n in g t o t h e w o rd f r u s t r a t i o n .
T h a n k s t o s e v e r a l p e o p le , I can now l o o k b a c k a t t h e e x p e r ie n c e a nd
f e e l a sense o f a c c o m p lis h m e n t.
To Don K r e s s ,
th a n k s f o r
a c h ie v e
K r i s H a v s ta d ,
p r o v id in g
my g o a l.
I
th e
hope
m o ra l
you a re
P e te B u r f e n in g a n d Dan D o o rn b o s ,
s u p p o rt
and g u id a n c e
I
needed t o
p le a s e d w it h my p e rfo rm a n c e as a
g ra d u a te s t u d e n t .
To S te v e Kachman and K a th y H a n fo rd ,
th e m a iz e o f c o n fu s io n a s s o c ia te d w it h
made i t
s ta tis tic s .
I
n e v e r w o u ld have
w it h o u t y o u r h e lp .
To my f e l lo w
s h a re d .
th a n k s f o r le a d in g me th ro u g h
g ra d u a te s tu d e n ts ,
th a n k y o u f o r th e
good tim e s we
These m em ories w i l l n e v e r be f o r g o t t e n .
To M a tt Wagner,
my re s e a rc h p a r tn e r and p e rs o n a l f r ie n d ,
h a v e n e v e r m ade i t w i t h o u t y o u r h e l p .
h o u r s y o u s p e n t on t h i s
I w o u ld
I th a n k y o u f o r th e c o u n t le s s
p r o je c t and y o u r u p l i f t i n g
sense o f hum or
h e lp e d me t h r o u g h tw o s u m m e rs i n H a v re .
M ost im p o r t a n t ,
I needed yo u .
to my w if e K a th y ,
They sa y t h a t
th a n k yo u f o r b e in g t h e r e when
b e h in d e v e r y s u c c e s s f u l man i s
woman. I s h o u ld go f a r because I have th e b e s t.
a good
TABLE OF CONTENTS
Page
L IS T OF T A B LE S ................................................................................................................... .......
L IS T OF F IG U R E S .............................................. .....................................................................
A B S T R A C T .............................................................................................................................. . v i i i
INTRODUCTION ........................................................................................................................
1
LITERATURE R E V IE W .......................................................................................................... .....
E nergy R e q u ire d F o r M a in t e n a n c e .................................................................
It
F o ra g e Q u a n tity and Q u a lit y
..........................................................................
6
C lim a te In f lu e n c e s .................................................................................................
IO
A n im a l F e a t u r e s .......................................................................... ...........................11
P h y s ic a l E n viro n m e n t . .............................................................................................. 3
MATERIALS AND M E TH O D S ......................
S t a t i s t i c a l A n a l y s i s .......................
RESULTS AND DISCUSSIO N...............................................
17
21
24
D a ily G ra z in g H o u r s ..................................................................................................27
Time o f Day G r a z i n g .................................................................................................. 33
D is ta n c e T ra v e le d
...................
41
D i s t r i b u t i o n o f G r a z i n g ..................................................................... ' . . .
43
S p e c u la tio n and F u tu re D ir e c t io n ................................................... . . .
46
S U M M ARY...................' ..................... .... .................................................................................. 50
LITERATURE CITED ...............................................................................................................
APP E N D IX ........................................................" ............................. . . .................................60
53
vi
L IS T OF TABLES
Tafale
Page
1.
O b s e rv a tio n p e r io d s and d a te s ............................................................ ....
2.
L e a s t-s q u a re s a n a ly s e s o f v a r ia n c e f o r cow body
w e ig h t, m ilk p r o d u c tio n and c a l f w e i g h t ..........................................25
3.
L e a s t-s q u a re s means and s ta n d a rd e r r o r s f o r cow body
w e ig h t , m ilk p r o d u c tio n and c a l f w e i g h t .............................................26
4.
L e a s t-s q u a re s a n a ly s is o f v a ria n c e f o r d a i l y g r a z in g
h o u rs ..............................................................................................................................28
5.
L e a s t-s q u a re means and s ta n d a rd e r r o r s f o r d a i l y
g r a z in g h o u rs o f th e i n t e r a c t i o n between b re e d and
p e r io d ( g r o u p ) ...................................................................................................... 31
6.
E f f e c t s o f c o v a r ia t e s on d a i ly g r a z in g h o u rs
7•
L e a s t-s q u a re s a n a ly s e s o f v a r ia n c e f o r tim e o f day
g r a z in g (2 4 00 -1 2 00 h r )
................................................................................. '34
8.
L e a s t-s q u a re s a n a ly s e s o f v a r ia n c e f o r tim e o f day
g r a z in g (12 00 -2 4 00 h r )
............................................................................... 35
9.
L e a s t-s q u a re s means f o r tim e o f day g r a z i n g ....................................... . 3 7
10.
. 20
................................. 32
L e a s t-s q u a re s means f o r tim e o f . day g r a z in g
( 0300-0600 and 1800-2100 h r ) f o r th e i n t e r a c t i o n
between b re e d ty p e and p e r io d ( g r o u p )
..............................................
39
11.
L e a s t-s q u a re s , a n a ly s is o f v a r ia n c e f o r d is ta n c e
t r a v e l e d ............................................................................................................... ....
1 2.
L e a s t-s q u a re s a n a ly s is o f v a r ia n c e f o r d i s t r i b u t i o n
o f g r a z i n g ............................................................................................................. 44
13.
R e s id u a l c o r r e la t io n s betw een g r a z in g b e h a v io r
v a r ia b l e s and cow and c a l f t r a i t s ...........................................................6 1
1 4.
R e s id u a l c o r r e la t io n s betw een d a i l y g r a z in g h o u rs
and tim e o f day g r a z i n g .........................................................
62
L IS T OF FIGURES
F ig u re
Page
1.
Map o f p a s t u r e ................................................................................... ....
2.
O v e r a ll tim e o f day
18
/
g r a z in g m e a n s ............................................................36
v iii
ABSTRACT
I t was th e p urpo se o f t h i s s tu d y t o
e v a lu a te th e
d if f e r e n c e s i n
g r a z in g b e h a v io r among s t r a i g h t H e re fo r d (HH), 50% Angus-50% H e re fo rd
(AH), 50% S im m ental-50% H e re fo rd (1S1H) and 75% S im m e n tal-25 % H e re fo rd
(3S1H ) l a c t a t i n g c o w s . A t o t a l o f 48 c o w s w e re d i v i d e d i n t o tw o
g r o u p s , e a c h g ro u p c o n t a i n i n g s i x co w s f r o m e a ch o f t h e f o u r b re e d
t y p e s . The s t u d y c o n s i s t e d o f f o u r I 0 - d g r a z in g p e r io d s s t a r t i n g on
J u ly 22 and e n d in g on A u g u s t 30. Cow w e ig h t (BW), c a l f w e ig h t (CW) and
m i l k p r o d u c t i o n (MP) e s t i m a t e s w e re t a k e n p r i o r t o p e r io d s I and 4.,
Cow c o n d i t i o n w a s e s t i m a t e d u s in g t h e w e i g h t / h e i g h t r a t i o a nd t h e
a v e r a g e c a l f age w as 105 d a y s ( r a n g e , 85 t o 124 d a y s ) . Cows ro a m e d
f r e e l y i n a 320 h a p a s t u r e w i t h s lo p e s r a n g in g f r o m 5 t o 40%.
V ib r a c o r d e r s and p e d o m e te rs w e re used t o e s tim a te t im e s p e n t g r a z in g
and d is ta n c e t r a v e le d , r e s p e c t iv e ly . D u rin g p e r io d s I , 2 and 4, th e 48
s tu d y cows w e re lo c a te d on a d a i l y b a s is b e tw e e n 600-900 h r by th e use
o f an a e r i a l p h o to map. From th e re c o rd e d lo c a t io n s , d i s t r i b u t i o n o f
g r a z in g w a s c a l c u l a t e d f o r e a ch co w . The o v e r a l l d a i l y g r a z in g mean
was 9.4 h r / d (633 o b s e r v a tio n s ) . No s i g n i f i c a n t b re e d ty p e d if f e r e n c e s
w e re fo u n d i n d a i ly g r a z in g h o u rs . B reed ty p e means w e re 9 .2 , 9.6, 9.2
a n d 9 .3 h r / d f o r HE, AH, IS IH a nd 3S1H c o w s , r e s p e c t i v e l y .
D a ily
g r a z in g h o u r s in c r e a s e d f r o m 8.0 h r / d i n p e r io d I t o 10.0 h r / d i n
p e r io d 4 . Of th e cow a nd c a l f t r a i t s u s e d as c o v a r i a t e s , o n ly MP a nd
c a l f age h a d a n y s i g n i f i c a n t e f f e c t s on t i m e s p e n t g r a z in g . The
p a r t i a l r e g r e s s io n c o e f f i c i e n t s f o r MP and c a l f age w e re .05 h r / d / k g / d
a n d - . 0 2 h r / d / d , r e s p e c t i v e l y ( a d ju s t e d f o r BW). The in c r e a s e i n
g r a z in g tim e due t o in c r e a s e d MP was m a in ly betw e e n 2 400-300 h r. The
o v e r a l l d is t a n c e t r a v e l e d m ean w a s 4 .7 k m /d (82 o b s e r v a t io n s ) a nd
f o l l o w e d th e same t r e n d a s t im e s p e n t g r a z in g . Two h r / d w e re s p e n t
g r a z in g f o r e v e ry km o f t r a v e l d u r in g th e f o u r g r a z in g p e r io d s . IS IH
cows t r a v e le d le s s (P<.05) th a n HH, AH and 3S1H cows. B re e d ty p e means
w e re 5 .0 , 4 .8 , 4.1 and 4 .8 k m /d f o r HH, AH, IS IH and 3S1H co w s ,
r e s p e c t i v e l y . The o v e r a l l d i s t r i b u t i o n mean w a s 103 h a /c o w (47
o b s e r v a t i o n s ) . B re e d t y p e w as n o t s i g n i f i c a n t i n e x p l a i n i n g t h e
v a r i a t i o n i n d i s t r i b u t i o n o f g r a z in g . B re e d ty p e means w e re 105, 115,
93 and 99 h a /c o w f o r HH, AH, I SI H a nd 3 8 1 H c o w s , r e s p e c t i v e l y . F o r
e v e ry k g in c r e a s e i n CW ( a d ju s te d f o r cow c o n d it io n ) , d i s t r i b u t i o n o f
g r a z in g in c r e a s e d by .5 h a (P C .0 5 ) . A ls o , f o r e v e r y h a in c r e a s e i n
d i s t r i b u t i o n o f g r a z in g , cows g a in e d .3 k g i n body w e ig h t (PC.OI).
I
INTRODUCTION
The ra n g e a n im a l g r a z e s o v e r a v a r i e t y
o f p la n t
G ra z in g on any p la n t co m m u n ity w i l l o f t e n r e s u l t i n
c e r t a in p r e f e r r e d p la n t s p e c ie s and p la n t p a r ts
197 8) .
T h is
fo r a g e
s e le c tiv e
th e s e le c t io n o f
(A rn o ld and D u d z in s k i,
p r o c e s s n o t o n l y a f f e c t s t h e c o m p o s it io n o f
co n su m e d b u t a ls o
a v a ila b le .to
c o m m u n it ie s .
th e
q u a n tity
and q u a l i t y
t h e a n im a l. As a r e s u l t o f t h i s
of
th e
fo ra g e
s e le c t iv e n a tu re ,
th e
fr e e - r o a m in g a n im a l spends m ore tim e e a t in g and f o r a g in g f o r fo o d th a n
th e
c o n f in e d
a n im a l.
T h is
e x tr a
m u s c u la r
a c tiv ity
c o n s id e r a b le im p a c t upon th e a n im a l’ s m a in te n a n c e
( O s u ji,
1974).
It
Y oung a n d C o r b e t t ,
th e
w o rk o f
m a t e r ia ls .
a
e n e rg y r e q u ir e m e n t
th e
c o n fin e d a n im a l (Graham ,
1964;
I 9 7 2 ; H a v s ta d a nd M a le c h e c k , I 9 8 2 ). O s u j i (1 9 7 4 )
s u g g e s te d t h a t th e in c r e a s e i n
due t o
have
has been e s tim a te d t h a t th e g r a z in g a n im a l r e q u ir e s
40 to 70% more d ie t a r y e n e rg y th a n th e
p r o b a b ly
ca n
e n e rg y
d ig e s tio n
th e a n im a l's m a in te n a n c e re q u ir e m e n t i s
c o s ts a s s o c ia te d w it h
done by
C o n v e n tio n a l
th e
g u t in
e s tim a te s
of
e a tin g ,
h a n d lin g
th e
w a lk in g and
b u lk y
e n e rg y
p a s tu re
r e q u ir e d
m a in te n a n c e have been made w it h a n im a ls housed in d o o r s i n
fo r
r e s p ir a t io n
cham bers. I n o rd e r t o m eet th e ra n g e a n im a l’ s m a in te n a n c e r e q u ir e m e n t,
l i v e s t o c k p r o d u c e r s n e e d t o a c c o u n t f o r th e a d d e d c o s t s a s s o c ia t e d
w it h
th e a n im a l's a c t i v i t i e s a t p a s tu re .
The e n e r g y c o s t o f e a t i n g h a s b e e n e s t i m a t e d t o
0 .8 3
be f r o m
0 .2 6 t o ,
k c a l / k g / h r ( O s u j i , I 9 7 4 ). A r n o ld a n d D u d z in s k i (.1978) r e v ie w e d
th e l i t e r a t u r e
a n d r e p o r t e d g r a z in g t im e s r a n g in g f r o m 5 t o 13 h r / d
2
w ith
th e
m a jo r it y
of
e s tim a te s
b e in g
b e tw e e n
9 to
10 h r / d . . The
e n e r g e t i c c o s t o f t r a v e l o n l e v e l t e r r a i n h a s b ee n e s t i m a t e d t o be
fro m
0 .4 5 t o
1974) w i t h
0 .7 8 k c a l / k g / k m
th e
( B la x te r ,
1 9 6 2 ; G ra h a m ,
c o s t o f a s c e n t b e in g te n
1964;
tim e s as c o s t l y
O suj i ,
(C la p p e rto n ,
I 9 6 4 ). C a t t l e h a v e b e e n e s t i m a t e d t o t r a v e l d is t a n c e s up t o 14 k m /d
(H e rb e l and N e ls o n ,
•
Under
I 9 6 6 ).
e x te n s iv e
ra n g e
c o n d itio n s ,
th e
in c r e a s e
in
e x p e n d itu r e c o u ld be even g r e a t e r . R a n g e la n d s o f t e n e x h i b i t
c o m b in a tio n s
d is tr ib u tio n .
of
v e g e ta tiv e
U n ifo rm
c o m m u n it ie s ,
d is tr ib u tio n
to p o g ra p h y
o f g r a z in g i s
d iffic u lt
e n e rg y
c o m p le x
and w a t e r
t o a c h ie v e
and la r g e a re a s o f th e ra n g e go u ng ra ze d w h ile o th e r a re a s a re s e v e rI y
o v e rg ra z e d .
over
A n im a ls may be fo r c e d
ro u g h
ra n g e la n d
te r r a in ,
can
in
to
s e a rc h
be d e t r im e n t a l
to
of
t r a v e l lo n g d is ta n c e s ,
fo o d
and w a te r .
b o th fo r a g e
p o s s ib ly
U neven use
and a n im a l
of
p r o d u c t iv it y
( A r n o ld and D u d z in s k i, I 9 7 8 ).
To m o re f u l l y
c o m p le t e
e s s e n tia l.
e x p l o i t a n im a l p r o d u c t i o n on r a n g e la n d s ,
u n d e r s t a n d in g
of
th e
a n i m a l 's
The m a jo r e m p h a s is o f t h i s
g r a z in g b e h a v io r o f f o u r g e n o t y p ic a lly
( s tr a ig h t
H e re fo rd ,
50%
A n g u s - 50%
f e e d in g
s tu d y
w as
a m o re
a c tiv itie s
to
is
e v a lu a t e t h e
d i f f e r e n t ty p e s o f b e e f c a t t l e
H e re fo rd ,
50%
S im m e n ta l-5 0 %
H e re fo r d , 75% S im m e n tal-25 % H e re fo r d ) g r a z in g ra n g e la n d . P a st re s e a rc h
has shown th e s e f o u r b re e d ty p e s t o be d i f f e r e n t i n fo r a g e c o n s u m p tio n
( K ro n b e rg
et
a l.,
( C a s e b o lt e t a l . ,
1983;
I 9 8 4 ),
W a g ne r
et
a l.,
dam p e r fo r m a n c e
1 9 8 5 ),
m ilk
and o v e r a l l p r o d u c t i v i t y
( K r e s s e t a l . 1 9 8 4 b ) a nd c a l f p e r fo r m a n c e ( K r e s s e t a l . ,
e t a l.,
1 9 8 5 ). The s p e c i f i c
o b je c tiv e s
p r o d u c t io n
1 9 8 4 b ; K re s s
w e re t o q u a n t i f y
/
t h e m a jo r
3
f r e e - r o a m in g d iu r n a l a c t i v i t i e s
g r a z in g ) ,
c h a r a c te r iz e
r e la t io n s h ip
( d is t a n c e t r a v e l e d a n d t i m e s p e n t
d is tr ib u tio n
of
g r a z in g
and e s tim a te
betw een a n im a l g r a z in g b e h a v io r and a n im a l p r o d u c tio n .
th e
/
4
LITERATURE REVIEW
G ra z in g i s
s ta n d in g ,
e a t in g and b o th h o r iz o n t a l and v e r t i c a l
can be d e f in e d
G r a z in g
th e a c t o f f o r a g in g f o r fo o d and th e p ro c e s s in v o lv e s
as
th e
b e h a v io r i s
re s p o n s e
of
a n a n im a l
c o n c e rn e d w i t h
movement.
to
its
B e h a v io r
e n v ir o n m e n t .
how t h e p r o c e s s o f g r a z in g i s
a f f e c t e d by th e e n v iro n m e n t i n w h ic h th e a n im a l f i n d s i t s e l f .
The f o c u s o f t h i s l i t e r a t u r e r e v ie w i s on t h e e n e r g e t i c c o s t o f
th e g r a z in g p ro c e s s t o
th e a n im a l and th o s e a n im a l and e n v iro n m e n ta l
f a c t o r s t h a t in f lu e n c e
th e deg re e o f e n e rg y b e in g expended.
E nergy R e g u ire d F o r Main te n a n c e
The e n e rg y r e q u ir e d f o r m a in te n a n c e (NEm) can be d e fin e d as t h a t
am o un t o f fe e d e n e rg y t h a t w i l l r e s u l t i n
e n e rg y a n d i s
p r o d u c t io n
is
th e
no l o s s
a m o u n t o f e n e rg y e q u i v a l e n t t o
o r g a in i n
th e f a s t in g h e a t
(N.RC, 1 9 8 4 ). The h e a t p ro d u c e d u n d e r f a s t i n g
p r o p o r t io n a l
to
th e
a n im a l's m e t a b o lic
ra te
body
w h ic h
c o n d itio n s
in c r e a s e s w it h
in c r e a s in g body s iz e . K le ib e r (1965) e s tim a te d t h a t body s iz e was m o st
a c c u r a t e ly
e x p re s s e d as body w e ig h t r a is e d
( 1962) re v ie w e d th e l i t e r a t u r e
c a ttle
h a v e on t h e
C u r r e n tly ,
k c a l/k g
a v e ra g e
L o fg re e n and G a r r e t t
th e .75 pow er.
B la x t e r
on m e t a b o lic r a t e and fo u n d t h a t a d u lt
a m e ta b o lic
t h e N a t i o n a l R e s e a rc h
BW*75 as t h e
to
m e t a b o lic
ra te
o f 81 k c a l / k g
C o u n c il (NRC,' 1 98 4 ) i s
ra te
fo r
c a ttle
BW’ ^S .
u s in g
77
as e s t a b l i s h e d
by
(1 9 6 8 ).
The m a in te n a n c e r e q u ir e m e n t i s
m o s t a p p l i c a b l e f o r a n im a ls i n
5
n o n s t r e s s f u l e n v iro n m e n ts w it h m in im a l a c t i v i t y .
a n im a l,
th e
m a in te n a n c e re q u ir e m e n t in c lu d e s
a s s o c ia te d w it h
e a tin g ,
w a lk in g ,
F o r th e f r e e —ro a m in g
th e
added e n e rg y
w o rk o f d ig e s t io n
t h e r m o r e g u l a t i o n . H a v s ta d a n d M a le c h e k
( O s u ji,
(1 9 8 2 ) r e p o r t e d
c o s ts
1974) and
an e n e rg y
e x p e n d i t u r e o f 16 I k c a l / k g B W *7 5 /d a y f o r f r e e - r a n g i n g h e i f e r s . T h is
was 46% g r e a t e r th a n th e 110 k c a l/ k g BW 75Zday e s tim a te d f o r s t a l l - f e d
h e ife r s .
F o r g r a z in g sheep,
in c re a s e s i n
e n e rg y e x p e n d itu r e o f 30% t o
70% have been, r e p o r te d (Young and C o r b e t t ,
1972; O s u ji,
1 9 7 4 ).
The e n e rg y c o s t o f m e re ly s ta n d in g h a s been e s tim a te d t o be fro m
0 .0 6
to
0 .3 8
k c a l/k g /h r
( O s u ji,
e s tim a te d a 12% in c r e a s e i n
1 9 7 4 ).
W e b s te r
and
V a lk s
(1 966)
e n e rg y e x p e n d itu r e o f s ta n d in g o v e r ly in g .
D epending on th e ty p e o f d i e t and th e m e a s u rin g te c h n iq u e s
used,
th e
e n e r g e t i c c o s t o f e a t i n g h a s b e e n e s t i m a t e d t o be f r o m 0.26 t o 0.83
k c a l/k g /h r
( O s u ji,
1 9 7 4 ).
G raham
(1 9 6 4 ) r e p o r t e d
a v a lu e
o f 0 .5 4
k c a l / k g / h r f o r sh e e p c o n s u m in g a ro u g h a g e d i e t a nd t h e c o s t w a s t h e
same w h e th e r th e m e a l was c u t o r u n c u t.
e n e r g e tic
cost
to
h a r v e s tin g
c o n c lu d e d t h a t th e
changes i n
th e
T h is assum es t h a t th e r e i s
fo ra g e ,
how ever
e n e rg y e x p e n d itu r e
Y oung
no
(1 9 6 6 )
d u r in g e a t in g w ere
due t o p r e h e n s io n a n d m a s t i c a t i o n . H o lm e s (1 9 7 8 ) o b s e r v e d s i m i l i a r
v a lu e s w it h
c a tt le
co n su m in g c u t p a s tu re b u t o b s e rv e d a mean v a lu e o f
0.67 k c a l / k g / h r f o r
in c lu d e s
c a ttle
h o r iz o n ta l
m e a s u re m e n t o f
th e
g r a z in g on s ta n d in g c ro p .
m ovem ent
e n e rg y
and
p r o b a b ly
c o s t o f g r a z in g .
is
The l a t t e r v a lu e
a
m o re
a c c u ra te
The e n e r g e t i c
cost o f
t r a v e l on l e v e l t e r r a i n has been e s tim a te d to be b e tw e e n 0.45 and 0.78
k c a l/k g /k m
C la p p e r t o n
( B la x t e r ,
(1 9 6 4 )
1962;
fo u n d
G ra h a m ,- 1964;
th e
e n e rg y
O s u ji,
cost
of
1974; R ib e ir o , 1977).
h o r iz o n ta l
m ovem ent
i
6
in c re a s e d w it h
speed and th e c o s t o f a s c e n t was te n t im e s as c o s t ly as
t h a t on l e v e l
t e r r a in .
The p r o c e s s o f g r a z in g ca n be e x t r e m e l y
c o s tly
if
t h e a n im a l
s p e n d s a n a p p r e c ia b l e a m o u n t o f t im e on th e a c t i v i t y , e s p e c i a l l y i f
th e
a n im a l
tr a v e ls
la r g e
d is t a n c e s
in
th e
p ro c e s s .
The s i t u a t i o n
becomes even w o rs e when a n im a ls g ra z e on s te e p s lo p e s and t r a v e l lo n g
d is t a n c e s w h e n n o t g r a z in g . Such c o n d i t i o n s a r e t y p i c a l l y
many m o u n ta in ra n g e la n d s and, as a r e s u l t ,
fo u n d on
th e m a in te n a n c e re q u ir e m e n t
o f th e a n im a l g r a z in g ra n g e la n d c o u ld be e x tre m e ly h ig h .
F orage Q u a n t it y and Qu a l i t y
Two
o f t h e m o s t i m p o r t a n t e n v ir o n m e n t a l f a c t o r s i n f l u e n c i n g
a n im a l g r a z in g b e h a v io r a r e f o r a g e q u a n t i t y a nd q u a l i t y .
b e e n g e n e r a l a g re e m e n t t h a t c a t t l e
o th e r s and s e le c t l e a f in
p re fe re n c e
to
p r e f e r some p l a n t s p e c ie s o v e r
p r e f e r e n c e t o s te m and g r e e n m a t e r i a l i n
d ry m a t e r ia l.
The m a t e r ia l s e le c te d ,
m a t e r i a l f r o m w h ic h i t w a s s e le c t e d , i s
p h o s p h a te
T h e re h a s
and g ro s s e n e rg y
(A rn o ld ,
com pared w it h
th e
u s u a lly h ig h e r i n n it r o g e n ,
1964).
T h is
s e le c t i v e
n a tu re n o t
o n ly a f f e c t s th e c o m p o s it io n o f t h e f o r a g e consu m e d b u t a ls o h a s a
d i r e c t in f lu e n c e upon th e q u a n t it y and q u a l i t y
to
o f th e fo r a g e a v a ila b le
th e a n im a l.
The q u a n t i t y
o f fo r a g e
consumed ( in t a k e )
is
p r o p o r t io n a l
a m o u n t o f t im e s p e n t g r a z in g , th e b i t i n g r a t e a n d ; th e b i t e
to
th e
s iz e . The
i n t e r r e l a t i o n s h i p s b e tw e e n th e s e v a r ia b le s w i l l v a ry w it h th e p h y s ic a l
s tru c tu re
o f th e fo r a g e
1 9 7 8) a n d w i t h
s te m ).
T h e re i s
( b u lk ,
th e q u a lit y
d e n s it y , h e ig h t )
of
no s e t p a t t e r n
th e fo r a g e
(A r n o ld and D u d z in s k i,
(g re e n v s .
d ry ,
le a f vs.
o f a d ju s t m e n t t o m e e t a p a r t i c u l a r
7
in t a k e
le v e l u n d e r d i f f e r e n t fo r a g e c o n d itio n s .
fo r a g e q u a n t i t y
of
b it e
and q u a l i t y
and in c r e a s e s
d e c re a s e s ,
th e
b itin g
th e a n im a l d e c re a s e s th e
ra te
(C h a co n a nd S to b b s .,
H e n d r ic k s e n a n d M in s o n , 19 8 0 ). The s iz e
q u a n tity
o f le a f
W h itta k e r ,
(Chacon and S to b b s,
1970) and fo r a g e
o f b ite
1 976),
d e n s it y
I n g e n e r a l , as t h e
in f lu e n c in g
b ite
le a f/ h e ig h t
fo ra g e h e ig h t ( A lld e n and
( A r n o ld a n d D u d z in s k i,
s iz e o f c a t t l e
r a tio
w e re
on t r o p i c a l
S c a r n e c c h ia
et
a l.
1 985)
th e
a lo w
m a jo r
p a s tu re s .
in c r e a s e s as fo r a g e h e ig h t and a v a i l a b i l i t y
1 970;
1976;
ta k e n d e c re a s e s as
d e c re a s e s . S tob b s (1973) s t a t e d t h a t a h ig h fo r a g e d e n s it y ,
c o n t e n t a n d a h ig h
s iz e
1 97 8 )
stem
fa c to rs
The b i t i n g r a t e
( A lld e n a n d W h i t t a k e r ,
and q u a n t it y
of
le a f
(C h a co n a nd
S t o b b s , ' 1 9 7 6 ) d e c r e a s e s . U n i f o r m i t y o f v e g e t a t i o n c o u ld a ls o h a v e a
in flu e n c e
b itin g
on b i t i n g r a t e . S c a r n e c c h ia e t a l . (1 9 8 5 ) o b s e r v e d h ig h e r
r a t e s on p a s t u r e s w i t h
p a s tu re s w it h
u n ifo r m
fo ra g e d i s t r i b u t i o n
p a tc h y f o r a g e d i s t r i b u t i o n .
th a n on
They c o n c lu d e d t h a t lo w
b i t i n g r a t e s w e re a s s o c ia te d w it h an in c r e a s e i n
tim e
s p e n t s e a rc h in g
b e tw e e n b it e s .
The p ro d u c t o f b i t e
As th e am ount o f fo r a g e
ra te
is
at fir s t
a v a ila b ility
a n im a l
and b i t i n g
ra te is
p re s e n t b e g in s t o
u n a ffe c te d ;
1 9 7 8 ).
it s
fe e d
t h e n a s ta g e i s
a nd i n t a k e
in t a k e r a t e
d e c lin e
a p p a r e n tly im p o s e s l i m i t a t i o n s
ca n i n g e s t
D u d z in s k i,
s iz e
th e
a n im a ls in t a k e
re a c h e d when fo r a g e
on th e r a t e
ra te
d e c lin e s
a t w h ic h th e
( A r n o ld a nd
A lld e n a n d W h i t t a k e r (1 9 7 0 ) f o u n d t h a t
p a s tu r e s c o n t a in in g a m ix t u r e o f ry e g ra s s ,
( g /m in ) .
sh e e p on
b ro m e g ra ss and s u b te rra e a n
c lo v e r w e re a b le t o m a in t a in a c o n s ta n t r a t e o f in t a k e when th e fo r a g e
h e ig h t was
b etw e e n 36.7 and 7.7 cm, b u t when fo r a g e h e ig h t f e l l b e lo w
8
7.7 cm th e a n im a ls w e re u n a b le t o
by i n c r e a s i n g
If
b itin g
com pensate f o r re d u c e d s iz e o f b i t e
ra te .
in t a k e le v e ls a re t o be m a in ta in e d ,
th e a n im a l has t o in c re a s e
th e a m o u n t o f t im e s p e n t g r a z in g t o c o m p e n s a te f o r th e d e c r e a s e i n
i n t a k e r a t e . H a v s ta d e t a l .
(1 9 8 3 ) fo u n d t h a t on c r e s t e d w h e a t g r a s s
p a s tu re s , Angus h e i f e r s w e re a b le t o
am ount o f a v a ila b le fo r a g e
m a in t a in in t a k e le v e l s
when th e
d e cre a se d fro m 920 to 140 k g DM/ha.
On th e
same t y p e o f p a s t u r e , S c a r n e c c h ia e t a l . (1 9 8 5 ) f o u n d t h a t a s f o r a g e
a v a ila b ility
d e c re a s e d
fro m
919
g r a z in g
t im e
in c r e a s e d fr o m 6.3 t o 10.9 h r /d a y and b i t i n g r a t e in c r e a s e d fro m
37 t o
50 b i t e s / m i n .
D u r in g
th is
d iffe r e n c e
in t a k e
as fo ra g e
in
y ie ld in g p a s tu re s ,
a v a ila b ilitie s
o f in t a k e
same
to
1 44 k g
s tu d y ,
D M /h a ,
N a s t is
a v a ila b ility
(1 9 7 9 )
o b s e r v e d no
d e c r e a s e d . On h ig h e r
A lld e n a nd W h i t t a k e r (1 9 7 0 ) fo u n d t h a t a t f o r a g e
g r e a t e r th a n 3000 k g DM/ha,
o f g re e n m a t e r ia l w e re r e l a t i v e l y
b o th g r a z in g tim e and r a t e
c o n s ta n t. As th e amount o f
d r y m a t t e r f e l l f r o m 3000 t o 500 k g D M /h a , t h e r e w a s a r e d u c t i o n i n
th e r a t e
o f c o n s u m p tio n f r o m
30 t o 5 g / m in a nd a in c r e a s e i n
t im e
s p e n t g r a z in g fro m 6.7 t o 11.7 h r / d a y .
The l i m i t
fo ra g e
to
w h ic h
a v a ila b ility
t h e a n im a l c a n c o m p e n s a te f o r
ca n d e p e n d u p o n th e
A r n o ld a n d D u d z in s k i (1 9 7 8 ) r e v ie w e d
g r a z in g t im e s f o r
fa llin g
lim its
c a ttle
b e tw e e n 9 t o
th e
ra n g in g fr o m 5 t o
10 h r / d .
S to b b s
c o n d itio n
of
d e c r e a s in g
th e
a n im a l.
lit e r a t u r e
and r e p o r t e d
13 h r / d w i t h
th e m a jo r it y
(1 9 7 5 ) r e p o r t e d
t h a t f a tig u e
th e am ount o f tim e t h a t can be s p e n t g r a z in g t o a b o u t 12 h r/d a y
a nd t h e n u m b e r o f b i t e s r a r e l y e x c e e d s 3 6 ,0 0 0 / d a y . A n im a ls i n
c o n d i t i o n may n o t be a b le t o g ra z e a s lo n g a s t h o s e i n
poor
b e t t e r sh a p e
9
and a s a r e s u l t be f o r c e d t o in c r e a s e t h e i r i n t a k e r a t e . A r n o ld a n d
B i r r e l l ( I 9 7 7 ) f o u n d w hen f o r a g e a v a i l a b i l i t y
consumed a g r e a t e r am ount o f fo r a g e i n
w a s lo w ,
th in
sh e e p
t h e same am ount o f t im e as f a t
sheep by e a t in g 25% f a s t e r .
S in c e
in t a k e
a v a ila b ility
lim it e d
is
(A rn o ld ,
by g u t f i l l .
lim it e d
1964),
by
b o th
d ig e s t ib ility
and
th e maximum l e v e l o f c o m p e n s a tio n can be
S c a rn e c c h ia e t a l .
a v a i l a b i l i t y was a t i t s
fo ra g e
lo w e s t,
(1985) n o te d t h a t when fo r a g e
g r a z in g tim e was o n ly . 9.4%
le s s th a n
t h e p ro p o s e d , m a x im u n i n d i c a t e d by S to b b s a nd f o r a g e d i g e s t i b i l i t y
(35.3% IVOMD) was p r o b a b ily l i m i t i n g
The t im e
in t a k e
o f day g r a z in g ta k e s p la c e i s
and th u s g r a z in g
a ls o in f lu e n c e d by fo ra g e
r e s o u r c e . A r n o ld (1 9 6 2 ) f o u n d a s f o r a g e a v a i l a b i l i t y
num ber o f g r a z in g p e r io d s d e cre a se d fro m
tim e .
d e c re a s e d , th e
seven t o f o u r p e r day and th e
a v e ra g e le n g t h o f a g r a z in g p e r io d in c r e a s e d fro m I t o 2 .5 h r .
F orage q u a n t it y
tr a v e le d .
and q u a l i t y
The im p o r t a n c e
of
a ls o h a s a m a jo r a f f e c t on d is ta n c e
fo ra g e
d is ta n c e t r a v e le d was i l l u s t r a t e d
q u a lity
and
p a s tu re
s iz e
on
by A nderson and Kothm ann (1980) who
f o u n d t h a t c a t t l e w i l l t r a v e l g r e a t e r d is t a n c e s u n d e r a c o n t in u o u s
g r a z in g
g r a z in g
s y s te m
th a n
u n d e r a ■h i g h - i n t e n s i t y - l o w - f r e q u e n c y
syste m . H e if e r s
u nd e r th e H IL F system
t r a v e le d
(H IL F )
1.5 km /d le s s
th a n h e i f e r s u n d e r th e c o n tin u o u s s y s te m . Crude p r o t e in and d i g e s t i b l e
e n e r g y w e re common in d e p e n d e n t v a r i a b l e s t h a t w e re s i g n i f i c a n t i n
e x p la in in g th e v a r i a t i o n i n
W a lk e r e t a l .
a n im a l t r a v e l und e r b o th g r a z in g s yste m s.
( 1985) fo u n d d i f f e r e n t r e s u l t s w it h m a tu re
cows u n d e r a
s h o r t d u r a t io n g r a z in g syste m v e rs e s a c o n tin u o u s g r a z in g s y s te m . Cows
on t h e
s h o r t d u r a t io n
g r a z in g
s y s te m
te n d e d t o
w a lk f u r t h e r
th a n
10
cow s
on
a
c o n t in u o u s
g r a z in g
s y s te m .
Q u in n
a nd
H e rv e y
(1 9 7 0 )
c o n t r o lle d fo r a g e q u a n t it y by u s in g d i f f e r e n t s t o c k in g r a t e s and fo u n d
t h a t y e a r lin g
s te e r s tr a v e le d
s i g n i f i c a n t l y le s s on l i g h t l y
s to c k e d
p a s tu re s th a n s t e e r s on m o d e ra te and h e a vy s to c k e d p a s tu re s . Over a 15
hr
o b s e r v a t io n
p e r io d ,
s te e r s a v e ra g e d
2.4 km i n
p a s tu re s
g ra z e d
l i g h t l y a nd 3 .2 km i n p a s t u r e s g r a z e d m o d e r a te a n d h e a v y . They n o t e d
t h a t a lth o u g h th e d is ta n c e t r a v e le d b e tw e e n m o d e ra te and heavy s to c k e d
p a s tu re s was n o t d i f f e r e n t ,
an e n t i r e l y d i f f e r e n t m anner o f t r a v e l was
o b s e rv e d b etw e e n t h e tw o i n t e n s i t i e s .
The h ig h amount o f t r a v e l on th e
■ m o d e ra te ly s to c k e d p a s tu re was due t o a f a i l u r e
to g ra z e w h ile m o v in g
t o w a t e r o r f r o m one a r e a t o a n o t h e r , w h e re a s m o v e m e n t on t h e h e a v y
s to c k e d p a s tu re was m o s tly w h ile g r a z in g . Thus, th e d is ta n c e an a n im a l
tr a v e ls
ca n be a c o m b in a t io n o f m o v e m e n t w h i l e g r a z in g ,
m o ve m e n t
b e tw e e n g r a z in g a r e a s o r m o v e m e n t b e tw e e n w a t e r a nd g r a z in g a r e a s .
When w a t e r i s
account fo r
n o t r e a d ily
m ost o f
th e
a v a ila b le ,
d is t a n c e
t r a v e l t o a nd f r o m
tr a v e le d
( A r n o ld
w a t e r ca n
a n d D u d z in s k i, .
1 9 7 8 ).
C lim a te In f lu e n c e s
A n o th e r
b e h a v io r i s
im p o r ta n t
th e w e a th e r.
th e t o t a l d a i l y
h o t a n d h u m id
e n v ir o n m e n t a l
The tim e
g r a z in g t im e i s
c o n d itio n s .
fa c to r
in f lu e n c in g
g r a z in g
o f day t h a t g r a z in g ta k e s p la c e and
a f f e c t e d m o s tly by v e ry c o ld and v e r y
H ancock
(1 9 5 4 ) o b s e r v e d no
c o r r e la tio n
b e tw e e n te m p e r a tu r e and g r a z in g t im e when te m p e ra tu r e s ra n g e d fro m 10
t o 27 C. D w y e r (1 9 6 1 ) fo u n d t h a t w h e n t h e a v e ra g e d a i l y t e m p e r a t u r e
exceeded 30 C. f o r th e day, cows d id n o t spend as much t im e g r a z in g as
when th e a ve ra g e te m p e ra tu r e was lo w e r th a n 30 C.
M a le ch e k and S m ith
11
( 1 97 6 ) n o t e d t h a t d u r in g t h e w i n t e r m o n th s co w s a l t e r e d t h e i r d a i l y
b e h a v o r ia l r o u t in e s i n re s p o n s e to
g r a z in g
was
(te m p e ra tu re
changes i n
p o s itiv e ly
c o r r e la te d
ra n g e ,
to
-2 4
( 0 .6 5 )
5 C) a nd
ra n g e ,
.4
to
15 .5
k m /h r).
re p o r te d t h a t p r e c ip it a t io n ,
w ith
a ir
b a r o m e t r ic
D is ta n c e t r a v e le d was n e g a t iv e ly c o r r e la t e d
( v e lo c ity
th e w e a th e r.
Time s p e n t
te m p e ra tu re
p re s s u re
( 0 .5 6 ) ,
(-0 .9 0 ) w it h w in d v e l o c i t y
A n d e rs o n a n d K o th m a n n
m a x im im
( 1 9 80)
d i u r n a l te m p e ra tu r e and v a p o r
p re s s u re
w e re i m p o r t a n t i n
tr a v e le d
u n d e r a h i g h - i n t e n s i t y - l o w - f r e q u e n c y (H IL F ) g r a z in g s y s te m .
From J u ly to December,
e x p la in in g
th e
a s th e te m p e ra tu r e
v a r ia tio n
in
d is t a n c e
d e cre a se d fr o m 35 t o - 3
C.,
d is t a n c e t r a v e l e d d e c r e a s e d f r o m 5 .5 t o 2.6 k m /d . I n G r e a t B r i t a i n ,
R u t t e r ( 1968) o b s e rv e d t h a t
c a ttle
c o v e r m ore g ro u n d w h ile g r a z in g i n
a r e m ore r e s t le s s ,
g ra z e
le s s and
c o ld , s to rm y o r w in d y w e a th e r.
Anim a l Fea tu r e s
M e a s u r a b le
changes in
g e n o ty p e and p h y s io lo g ic a l
in t a k e
le v e ls ,
g r a z in g
s ta te
a s d e t e r m in e d
of
b e h a v io r have been a t t r i b u t e d t o '
th e
a n im a l.
by e n e rg y
A n im a ls w it h
dem and,
h ig h e r
s h o u ld e x p r e s s a
d i f f e r e n c e i n g r a z in g b e h a v io r w hen c o m p a re d t o a n im a ls w i t h lo w e r
in t a k e
le v e ls
( A r n o ld ,
1 9 7 5 ).
and C h a ro la is x Angus l a c t a t i n g
S tr ic k lin
cow s,
e t a l . ( 1 9 7 6 ) , u s in g A n g u s
fo u n d t h a t th e la r g e r C h a ro la is
x A ngus co w s s p e n t m o re t i m e g r a z in g i n b o th w i n t e r a rid su m m e r th a n
th e s m a lle r Angus cows. D u rin g th e summer m onths,- Angus cows s p e n t 8.5
h r/d
g r a z in g w h ile
th e C h a ro la is x Angus cows s p e n t 9.0 h r / d g r a z in g .
Cow w e ig h t was n o t s i g n i f i c a n t i n e x p la in in g th e v a r i a t i o n i n
d a y l ig h t
g r a z in g h o u rs
g r a z in g h o u rs .
but
The p a r t i a l
was s i g n i f i c a n t
c o r r e la t io n
in
e x p la in in g
d a i ly o r
n ig h t t im e
c o e f f i c i e n t betw e e n cow w e ig h t
12
and n ig h t g r a z in g was - 0.2 0 ,
in d ic a t in g
t h a t l i g h t e r cows s p e n t m ore
t im e g r a z in g a t n i g h t th a n d id h e a v ie r c o w s . O th e r r e s e a r c h e r s h a v e
a ls o
r e p o r te d
and t o t a l
a n o n s ig n if ic a n t
d a ily
The
g r a z in g h o u rs
e ffe c t
d o c u m e n te d
by
of
m ilk
s e v e ra l
r e la t io n s h ip
b etw e e n cow body
w e ig h t
(B rum by, 1959; S to b b s , 1970).
p r o d u c t io n
re s e a rc h e rs
on
g r a z in g
(H a n c o c k ,
tim e
1954;
has
A r n o ld
been
and
D u d z in s k i, 1 9 6 7 ; S to b b s , I 9 7 0 ). When c o m p a r in g l a c t a t i n g J e r s e y and
F r ie s ia n
c o w s , B ru n b y (1 9 5 9 ) f o u n d n o d i f f e r e n c e s i n
g r a z in g
t im e
b e tw e e n t h e tw o b re e d s w h e n m i l k p r o d u c t io n w a s h e l d c o n s t a n t . The
F r i e s i a n co w s d id h a v e a h i g h e r f e e d i n t a k e p e r kg., o f m i l k p ro d u c e d
th a n
th e
J e rs e y -,
but
th is
m a in te n a n c e r e q u ir e m e n t.
p ro d u c e rs t o
d iffe r e n c e
w as a t t r i b u t e d
have th e lo n g e s t
p e r io d s o f n ig h t t im e
in
g r a z in g t i m e n o te d by S t r i c k l i n
to
th e le v e l o f m ilk
Because
th e d if f e r e n c e s
p r o d u c t io n .
H e rb e l and N e ls o n (1966) fo u n d
t h a t H e r e f o r d co w s s p e n t m o re t im e g r a z in g ,
d is t a n c e
means (H e re fo rd ,
g ra z in g .
e t a l . ( 1976) c o u ld h a v e b e e n due
On a y e a r lo n g b a s is i n New M e x ic o ,
le s s
a la r g e r
S to b b s (1970) n o te d a te n d e n c y f o r h ig h m il k
o f th e im p o rta n c e o f m il k p r o d u c tio n on g r a z in g tim e ,
tr a v e le d
to
t h a n t h e S a n ta G e r t r u d i s c o w s . B re e d g r o u p
S a n ta G e r t r u d is ,
f o r t im e s p e n t g r a z i n g ;
le s s t im e w a l k i n g a n d
r e s p e c t iv e ly ) w e re 10.3 and 8.9 h r / d
1.6 and 2.9 h r / d f o r t im e s p e n t w a l k i n g ; a n d
7.8 and 12.5 km /d f o r d is ta n c e t r a v e le d . H e re fo rd cows s p e n t m ore tim e
g r a z in g a t n ig h t th a n S a n ta G e r t r u d is
cows.
Y ea te s and M u rra y (1966)
h a v e sh o w n t h a t S a n ta G e r t r u d i s c a t t l e a r e s u p e r i o r t o H e r e f o r d s i n
w a lk in g a b i l i t y .
S a n ta G e r t r u d i s h e i f e r s h a d s m a l l e r in c r e a s e s i n
r e c t a l te m p e ra tu re and r e s p ir a t io n r a t e
th a n d i d H e r e f o r d h e i f e r s
13
under
c o n d itio n s
of
fo rc e d
e x c e r c is e .
They
s u g g e s te d
th a t
th e
s u p e r i o r i t y o f t h e S a n ta G e r t r u d i s may be p a r t l y due. t o h ig h e r h e a t
t o le r a n c e
d u r in g e x e r c is e .
T h e re seem s t o
tim e
(S to b b s ,
n o te d t h i s
be no r e l a t i o n s h i p
b e tw e e n i n t a k e
and g r a z in g
1970; H e n d ric k s e n and M in s o n , 1980). K ro pp e t a l.
r e l a t i o n s h i p when i n v e s t i g a t i n g th e d if f e r e n c e s i n
t im e b e tw e e n H e r e f o r d , H o l s t e i n a n d H e r e f o r d x H o l s t e i n
h e ife r s .
th e
g ro u p
w it h
th e h ig h e s t
Brumby (1959) showed
in t a k e
g r a z in g
y e a r lin g
No d if f e r e n c e s w e re fo u n d b e tw e e n th e t h r e e b re e d g ro u p s and
b re e d
w e ig h t.
(1973)
g r a z in g
t im e
g a in e d
th e
le a s t
t h a t g r a z in g t im e r e q u ir e d p e r u n i t o f
was g r e a t e r f o r J e rs e y
cow s th a n f o r
F r ie s ia n
co w s. S in c e
g r a z in g t i m e and i n t a k e r a t e a r e b o t h m e a s u re m e n ts o f t h e e f f o r t o f
g r a z in g ,
c o u ld
th e d if f e r e n c e
p o s s ib ly
lie
b etw e e n a n im a ls w it h
in
th e
a re a
d e m o n s t r a te d t h a t s t r u c t u r a l l y
v o lu m e
th a n
s m a l l e r a n im a ls
l a r g e r ru m e n v o lu m e s t e n d t o
of
th in
in ta k e
ra te .
(N u tt
e t a l.,
1 9 7 7 ).
A r n o ld
has
been
198 0 ) a nd s h e e p w i t h
co n su m e f o o d f a s t e r
th a n
(1 9 7 5 ) d e m o n s t r a te d
l a c t a t i n g sheep a c h ie v e h ig h e r in t a k e le v e ls th a n
by in c r e a s in g
t h e i r in t a k e
ra te
and o n ly
g ra z e lo n g e r .
W h e th e r t h i s
r e la t io n s h ip
th a t
a
sh e e p w i t h
1966; W arner and S ta c y ,
sheep have been shown t o e a t f a s t e r th a n f a t
a nd B i r r e l l ,
It
le v e ls
l a r g e r a n im a ls h a v e a l a r g e r ru m e n
s m a lle r rum en v o lu m e s (P u rs e r and M o ir ,
A ls o ,
d i f f e r e n t in t a k e
1968).
sheep (A rn o ld
p r e g n a n t a nd
d ry sheep p r i m a r i l y
on a bu n d a n t p a s tu re do th e y
h o ld s
tru e
fo r
c a ttle
is
not
known.
£ h y s ic a l E n viro n m e n t
R a n g e la n d s o f t e n
e x h ib it
c o m p le x c o m b in a t io n s o f v e g e t a t i v e
14
com m u n it ie s ,
to p o g ra p h y
and w a te r d i s t r i b u t i o n .
Even d i s t r i b u t i o n
of
g r a z in g i s o ft e n d i f f i c u l t t o a c h ie v e and la r g e a re a s o f th e ra n g e may
go u n g ra z e d w h i l e o t h e r a r e a s a r e s e v e r e ly o v e r g r a z e d . As a r e s u l t ,
th e t o t a l a v a ila b le fo r a g e and t h a t fo r a g e a v a ila b le t o th e a n im a l may
d i f f e r . B e ca u se o f t h e im p o r t a n c e o f f o r a g e q u a n t i t y . a n d q u a l i t y on
g r a z in g tim e and d is ta n c e t r a v e le d ,
d is tr ib u tio n
o f g r a z in g becom es
an im p o r ta n t a s p e c t o f g r a z in g b e h a v io r .
Due t o
th e g r a z in g a n im a l's s e le c t iv e
c o m m u n itie s and p la n t
th e
d e g re e
of
u se
s p e c ie s
of
any
n a tu re ,
th e ty p e o f p la n t
p re s e n t can have a m a jo r in f lu e n c e
g iv e n
a re a .
C a ttle
e x h ib it
a
on
m a rk e d
p re fe re n c e f o r some p la n t c o m m u n itie s w h ile a v o id in g o th e r s ( Roath and
K ru e g e r,
th e y
1982). P re fe re n c e i s m a in ly f o r g ra s s e s b u t as g ra s s e s m a tu re
can be re p la c e d by f o r b e s and b ro w se (Cook and H a r r is ,
g e n e ra l, c a t t l e
The p h y s i c a l
p a la ta b le
u tiliz a tio n ,
In
p r e f e r to g ra z e th o s e a re a s i n w h ic h th e p r o p o r t io n o f
p a la t a b le and p r e fe r e d s p e c ie s i s
im p a c t on th e
1968) .
s tru c tu re
d is tr ib u tio n
s p e c ie s
had
a
of
g r e a t e s t ( M i l l e r and K ru e g e r,
th e
p a s tu re
o f g r a z in g .
p o s itiv e
1976).
ca n a ls o h a v e a m a jo r
Cook (1966) fo u n d t h a t p e rc e n t
a ffe c t
on
th e
b u t s e v e r a l o th e r f a c t o r s a p p e ared t o
d e g re e
of
a re a
be m ore im p o r t a n t .
S ix o u t o f t h e e le v e n m o s t i m p o r t a n t v a r i a b l e s w e re c o n c e rn e d w i t h
p e rc e n t s lo p e .
M u e g g le r d 965) fo u n d t h e r e t o be an i n t e r a c t i o n betw e e n
d is ta n c e u p s io p e and s lo p e s te e p n e s s . On a 10% s lo p e , w h e re a cce ss was
m a in ly fro m
th e b o tto m ,
75% o f c a t t l e
use is , l i k e l y
t o be w i t h i n
810
y a r d s o f t h e f o o t o f t h e s lo p e . On a 60% s lo p e , 75% o f u s e i s l i k e l y
to
be w i t h i n 35 y a rd s o f th e f o o t o f th e s lo p e .
S in c e
w a te r
is
e s s e n tia l
fo r
lif e ,
w a te r
a v a ila b ilit y
and
15
d is tr ib u tio n
d is tr ib u tio n .
v a lu e s
fo r
is
e x p e c te d
W h ile t h e r e i s
any
g iv e n
to
have
a m a jo r
im p a c t
c o n s id e r a b le v a r i a t i o n
d is t a n c e ,
th e re
is
a
on
g r a z in g
among u t i l i z a t i o n
c o n s is ta n t
tre n d
of
d e c re a s e d u t i l i z a t i o n
as th e d is ta n c e fr o m w a te r in c r e a s e s ( V a le n tin e ,
19 ^ 7 ) .
G ille n
(1 9 8 4 ) fo u n d t h a t on f o r e s t e d m o u n t a in r a n g e ,
c a ttle
p r e f e r r e d a re a s w i t h i n 200 m o f w a te r and a v o id e d a re a s g r e a t e r
th a n
e t a l.
600 m f r o m
w a te r.
On s i m i l a r r a n g e ,
R o a th and K r u e g e r (1 9 8 2 )
r e p o r te d z e ro u t i l i z a t i o n a t d is ta n c e s a ro u n d 1900 m fro m w a te r .
O th e r f a c t o r s t h a t may in f lu e n c e d i s t r i b u t i o n
aspect
of
d is t a n c e
s lo p e
fro m
( G o n z a le z ,
tr a ils
l o c a t i o n a nd b r u s h
a nd
1 9 6 4 ),
ro a d s
th ic k n e s s
s u rfa c e
(R o a th
(C o o k ,
o f g r a z in g in c lu d e
ro c k
and
( G ille n ,
K ru e g e r,
I 96 6 ) a nd t r e e
1 9 8 3 ),
19 8 2 ),
s a lt
c o v e r a nd dow n
t i m b e r ( H e d r ic k e t a l . 1968).
B e c a u s e o f t h e c o m p le x i n t e r a c t i o n s
b e tw e e n t h e m any f a c t o r s
i n f l u e n c i n g d i s t r i b u t i o n o f g r a z in g , no o ne f a c t o r can be u s e d a s a
r e lia b le
in d ic a to r in
p r e d ic tin g
th e
1983). U s in g 21 in d e p e n d e n t v a r ia b le s ,
use' o f any one a r e a ( G i l l e n ,
Cook (1966)
f o r b e tw e e n 50 t o 60% o f th e v a r i a t i o n i n
th e use o f m o u n ta in s lo p e s .
I t a p p e a rs t h a t p la n t co m m u n ity c h a r a c t e r i s t i c s ,
le n g t h
and w a te r
d is t r ib u t io n
a re
th e
d is tr ib u tio n
on m o u n ta in ra n g e s ( G ill e n ,
f e n c in g
s tr a te g ic
and
lo c a tio n s
fo r
c o u ld o n ly a c c o u n t
m a jo r
s lo p e
g r a d ie n t and
d e te r m in a n ts o f
1983).
m in e r a l
c a ttle
D e ve lo p m e n t o f w a te r ,
s u p p le m e n ts a r e
th e
p rim a ry , m ethods d ir e c t e d to w a rd s a l l e v i a t i n g th e s e p ro b le m s (Kothm ann,
1980) .
The e f f e c t o f t h e
p h y s i c a l e n v ir o n m e n t on t h e ra n g e a n i m a l ’ s
g r a z in g b e h a v io r h a s m o s t ly been c o n c e rn e d w i t h
d is t a n c e t r a v e l e d .
16
When fo r a g e q u a n t i t y and q u a l i t y
c a ttle
w ill
on p r e f e r r e d g r a z in g a re a s d e cre a se s,
t r a v e l f a r t h e r d is ta n c e s ,
p o s s ib ly o v e r ro u g h t e r r a i n ,
to
l e s s p r e f e r r e d a r e a s . When w a t e r i s n o t r e a d l y a v a i l a b l e , t r a v e l t o
and fro m w a te r can a c c o u n t f o r m o st o f
and D u d z in s k i,
(197 8) ,
fo u n d
19 78).
th a t
S c h m id t (1 9 6 9 ),
under
fre q u e n c y o f d r in k in g fro m
th e s e
th e
d is ta n c e
t r a v e le d
(A rn o ld
as c it e d by A rn o ld and D u d z in s k i
c o n d itio n s
c a ttle
may a l t e r
th e ir
one v i s i t t o w a t e r p e r d a y t o once e v e r y
o th e r day. He a ls o o b s e rv e d c a t t l e
s p littin g
up i n t o
g ro u p s ,
th o s e who
f o r a g e c lo s e t o w a t e r ( n o n w a lk e r s ) a nd t h o s e who h e a d f r o m w a t e r t o
d i s t a n t f e e d in g a r e a s ( w a lk e r s ) .
The o n l y d i s c e r n i b l e
d iffe r e n c e
b e tw e e n th e tw o g ro u p s was th e p r o p o r t io n o f cows w it h o u t c a lv e s ,
b e in g
1 9% i n
th e
n o n w a lk e r s a nd 39% i n
th e
w a lk e r s .
th is
The w a lk e r s
a v e ra g e d 16 km /d a y w h ile th e n o n w a lk e rs a ve ra g e d 9.6 k m /d a y.
The im p o rta n c e o f th e p h y s ic a l e n v iro n m e n t on tim e
s p e n t g r a z in g
i s n o t w e l l d o c u m e n te d . P e te r s o n a n d W o o lf o l k (1 9 5 5 ) o b s e r v e d lo w e r
g r a z in g
t im e s
s to c k e d p a s tu re .
on a m o d e r a t e ly
s to c k e d
They c o n c lu d e d t h a t i n
p a s tu re
th is
case,
th a n
th e s h o r te r g r a z in g
t im e on t h e m o d e r a t e ly s to c k e d p a s t u r e r e s u l t e d f r o m
to p o g ra p h y
p a s tu r e .
and v e g e t a t i o n
s u b ty p e s
th a n
on a l i g h t l y
on t h e
m o re u n if o r m
lig h tly
s to c k e d
17
MATERIALS AND METHODS
The s tu d y was c o n d u c te d d u r in g th e summer o f 1984 i n th e B e a r Paw
M o u n t a in s , 3 2 'km s o u t h e a s t o f H a v r e , M o n ta n a . The s t u d y s i t e h a d an
a v e ra g e e le v a t io n
4 5 .7
to
5 0 .8
cm.
o f 1300 m w it h
The
p a s tu re
an a n n u a l p r e c i p i t a t i o n ra n g in g fro m
used
fo r
th e
s tu d y
( fig u r e
I)
was
a p p r o x im a t e ly 320 ha i n s i z e and t h e t e r r a i n w as r u g g e d w i t h s lo p e s
r a n g in g fro m 5 t o 40%. A r e s e r v o ir and c re e k w e re th e o n ly s o u rc e s o f
a v a ila b le
w a te r.
A d is t a n c e
a r e a s . The p a s t u r e i s
of
1.6 km s e p a r a t e d t h e tw o w a t e r i n g
t r a d itio n a lly
s t o c k e d w i t h a p p r o x im a t e ly 250
l a c t a t i n g c o w s f r o m J u l y 21 t o S e p te m b e r I f o r a t o t a l o f 325 AU M’ s.
T h is can be c o n s id e r e d a s t o c k i n g r a t e
d o m in a te d
by ro u gh fe s c u e
(F e s tu c a
o f 1.0 h a/A U M . The p a s t u r e i s
s c a b r e lla ) ,
Id a h o fe s c u e
(F e s tu c a
i d ah o e n s is ) and b lu e b u n c h w h e a tg ra s s ( Ag ro p y ro n s p ic a t u m) w it h an open
p o n d e ro s a p in e ( P in u s g o n d e r p s a ) o v e r s t o r y . K e n tu c k y b lu e g r a s s (P oa
p r a t e n s is ) d o m in a te d th e lo w la n d v e g e t a t io n .
A t o t a l o f 48 cows w e re d iv id e d i n t o
c o n ta in in g
s ix cow s fro m
tw o g ro u p s w it h
each g ro u p
t h e f o l l o w i n g f o u r b re e d t y p e s ; s t r a i g h t
H e re fo r d (HH), 50% Angus-50% H e re fo rd (AH), 50% S im m ental-50% H e re fo rd
( I SI H) a nd 75% S im m e n ta l-2 5 % H e r e f o r d (3-SI H). The co w s u s e d i n
th is
s t u d y w e re b e tw e e n 5 and 8 y r o f age a nd s e le c t e d a t ra n d o m ( w i t h i n
b re e d ty p e ) fro m
th e
cow h e r d . A l l c o w s .w e re l a c t a t i n g
a nd f r o m
a
common management b a ckg ro u n d . C a lve s w e re s ir e d by e i t h e r C h a ro la is o r
T a r e n t a is e b u l l s . V i b r a c o r d e r s, as d e s c r ib e d by S to b b s (1 9 7 0 ), w e re
used t o
e s tim a te th e am ount o f tim e s p e n t g r a z in g .
Tim e s p e n t g r a z in g
18
Creek
R e s e rv o ir
F ig u r e I . Map o f p a s tu re
19
was d e te rm in e d
B o th d a i l y
by e s t im a t in g
g r a z in g a c t i v i t y
g r a z in g h o u rs and th e tim e
a n a ly z e d .
To e s t i m a t e t h e t i m e
g r a z in g t im e w a s d i v i d e d i n t o
to
th e n e a re s t .25 h r.
o f day g r a z in g to o k p la c e w e re
o f d a y g r a z in g o c c u r e d ,
e i g h t 3- h r t im e
0 3 0 0 -0 6 0 0 , 0 6 0 0 -0 9 0 0 , 0 9 0 0 -1 2 0 0 ,
p e r io d s
each d a y ’ s
(2400- 0300,
1 2 0 0 -1 5 0 0 , 1 5 0 0 -1 8 0 0 , 1 8 0 0 - 2 1 0 0 ,
2 1 0 0 -2 4 0 0 ).
P e d o m e te rs , a s d e s c r ib e d by A n d e rs o n a nd K o th m a n n ( 1 9 7 7 ) , w e re
used t o e s tim a te d is ta n c e t r a v e le d . Due t o th e v a r i a t i o n i n
o f s tr id e
d iv id in g
th e le n g t h
b e tw e e n a n im a ls , a c a l i b r a t i o n f a c t o r w a s c a l c u l a t e d by
th e t r a v e l d is ta n c e m easured on th e
p e d o m e te r by th e a c t u a l
d is ta n c e w a lk e d . F iv e cows (H e re fo rd ) w e re w a lk e d a d is ta n c e o f 1.6 km
to
d e t e r m in e
d e t e r m in e d
th e
c a lib r a tio n
by d i v i d i n g
th e
fa c to r.
D a ily
d is t a n c e
tr a v e le d
p e d o m e te r r e a d in g s by t h e
was
c a lib r a tio n
f a c t o r ( . 8 ) a n d t h e n a d j u s t i n g t h i s d is t a n c e t o a 2 4 - h r b a s is . Use o f
th e c a l i b r a t i o n f a c t o r a d ju s te d f o r d if f e r e n c e s i n le n g th o f s t r i d e
w i t h i n b r e e d t y p e , b u t d id n o t a d j u s t f o r d i f f e r e n c e s b e tw e e n b re e d
ty p e .
Due
to
p e d o m e te r s ,
th e
p o s s ib le
v a r ia tio n
in
a n im a ls w e re , r a n d o m ly a s s ig n e d
m e a s u re m e n ts
b e tw e e n
p e d o m e te r s each
t im e
e q u ip m e n t changes w e re made.
The o b s e r v a tio n d a te s a re shown i n
b e tw e e n t h e tw o g r o u p s o f co w s
f o u r 1 0 - d p e r io d s s t a r t i n g
w e ig h ts ,
to
I
and 4 .
e v e r y 10 - d . The s t u d y c o n s is t e d o f
on J u l y 22 and e n d in g on A u g u s t 3 0 . Cow
c a l f w e ig h ts and m il k
p e r io d s
t a b le I . E qu ip m e n t was r o t a t e d
p r o d u c tio n e s tim a te s w e re ta k e n p r i o r
A fte r a 7 h r.
s e p a r a t io n
tim e ,
cow
and c a l f
w e ig h ts w e re ta k e n and m il k p r o d u c tio n was e s tim a te d u s in g th e w e ig h s u c k le -w e ig h
te c h n iq u e
( W illia m s
e t a l.,
1979a).
M il k
p r o d u c tio n was
20
T a b le I .
O b s e rv a tio n p e r io d s and d a te s
Group
P e rio d
D ates
2
I
J u ly 22 - J u ly 3 1 *
T
2
Aug.
2
3
A ug. 11 - A ug. 20
I
4
I - Aug. 10
hi) I
I
‘
I
%I
I
<
hO
- I
cv 1
. I
5 I
I
I
Cow w e ig h ts , c a l f w e ig h ts and m il k p r o d u c tio n
e s tim a te s w e re ta k e n p r i o r t o th e s e p e r io d s .
t h e n c o n v e r t e d t o a 2 4 - h r b a s is by m u l t i p l y i n g t h e e s t i m a t e by 3 . 4 .
Cow m e t a b o lic b o d y w e ig h t (b o d y w e ig h t
w as c a l c u l a t e d b u t w a s
f o u n d t o be h i g h l y c o r r e l a t e d w i t h b o d y w e ig h t ( . 9 9 ) a nd n o t u se d i n
a n y a n a ly s e s .
r a tio
Cow c o n d i t i o n w a s e x p r e s s e d a s t h e w e ig h t t o h e i g h t
( W illia m s e t a l . ,
1979 b ; Dunn e t a l . ,
1983) and th e a verag e c a l f
a ge ( s t a g e o f l a c t a t i o n ) w a s I 05 d ( r a n g e = 85 t o I 24 d ) a t th e s t a r t
o f th e e x p e rim e n t.
G r a z in g d i s t r i b u t i o n
w a s m o n it o r e d
d u r in g g r a z in g p e r io d s I , 2
and 4. The 48 s tu d y cows w e re lo c a te d on a d a i l y b a s is betw een 600 and
900
h r.
g r a z in g
re c o rd e d
P r e lim in a r y
a c tiv ity .
on
c a lc u la te d
a n a ly s is
E ach
g r id d e d
fo r
e a ch
g r a z in g lo c a t io n s
r e v e le d
a n i m a l 's
a e r ia l
th is
lo c a tio n
p h o to
cow by f i n d i n g
and th e n c a lc u la t in g
m aps.
th e
to
be m a jo r p e r io d
w as
d e t e r m in e d
A g r a z in g
g e o g r a p h ic
c e n te r
g e o g ra p h ic c e n te r t o each i n d i v i d u a l o b s e r v a tio n as o u t lin e d
(1 9 4 9 ) a n d u s e d by G i l l e n
f r e e - r a n g in g
beef
cow s.
b y ■a n d
r a d iu s
th e a verag e d is ta n c e
of
was
of
th e
fro m
th e
by Hayne
( 19 83) t o e s t i m a t e t h e hom e ra n g e s i z e o f
The g r a z in g
r a d iu s
was
th e n
s q u a re d
a nd
I
21
m u ltip lie d
d is tr ib u tio n
by 3 .1 4 ( t h e a r e a o f a c i r c l e ) t o e s t i m a t e each a n i m a l’ s
o f g ra z in g .
U s in g c o m m e r ic a lly a v a ila b le s to c k dye, a l l cows w e re m arked w it h
la r g e
n um be rs t o
a id
p la c e d n e a r w a t e r
in
to
id e n t if ic a t io n .
m in im iz e
S m a ll
p o r ta b le
a n im a l d is t u r b a n c e
c o r r a ls
w e re
w h e n e q u ip m e n t
c h a n g e s w e re m ade. On d a y s w h e n e q u ip m e n t c h a n g e s w e re m ade, d a i l y
g r a z in g and t im e o f day g r a z in g d a ta w e re n o t used and a n im a l lo c a t io n
was n o t re c o rd e d .
d a ily
The p o s s ib le
g r a z in g h o u rs ,
was e ig h t ,
t im e
e ig h t and one,
num ber o f o b s e rv e t i o n s / c o w /p e rio d f o r
o f day g r a z in g h o u rs and d is ta n c e t r a v e le d
r e s p e c t iv e ly .
For d is t r ib u t io n
of
g r a z in g ,
o n ly one o b s e rv a tio n /c o w was re c o rd e d o v e r th e s tu d y p e r io d .
S t a t i s t i c a l A n a ly s is
D a ta w e re a n a ly z e d by l e a s t
s q u a r e s p ro c e d u re s and d if f e r e n c e s
b e tw e e n f a c t o r l e v e l means w e re t e s t e d u s in g LSD m ethods (SAS,
A l l n o n s i g n i f i c a n t tw o - w a y i n t e r a c t i o n s ,
a n a ly s e s ,
1982).
as re v e a le d by p r e lim in a r y
w e re rem oved t o a r r i v e a t th e f i n a l l i n e a r m o d els.
A m ix e d m o d e l w as e m p lo y e d f o r a n a l y s i s o f b o t h d a i l y g r a z in g
h o u r s a nd t im e o f d a y g r a z in g . The l i n e a r m a t h e m a t ic a l m o d e l w as as
fo llo w s :
Yi j k l m
j
= u + Bi + Gj + C( k ) i j + P( 1 ) j + D( m ) lj + BPi l j
+ ei j k l m ,
w here
I
Y ijk im = an o b s e r v a tio n
;
u = th e o v e r a ll mean,
Bi
= th e f i x e d e f f e c t o f th e i t h
Gj
= th e
f i x e d e f f e c t o f. th e j t h
b re e d ty p e ,
g ro u p ,
I
■
. i
!
|
22
C( k ) i j
P( l ) j
= t h e ra n d o m e f f e c t o f t h e k t h
w i t h i n th e j t h g ro u p ,
=
fix e d
e f f e c t o f th e I t h
D( m ) l j = t h e f i x e d
e ffe c t
w it h in j t h
BPi l j
th e i t h
p e r io d w i t h i n t h e j t h
o f t h e m th day w i t h i n
b re e d
g ro up ,
th e I t h
p e r io d '
g ro u p ,
= th e in t e r a c t io n
p e r io d w i t h i n
ei j k l m
cow w i t h i n
b e tw e e n t h e i t h
th e j t h
b re e d t y p e and t h e I t h
g ro u p ,
= random e r r o r .
B re ed ty p e and g ro u p w e re t e s t e d u s in g t h e random e f f e c t o f cow (breed
x
g r o u p ) a nd a l l
o th e r
e ffe c ts
w e re
te s te d
F o r a n a l y s i s o f d is t a n c e t r a v e l e d ,
u s in g b re e d ty p e ,
g ro u p ,
p e r io d (g ro u p ) ,
u s in g
th e
r e s id u a l.
a f i x e d m o d e l w as e m p lo y e d
se x o f c a l f and s ir e
breed o f
c a l f a s f i x e d m a in e f f e c t s . T w o -w a y i n t e r a c t i o n s in c lu d e d b re e d by
p e r io d (g ro u p ) and b re e d by s i r e
The m odel
used f o r
b re e d
d is tr ib u tio n
o f c a lf.
o f g r a z in g in c lu d e d
b re ed ty p e ,
s e x o f c a l f a n d s i r e b re e d o f c a l f a s f i x e d m a in e f f e c t s a n d no t w o way in t e r a c t io n s
w e re fo u n d t o be s i g n i f i c a n t ( P X 1 0 ) . B e ca u se t h e
n u m b e r o f o b s e r v a t io n s i n f l u e n c e s
( G ille n ,
1 9 8 3 ),
d is tr ib u tio n
th e
num ber
of
th e
s iz e
o f th e
o b s e r v a t io n s
o f g r a z in g w a s i n c l u d e d i n
e s t im a t e d a r e a
u se d
to
c a lc u la te
t h e m o d e l a s a c o n t in u o u s
in d e p e n d e n t v a r ia b l e .
R e a liz in g t h a t th e m echanism s in v o lv e d i n
th e
c o n t r o l o f e ne rg y
b a la n c e a r e p o o r ly u n d e r s t o o d ( B a i l e a n d F o r b e s , I 9 7 4 ), th e p o i n t o f
v ie w
t a k e n d u r in g t h i s
a n im a l i s
w e ig h t ,
a r e fle c tio n
s t u d y w as t h a t t h e b e h a v io r o f t h e g r a z in g
o f i t ’ s e n e r g y r e q u ir e m e n t . As a r e s u lt " , cow
cow m il k p r o d u c tio n and cow c o n d it io n ,
a lo n g w it h
c a l f w e ig h t
23
and c a l f age,
w e re used as c o v a r ia t e s w h e ne ve r p o s s ib le t o
t h e i r e f f e c t on d a i l y g r a z in g h o u r s ,
t im e o f day g r a z in g ,
d e te rm in e
d is t a n c e
t r a v e l e d a n d d i s t r i b u t i o n o f g r a z in g . F o r d a i l y g r a z in g a nd t im e o f
day
g r a z in g ,
c o w (b re e d
x g ro u p )
w a s re m o v e d f r o m
th e
m odel
and
r e p la c e d by s e x o f c a l f and s i r e b re e d o f c a l f . B e c a u s e t h e cow and
c a l f m ea surem e n ts w e re ta k e n p r i o r t o p e r io d s I and 4 ,
th e s e t r a i t s
on d a i l y
g r a z in g h o u r s ,
th e e f f e c t s
of
t im e o f day g r a z in g h o u r s and
d is ta n c e t r a v e le d a re o n ly d u r in g th e s e tw o p e r io d s . An average o f th e
m e a s u re m e n ts r e c o r d e d i n
p e r io d s
tr a its
d is tr ib u tio n
was
used
in
th e
o b s e rv a tio n /c o w f o r d i s t r i b u t i o n
I and 4 f o r a l l t h e cow and c a l f
m odel
because
o f g r a z in g was m easured.
o n ly
one
24
RESULTS AND DISCUSSION
The le a s t- s q u a r e s a n a ly s e s o f v a r ia n c e f o r cow body w e ig h t,
p r o d u c tio n and c a l f w e ig h t f o r
p re s e n te d i n
m ilk
th e a n im a ls used d u r in g th e s tu d y a re
t a b l e 2 . The b re e d t y p e m eans a n d s t a n d a r d e r r o r s f o r
th e s e t r a i t s
( p e r io d s
I
and 4) a re p re s e n te d i n
A t th e b e g in n in g o f th e s t u d y ( p e r io d
t a b le
I),
3.
t h e S im m e n ta l c r o s s
c o w s ( I SI H a nd 3S1H) w e re h e a v ie r (P < .0 1 ) t h a n t h e H e r e f o r d co w s b u t
n o t h e a v ie r th a n th e Angus x H e re fo rd cows.
The Angus x H e re fo rd
cows
w e re n o t s i g n i f i c a n t l y d i f f e r e n t fro m e i t h e r th e H e re fo r d o r S im m e n ta l
c ro s s cows.
of
th e
A l l b re e d ty p e s m a in ta in e d
tr ia l.
S im ilia r
r e s u lts
A g r i c u l t u r a l R e s e a rc h C e n te r ,
p r o g r e s s iv e ly
in c re a s e d
t h e i r w e ig h t f o r
w e re
o b s e rv e d ,
at
by C a s e b o lt (1 9 8 4 ).
d u r in g th e
p o s t peak m i l k
o f l a c t a t i o n a n d no d i f f e r e n c e s w e re fo u n d i n
th e d u r a t io n
th e
N o rth e rn
Cow b o d y w e ig h t
p r o d u c tio n
th e c y c l i c
p o r t io n
changes i n
body w e ig h t betw een th e s e same f o u r b re e d ty p e s .
The S im m e n ta l c ro s s cows p ro d u ce d s i g n i f i c a n t l y m ore (P<.05) m il k
th a n e i t h e r
( ta b le
3) ,
d iffe r e n c e
t h e HH o r AH c o w s a t t h e s t a r t o f t h e s t u d y ( p e r io d
but
by
in
m ilk
th e
end
of
th e
p r o d u c t io n
I
to
4.
C a s e b o lt
( p e r io d
b e tw e e n t h e f o u r
S im m e n ta l c ro s s cows s i g n i f i c a n t l y
p e r io d s
s tu d y
d e cre a se d i n
(1 9 8 4 )
re p o rte d
4) t h e r e
b re e d ty p e s .
m ilk
d if f e r e n c e s i n
d is a g r e e m e n t ,
in
th e
th e
sh ap e
s im ilia r
sh a p e o f t h e l a c t a t i o n
of
th e
la c ta tio n
no
The
p r o d u c tio n fro m
d if f e r e n c e s w i t h r e s p e c t t o th e le v e l o f m i l k p r o d u c tio n ,
b re e d t y p e
was
I)
b re e d
ty p e
b u t fo u n d no
c u r v e s . T h is
c u rv e s ,
c o u ld
be
25
T a b le 2 .
L e a s t-s q u a re s a n a ly s e s o f v a r ia n c e f o r cow body w e ig h t (BW),
m il k p r o d u c tio n (MP) and c a l f w e ig h t (CW)
Mean sq u a re s
S ource
B reed ty p e
df
(B)
BW
(k g 2 )
3
8 0 6 8 **
G roup ( G)
I
1547.5**
P e rio d (P )
I
S ir e b re e d o f c a l f
I
Sex o f c a l f
I
B xG
3
3760+
B xP
3
95
2 7 0 4 5 **
3
MP
(k g 2/ d 2 )
CW
(k g 2 )
5 9 .0 * *
1535**
21 .1
1 46 0 **
5 7 .0 *
2 0 .7
1.9
3 08 5 6 **
961*
2 6 1 3 **
17.6
45
336
2 2 .0 +
55
I
264
7 .2
9 9 1 1 **
79
1471
1,1.0
199
0 .4 3
0 .3 2
0 .7 8
R e g re s s io n
Age o f c a l f
R e s id u a l
R2 .
+
P C .10
$
PC.05
PC.01
26
T a b le 3.
L e a s t-s q u a re s means and s ta n d a rd e r r o r s f o r cow body w e ig h t
(BW)1 m il k p r o d u c tio n (MP) and c a l f w e ig h t (CW)
T r a it b
'e r io d
I
4
B re e d a
ty p e
N
BW
(k g )
MP
( k g /d )
CW
(k g )
HH
12
552 ± 11°
6 .8 ±
.9 °
155 ± 4 .1 °
AH
12
581 ± 11 cd
7 .6 ± I .0 °
151 + 4 .2 °
IS IH
12
599 ± 12d
11.0 ± I .Od
157 + 4 . 4 cd
3S1H
12
. 600 ± I l d
1 1.7 ± I • 0d
168 ± 4 . I d
HH
12
565 ± 11°
6 .3 ±
.9 °
188 ± 4 . I e
"ah
12
581 ± I l cd
8.1 ± I .0 °
185 ± 4.2®
IS IH
11
594 ± 12d
7 .6 ± I .1 °
196 ± 4 . 4 e f
3S1H
12
601 ± I l d
8 .8 ± I .0 °
206 ± 4 . I f
a HH = H e r e f o r d , AH = 5 0% A n g u s - 5 0% H e r e f o r d , I S I H = 50%
S im m ental-50% H e re fo r d , 3S1H = 75% sim m ental-25% H e re fo rd .
b
M eans i n c o lu m n s w i t h d i f f e r e n t
BW (P C .O I), MP and CW ( P < ,0 5 ) .
s u p e r s c r ip ts
a re
d iffe r e n t
27
a tt r ib u te d
t o e n v ir o n m e n ta l d if f e r e n c e s
b etw e e n t h e tw o s tu d ie s o r i n
th e num ber o f a n im a ls t e s t e d and m e a surem e n ts made.
F o r th e
d u r a tio n
of
th e
tr ia l,
th e
c a lv e s
on 3 S 1 H co w s w e re
h e a v i e r (P C .0 5 ) th a n c a lv e s oh HH a n d AH cow s b u t n o t h e a v ie r th a n
c a lv e s
on
I S IH
cow s.
For
a ll
s i g n i f i c a n t am ount o f w e ig h t fro m
th e
b re e d
ty p e s ,
c a lv e s
g a in e d
a
p e r io d s I t o 4.
The tw o g ro u p s o f 24 cows used d u r in g th e s tu d y w e re d i f f e r e n t i n
b o d y w e ig h t a nd c a l f w e ig h t b u t n o t i n
m ilk
p r o d u c t io n .
The g r o u p
m eans ( g r o u p I , g r o u p 2) w e re 570 and 598 k g f o r b o d y w e ig h t ; 1.80 and
172 k g f o r c a l f w e i g h t ; a n d 9.0 a n d 8 .0 k g / d f o r m i l k p r o d u c t io n . The
d if f e r e n c e
in
body w e ig h t b e tw e e n t h e tw o g ro u p s o f cows was m a in ly
due t o t h e 3S1H co w s i n
3S1H c o w s i n
g ro u p
I.
g r o u p 2 b e in g 86 k g h e a v i e r (P C .0 1 ) th a n t h e
F o r a l l b re e d ty p e s ,
h e a v ie r (PC.01) th a n th e c a lv e s i n
c a lv e s i n
g ro u p I w e re
g r o u p 2.
D a ily G ra z in g H ours
The le a s t- s q u a r e s a n a ly s is o f v a r ia n c e f o r d a i l y g r a z in g h o u rs i s
p re s e n te d i n
t a b le 4. S i g n i f i c a n t s o u rc e s o f v a r i a t i o n in c lu d e d g ro u p ,
c o w (b re e d x g ro u p ),
p e r io d ( g r o u p ) ,
d a y (g ro u p x p e r io d ) and bre ed ty p e
x p e r io d ( g r o u p ) .
The o v e r a l l
d e v ia t io n
d a ily
o f 1.08 h r / d
su m m e r r a n g e la n d ,
s im ila r
e s tim a te s
g r a z in g
mean w a s 9.4 h r / d
(633 o b s e r v a tio n s ) .
D w yer
(1 9 6 1 )
For la c ta tin g
a nd N e ls o n
o f 9.7 and 10.0 h r / d ,
w ith
and F u r r
r e s p e c t iv e ly ,
a s ta n d a rd
cows g r a z in g
( 196.6) fo u n d
w h ile
G onzalez
(1 9 6 4 ) fo u n d a s l i g h t l y h ig h e r e s tim a te o f 10.6 h r / d .
No s i g n i f i c a n t d i f f e r e n c e s , i n d a i l y g r a z in g h o u r s , w e re f o u n d
b e tw e e n t h e f o u r b re e d t y p e s u se d i n
th is
s t u d y . The o v e r a l l b r e e d
28
T a b le 4 .
L e a s t-s q u a re s a n a ly s is o f v a r ia n c e f o r d a i ly g r a z in g h o u rs
Mean sq u a re s
S o u rc e
df
D a ily
g r a z in g
h o u rs
B reed ty p e
3
4 .8
G roup
I
1 0 3 .1 * *
*
*
P e r io d (g ro u p )
D a y (g ro u p x p e r io d )
B re e d x p e r io d ( g r o u p )
R e s id u a l
R2
40
2
9 2 .4 * *
28
2 .4 * *
6
2 .8 *
549
I .2
0 .5 4
P <.05
98
CO
t-
Cow(breed x g ro u p )
P<.01
(h r^ /d ^ )
29
t y p e m e a ns and s t a n d a r d e r r o r s
w e re 9 .2 + .0 9 ,
a n d 9 .3 ± .09 h r / d
IS IH
K ro p p e t a l .
HE,
AH,
a nd
3S1H c o w s ,
( 197 3) a ls o f o u n d n o d i f f e r e n c e s i n
b e tw e e n H e r e f o r d ,
h e ife r s
fo r
g r a z in g
9.6 + .0 9 ,
r e s p e c t iv e ly .
d a i l y g r a z in g t i m e
H o ls te in and H e re fo rd x H o ls te in
n a tiv e
s i g n i f i c a n t d if f e r e n c e s
ra n g e
b u t, S tr ic k lin
b etw e e n l a c t a t i n g
et
n o n - la c t a tin g
a l.
(1 9 7 6 )
fo u n d
Angus and C h a ro la is x Angus
c o w s g r a z in g s m a ll a l f a l f a - o r c h a r d - g r a s s p a s t u r e s .
b re e d ty p e d if f e r e n c e s , i n
9 .2 + .10
It
seem s t h a t
th e am ount o f tim e s p e n t f o r a g in g f o r fo o d ,
a r e d e p e n d e n t u p o n t h e t y p e o f f o r a g e b e in g co n s u m e d . On r a n g e la n d ,
a n im a ls w i t h lo w e r e n e rg y demands can g ra z e more s e l e c t i v e l y and th u s
h a ve lo w e r in t a k e
B ecause
r a t e s t h a n a n im a ls w i t h
tw o
g ro u p s
of
cow s
w e re
h i g h e r e n e rg y d em an d s.
used
d u r in g
th e
s tu d y ,
c o m p a r is io n s o f t h e p e r io d m eans can o n l y be made b e tw e e n p e r io d s I
v s . 3 and 2 v s . 4.
G ra z in g h o u rs s i g n i f i c a n t l y
in c re a s e d
(P<.01) fro m
p e r io d s I t o 3 and f r o m 2 t o 4 . The d a i l y g r a z in g h o u r s w e re 8.0 and
9.8 h r / d f o r
p e r io d s I and 3, r e s p e c t iv e ly ,
p e r io d s 2 and 4 ,
and 9.5 and 10.0 h r / d
fo r
r e s p e c t iv e ly .
The in c r e a s e s i n g r a z in g t i m e b e tw e e n p e r io d s i s l i k e l y due t o
d e c re a s e s i n fo r a g e q u a l i t y and q u a n t it y
W h it t a k e r ,
a l.
1970;
(1 9 8 5 ) fo u n d
in c r e a s e fro m
A rn o ld and D u d z in s k i,
g r a z in g
t im e s
( A r n o ld ,
1978). I n U ta h ,
on c r e s t e d
6.3 t o 10.9 h r / d when fo r a g e a v a i l a b i l i t y
s tu d y ,
th e s t o c k in g r a t e
A lld e n a n d
S c a rn e c c h ia e t
w h e a tg ra s s
919 t o 144 k g DM/ha. A lth o u g h fo r a g e a v a i l a b i l i t y
th is
I9 6 0 ;
p a s tu re s t o
d e crea se d fro m
was n o t m easured i n
o f 1.0 ha/AUM s h o u ld have s i g n i f i c a n t l y
d e p le te d th e f o r a g e r e s o u r c e .
The i n t e r a c t i o n
b e tw e e n b re e d and p e r io d ( g r o u p ) i s
p re s e n te d i n
30
t a b le 5.
A l l b re e d ty p e s s i g n i f i c a n t l y
p e r io d s I t o 3 and a l l
in c re a s e d i n
g r a z in g t im e fro m
b re e d ty p e s e x c e p t AH in c re a s e d fro m
p e r io d s 2
t o 4 . AH c o w s g r a z e d lo n g e r (P C .0 5 ) t h a n HH and 3S1H co w s i n p e r io d 2
a n d lo n g e r t h a n HH, IS IH a nd 3STH c o w s i n
p e r io d 3. I n p e r io d 4 , t h e
3S1H c o w s g r a z e d l o n g e r th a n a l l t h e o t h e r b re e d t y p e s . I t a p p e a r s
t h a t th e AH cows re s p o n d e d d i f f e r e n t l y
C h anges i n
fo r a g e
c o n d itio n s .
th a n th e o th e r b re e d ty p e s to
B e ca u se
of
g r a z in g on ra n g e la n d , fo r a g e a v a i l a b i l i t y
a re a t o
a n o th e r.
g r a z in g
p e r io d
d is tr ib u tio n
of
D if f e r e n c e s
c o u ld
be
g r a z in g .
is
h ig h ly v a r ia b l e
fro m
of
one
b etw e e n b re e d ty p e s d u r in g a p a r t i c u l a r
a ttr ib u te d
In
th is
d ep e nd e nt upon th e fo r a g e q u a l i t y
g r a z in g a n d t h e
unequal d is tr ib u tio n
to
case,
th e
d iffe r e n c e s
g r a z in g
and q u a n t it y
in
t im e
is
in
th e
p r o b a b ly
th e a re a s
th e y a re
d e g re e o f s e l e c t i v i t y b e in g e xp re sse d .
The r e s id u a l c o r r e la t io n s , b etw e e n th e g r a z in g b e h a v io r v a r ia b le s
and th e
cow and c a l f t r a i t s
m easured i n
th is
s tu d y ,
a re p re s e n te d i n
t a b l e I 3 ( a p p e n d ix ) . To d e t e r m in e t h e e f f e c t o f th e cow b o d y w e ig h t ,
cow m il k p r o d u c tio n ,
g r a z in g h o u rs ,
h ig h ly
c a l f w e ig h t,
c a l f age and cow c o n d it io n on d a i ly
s e v e r a l a n a ly s e s w e re made t o a v o id th e use o f any tw o
c o r r e la t e d in d e p e n d e n t v a r ia b le s .
c o r r e la te d
w ith
c o r r e l a t e d w it h
Of th e f i v e
cow
c o n d it io n
( .8 9 )
Cow body w e ig h t
and
c a lf
w e ig h t
was h ig h ly
was
h ig h ly
c a l f age (.7 1 ).
cow and c a l f t r a i t s
used as c o v a r ia te s i n th e d a i ly
g r a z in g m o d e l, o n ly cow m il k p r o d u c tio n and c a l f age had a s i g n i f i c a n t
in f lu e n c e
on d a i l y g r a z in g h o u r s ( t a b l e 6 ) . When age o f c a l f and cow
body w e ig h t w e re in c lu d e d i n
th e m o d e l,
an in c re a s e o f one k g /d above
t h e m ean l e v e l o f m i l k p r o d u c t io n (8 .5 k g / d ) c a u s e d a ,0 5 ± .03 h r / d
31
T a b le 5 .
L e a s t - s q u a r e m eans a nd s t a n d a r d e r r o r s f o r d a i l y g r a z in g
■ h o u rs ( h r / d ) o f t h e i n t e r a c t i o n b e t w e e n b r e e d a n d
p e r i od ( g r o u p ) 13
G roup
2
B re e d a
Type
I
P e rio d
I
P e rio d
2
3
8.1 + .2 1 °
(3 1 )
IS IH
CO
3S1H
7 .9 ± .1 9 °
(3 9 )
O
AH
,O U
rr
CVJ
8 .3 ± .1 7 °
(4 8 )
+1 CO
O
HH
a R e fe r t o f o o t n o t e i n
9-9 ± .1 5 e f
(4 8 )
10.4 + .16 6
(4 6 )
9.1 ± .1 7 °
(4 1 )
10.0
± .2 0 de
(3 4 )
4
9 -7 ± .2 1 f
(3 1 )
1 0.0 + .1 7 '
(4 3 )
9 .1 ± .2 4 d
(3 0 )
9 .5 + .20°®
(3 6 )
1 0 .0 + .1 7 f
(4 3 )
9 .7 + .1 7 d f
(4 4 )
9 .4 + .1 6 °
(4 7 )
10.4 + . I 8 h
(4 0 )
t a b le 3 .
^ Means i n ro w s and colum ns ( w i t h in g ro u p ) w it h d i f f e r e n t s u p e r s c r ip t s
a re d i f f e r e n t (P < . 0 5 ) . Number o f o b s e r v a tio n s i n p a r e n th e s is .
32
T a b le 6 .
E f f e c t s o f c o v a r ia t e s on d a i l y g r a z in g h o u rs
C o v a ria te
P a r t i a l r e g r e s s io n c o e f f i c i e n t
Age o f c a l f
- .02
M ilk p r o d u c tio n
.0 5
h r/d /k g /d *
Cow body w e ig h t
- .003 h r / d / k g
Cow c o n d it io n
-.1 2
(w t/h t)
C a lf w e ig h t
*
h r /d /k g /c m
- .003 h r / d / k g
P <.05
ss
PC.01
in c re a s e
to
h r/d /d * *
in
d a ily
g r a z in g h o u rs .
Thus,
m ore t im e g r a z in g i s
s u p p o rt th e e n e rg y c o s ts a s s o c ia te d w i t h
r e q u ir e d
in c re a s e d l e v e ls
o f m ilk
p r o d u c t io n . U s in g .6 7 k c a l / h r a s t h e e n e rg y c o s t o f g r a z in g (H o lm e s ,
1978), th e in c r e a s e i n
be
.0 4
k c a l/k g
of
th e a n im a l's m a in te n a n c e r e q u ir e m e n t w o u ld o n ly
m ilk
p ro d u c e d .
T h e re fo re ,
th e
p r o d u c t io n h a s on th e e n e rg y c o s t o f g r a z in g i s
e v e ry
one day in c r e a s e
above th e a v e ra g e
g r a z in g h o u rs d e cre a se d by .02 + .01 h r / d
in flu e n c e
m in im a l .
m ilk
A ls o ,
fo r
c a l f age (1 0 5 d ) , d a i l y
(PC.01).
The n e g a tiv e
e ffe c t
o f c a l f age c o u ld p o s s ib ly be due t o th e cows s ta g e o f l a c t a t i o n . Cows
w it h o ld e r c a lv e s w e re i n
a l a t e r s ta g e o f l a c t a t i o n and pro du ce d le s s
m il k th a n cows w it h y o u n g e r c a lv e s .
C o n s id e rin g a l l
th e in d e p e n d e n t v a r ia b le s
had th e m o s t im p o r t a n t in f lu e n c e
on d a i l y
to g e t h e r ,
age o f c a l f
g r a z in g h o u rs .
The s ta n d a rd
p a r t i a l r e g r e s s io n c o e f f i c i e n t s f o r age o f c a l f ,
m il k p r o d u c tio n ,
cow
b o d y w e i g h t , cow c o n d i t i o n a nd c a l f w e i g h t w e re - . 0 7 , .0 6 , - . 0 4 , -.0 1
33
and
-.0 1 ,
r e s p e c tiv e ly .
S tr ic k lin
et
a l.
( 1976)
fo u n d
s im ila r
r e l a t i o n s h i p s b e tw e e n cow w e ig h t a nd c a l f w e ig h t a n d d a i l y g r a z in g
h o u rs h o w e v e r; c a l f age was n o t a s i g n i f i c a n t s o u rc e o f v a r i a t i o n and
th e
p a r tia l
c o r r e la tio n
was p o s i t i v e
(.2 3 ).
S t r i c k l i n ’ s s tu d y
w as
c o n d u c te d on s m a ll p a s t u r e s d u r in g May and J u n e w i t h y o u n g c a lv e s .
U nder th e s e c o n d it io n s ,
as o b s e rv e d i n
th is
th e s ta g e o f l a c t a t i o n may n o t be as im p o r t a n t
s tu d y .
Time o f Day G ra z in g
The
le a s t- s q u a r e s
g r a z in g t o o k p la c e a r e
g r a z in g h o u rs ,
a n a ly s e s
of
p re s e n te d i n
v a r ia n c e
ta b le s
fo r
th e
t im e
of
7 a n d 8. As w i t h
day
d a ily
cow and day w e re im p o r t a n t s o u rc e s o f v a r i a t i o n i n t im e
o f day g r a z in g . B reed ty p e was s i g n i f i c a n t d u r in g th e 900-1200 h r t im e
p e r io d a nd p e r io d ( g r o u p ) was s i g n i f i c a n t i n a lm o s t a l l o f t h e 3 - h r
tim e
p e r io d s s tu d ie d .
was im p o r t a n t
(P<.05) d u r in g
The o v e r a ll tim e
The m a j o r i t y
The i n t e r a c t i o n
b etw e e n b re e d and p e rio d (g ro u p )
300 -6 0 0 and 1800-2100 h r.
o f day g r a z in g means a re p re s e n te d i n
o f g r a z in g to o k p la c e
fig u r e
2.
b e tw e e n 600-900 and 1800-2400 h r .
S e c o n d a ry p e r io d s o f g r a z in g r a n g in g f r o m
.5 (2 4 0 0 -3 0 0 h r ) t o
'.9
hr
(1 5 0 0 -1 800 h r ) w e r e r e c o r d e d .
A s i m i l a r p a t t e r n o f g r a z in g a c t i v i t y
F u r r (1966) u s in g l a c t a t i n g
on
su m m e r
r a n g e la n d
in
was o b s e rv e d by N e lso n and
cows and K ro pp e t a l (1973) u s in g h e i f e r s
O k la h o m a .
A ls o
u s in g
la c t a t in g
cow s i n
O klahom a, D wyer (1961) fo u n d s i m i l a r r e s u l t s w it h r e s p e c t t o th e m a jo r
g r a z in g p e r io d s ,
b u t cow s i n
m o r n in g a n d l e s s
d u r in g
s tu d y .
th e
t h e i r s t u d y g r a z e d m o re i n
a fte rn o o n
t h a n th e
th e e a r ly
co w s u s e d i n
th is
34
T a b le 7 •
L e a s t-s q u a re s a n a ly s e s o f v a r ia n c e f o r tim e o f day
(2 4 00 -1 2 00 h r ) .
g r a z in g
Mean sq u a re s
Time o f day g r a z in g ( h r 2 )
Time o f Day (x 100 h r )
S ource
df
3
G roup
I
Cow(breed x g ro u p )
P e r io d (g ro u p )
D a y(g ro u p x p e r io d )
B re e d x p e r io d ( g r o u p )
R e s id u a l
R2
+
P C .10
*
PC.05
PC.01
6
339*
3 -6
6 -9
9 -12
75
93
153+
81
7 1 4 **
T W **
40
5 3 **
9 4 **
9 0 **
6 5 **
2
2 4 0 **
2 9 9 **
7 4 8 **
7 5 7 **
54*
7 7 **
6 2 **
Co
CO
B re ed ty p e
2 4-3
6
23
68*
51
12
549
31
25
30
34
0 .2 2
0 .3 5
0 .3 5
0 .3 0
28
35
T a b le 8 .
L e a s t - s q u a r e a n a ly s e s o f v a r ia n c e f o r t im e o f day g r a z in g
(1 2 00 -2 4 00 h r ) .
Mean s q u a re s
Time o f da;7 g r a z in g ( h r 2 )
12-15
1 5-18
18-21
31
119
20
302
710 *
116s *
1 5 5 **
1 2 3 **
18
9 2 4 **
136+
B reed ty p e
3
100
G roup
I
83
R e s id u a l
R2
+
P<.10
*
P<.05
88
P<.01
175*
28
78*
6
92+
82+
47
45
35
49
0 .2 2
0 .2 9
0 .3 9
0 .2 9
549
O
2
ro
B re ed x p e r io d ( g r o u p )
21-24
7 3 **
1 7 8 **
Nt
Ne
CO
VJD
DayCgroup x p e r io d )
CO
P e r io d (g ro u p )
40
O
CowCbreed x g ro u p )
CO
df
Ul
S ource
ro
O
Time o f day (x 100)
96+
36
2 . 0-
Time Of Day (x
F ig u r e 2 .
100 h r )
O v e r a ll tim e o f day g r a z in g means.
B e tw e e n 9 0 0 -1 2 0 0 h r , t h e AH c o w s g r a z e d lo n g e r (P < .0 5 ) t h a n a l l
th e o t h e r b re e d t y p e s . B re e d t y p e
m e a ns and s t a n d a r d e r r o r s f o r BH,
AH,
I SI H and 3S1H co w s w e re .8 + .0 5 ,
h r,
r e s p e c tiv e ly .
p e r io d (g ro u p )
B ecause
in t e r a c t io n
th e re
d u r in g
.9 ± .0 5 ,
w as no
th is
t im e
.7 ± .05 and .8 + .05
s ig n if ic a n t
p e r io d ,
th is
b re e d
ty p e
x
r e la t io n s h ip
h e l d t r u e d u r in g a l l f o u r o f th e g r a z in g p e r io d s . The l o n g e r g r a z in g
37
tim e s re c o rd e d by t h e ' AH cows d u r in g 900-1200 h r w o u ld a c c o u n t f o r th e
lo n g e r g r a z in g tim e s re c o rd e d f o r th e AH cows d u r in g g r a z in g p e r io d s 2
and 3.
F rom p e r io d s I t o 3 ( g r o u p 2 ) , s i g n i f i c a n t in c r e a s e s i n g r a z in g
t im e w e re f o u n d f o r f o u r o u t o f t h e e i g h t 3 - h r t im e
9 ).
G r a z in g
tim e
r e m a in e d f a i r l y
p e r io d s
( ta b le
c o n s t a n t b e tw e e n 3 0 0 -6 0 0 h r and
b etw e e n 1500-2400 h r and s i g n i f i c a n t l y in c re a s e d d u r in g a l l o th e r tim e
p e r io d s .
T a b le 9 .
L e a s t - s q u a r e s m eans f o r t i m e o f day g r a z in g
(h r)a
Group
2
I
P e rio d
Time
0 .3 b
Mean
Temp.
4
0 .6 b
0 .9 b
——
0 .8 b
19
0600-0900
1 .8 b
2 .3 °
2 .3 b
2 .4 b
20
0900-1200
0 .5 b
0 .8 °
0 .8 b
1 .1 °
24
1200-1500
0 .6 b
0 .9 °
0 .8 b
0 .9 b
26
1500-1800
I .Ob
0 .9 b
0 .7 b
1800-2100
1 .7 b
1 .6 b
2 .1 °
26
2100-2400
1 .3 b
1 .5 b
1 .7 b
1 .6 b
25
a
M eans i n r o w s , w i t h i n
d i f f e r e n t (P C .0 1 ).
g ro u p ,
w ith
d if fe r e n t
cr
0300-0600
O
O'*
O
&
0 .6 b
CO
O
0 .6 °
O
.
P e rio d
2
3
CO
cr
2400-0300
I
28
s u p e r s c r ip ts
a re
38
F rom p e r io d s 2 t o 4 ( g r o u p I ) , s i g n i f i c a n t in c r e a s e s i n g r a z in g
tim e o c c u re d f o r o n ly tw o o f th e e ig h t 3 - h r tim e p e r io d s . G ra z in g tim e
in c r e a s e d
(P C .0 1 ) b e tw e e n 9 0 0 -1 2 0 0 a nd 18 0 0 -2 1 0 0 h r a nd d e c r e a s e d
(P C .0 1 ) b e tw e e n 3 0 0 -6 0 0 h r .
d u r in g
th e
o th e r
t im e
No s i g n i f i c a n t
d i f f e r e n c e s w e re f o u n d
p e rio d s .
The c h o ic e o f t im e p e r io d t o in c r e a s e g r a z in g t im e and th e le n g t h
of
t im e
q u a n tity
fo u n d
spent
g r a z in g
is
in f lu e n c e d
m ost
by
a nd w e a th e r ( A r n o ld a n d D u d zi n s k i ,
t h a t v a r y in g
th e
s to c k in g
ra te
fo ra g e
1978) .
had l i t t l e
q u a lity
and
A r n o ld (1 9 6 2 )
a ffe c t
upon
th e
d i u r n a l p a t t e r n o f g r a z in g . The m a jo r g r a z in g p e r io d s r e m a in e d t h e
same,
b u t w it h a s h o rta g e o f fe e d a n im a ls r e s t le s s o f t e n and so have
fe w e r and lo n g e r p e r io d s o f g r a z in g .
d a y lig h t h o u rs ,
le n g t h
o f s ta y
te m p e ra tu re
a t w a te r .
D wyer (1961) o b s e rv e d t h a t d u r in g
d ic ta te d
th e
t im e
o f a r r i v a l a n d th e
D u rin g th e p re s e n t s tu d y ,
th e m a jo r g r a z in g
p e r io d s a ls o r e m a in e d th e same t h r o u g h o u t t h e g r a z in g p e r io d a n d no
in c r e a s e s i n
g r a z in g t i m e w e re f o u n d b e tw e e n 1500 and I 800 h r ,
th e
w a rm e s t tim e p e r io d o f th e day ( t a b le 9).
The i n t e r a c t i o n
a nd I 8 0 0 -2 1 0 0 h r i s
b e tw e e n b re e d and p e r io d (g ro u p ) d u r in g 300-600 h r
p re s e n te d i n
ta b le
10. The i n t e r a c t i o n s
d u r in g
t h e s e tw o t im e p e r io d s w a s m a in ly due t o f l u c t u a t i o n s i n g r a z in g by
th e I SIH cows. From p e r io d s I t o 3,
th e I SIH cows in c re a s e d
g r a z in g t i m e b e tw e e n 3 0 0 -6 0 0 h r w h i l e
(PC.05) i n
t h e HH and AH co w s s l i g h t l y
d e c r e a s e d . B e tw e e n I 8 0 0 -2 1 0 0 h r , t h e I SIH cow s d e c r e a s e d (P C .0 1) i n
g r a z in g t im e w h ile
th e o th e r b re e d ty p e s in c re a s e d .
4 , t h e IS IH a nd 3S1H co w s d e c r e a s e d (P C .0 5) i n
3 0 0 -6 0 0 h r w h ile th e HH and AH cows s l i g h t l y
From p e r io d s 2 t o
g r a z in g t im e b e tw e e n
d e cre a se d .
B etw een 1 800-
39
T a b le
10.
L e a s t-s q u a re means f o r t im e o f day g r a z in g (0 3 00 -0 6 00 and
1800-2100 h r) f o r th e i n t e r a c t i o n betw een b re e d ty p e and
p e r io d ( g r o u p ) 13
Group
2
Time
P e rio d
0300-0600
1800-2100
B reed
Typea
I
P e rio d
I
P e rio d
3
2
4
HH
0 . 8°
0 . 6°
0 .7 °
0 . 6° °
AH
0 . 8°
0 .7 °
0 .7 °
0 .5 ° °
I.Id
0 .9 cd
0 .7 °
IS IH .
0 .7 °
3 SI H
0 . 8°
0 . 8°
I .Od
0 .5 °
HH
1 . 6°
2.Id
1. 8°
2 .3 d
AH
1 . 6°
2 . Od
1 .5 °
I .9 °
IS IH
1 . 8°
1. 2°
1 . 8°
2 . Ode
1 . 6°
1 .9 d
I .5 °
2 .3 d
3S1H
a R e fe r t o f o o t n o t e i n
-
t a b le 3 .
k M eans i n . r o w s a nd c o lu m n s ( w i t h i n g r o u p and t i m e p e r io d ) w i t h
d i f f e r e n t s u p e r s c r ip t s a re d i f f e r e n t ; 0 3 0 0 - 0 6 0 0 h r (P C .0 5 ) , I 8 0 0 2100 h r (P C .0 1 ) .
40
2100 h r ,
ty p e s
th e
I SI H cows o n ly s l i g h t l y
s ig n ific a n tly
d if f e r e n c e s
H o ls te in
H o ls te in
in
in c r e a s e d .
th e t im e
in c re a s e d w h ile
K ro p p
et
(1 9 7 3 )
a ls o
g ra z e d
lo n g e r
in
th e
D u r in g J u l y a n d A u g u s t,
e v e n in g
th a n
H e re fo r d and
H e re fo r d x H o ls t e in h e if e r s and H e re fo r d x H o ls t e in h e if e r s
lo n g e r th a n H e re fo r d and H o ls t e in h e i f e r s i n
d if f e r e n c e s
fo u n d
o f day t h a t g r a z in g to o k p la c e f o r H e re fo rd ,
and H e re fo rd x H o ls t e in h e i f e r s .
h e ife r s
al
th e o th e r b re e d
e x is t e d was n o t known.
th e a fte r n o o n .
D if f e r e n c e s
g ra z e d
Why th e s e
betw e e n b re e d s d u r in g
p a r t i c u l a r t im e p e r io d s c o u ld be a t t r i b u t e d t o d if f e r e n c e s i n re s p o n s e
to
changes i n
B ecause
in f lu e n c e
body
w e a th e r
m ilk
on d a i l y
w e ig h t,
p a t t e r n s and fo r a g e a v a i l a b i l i t y .
p r o d u c tio n
a nd
g r a z in g h o u rs ,
in
each
of
age
of
c a lf
had
an
th e y w e re in c lu d e d ,
th e
t im e
of
day
g r a z in g
im p o r t a n t
a lo n g w it h
cow
m o d e ls .
T he
r e s id u a l c o r r e la t io n s b etw e e n tim e o f day g r a z in g and th e cow and c a l f
v a r ia b l e s a re p re s e n te d i n t a b le
The
e ffe c t
of
m ilk
13 ( a p p e n d ix ) .
p r o d u c t io n
was
m a in ly
e x p re s s e d
(P < \0 5 )
b e tw e e n 2 4 0 0 - 3 0 0 , 6 0 0 -9 0 0 and 1 5 0 0 -1 8 0 0 h r . The p a r t i a l r e g r e s s io n
c o e f f i c i e n t s f o r m i l k p r o d u c t io n w e r e .03 + .01 , - . 0 3 ± .01 a nd .03 +
0 .0 1 h r / d / k g / d
f o r 2 4 0 0 - 3 0 0 , 6 0 0 -9 0 0 and 1500-1800 h r , r e s p e c t iv e ly .
The l e v e l o f m i l k
p r o d u c t io n h a d i t ' s
b e tw e e n 2 4 0 0 -3 00 h r .
s tr o n g e s t in f lu e n c e
T h is w o u ld a g re e w it h
t h e te n d e n c y f o r h i g h e r m i l k i n g
cow s to
(P < .0 1)
S tob b s (1975) who r e p o r te d
g r a z e m o re a t
n ig h t.
The
e f f e c t o f c a l f age w a s m a in ly e x p r e s s e d (P < .0 5 ) b e tw e e n 3 0 0 -6 0 0 and
I 8 0 0 -2 1 0 0 h r . The p a r t i a l r e g r e s s io n
and
-.0 1
+
r e s p e c t iv e ly .
.0 0 5
h r/d
of
c a lf
age
c o e ffic ie n ts
fo r
3 0 0 -6 0 0
and
w e re .01 + .004
1 8 0 0 -2 1 0 0
h r,
41
S tr ic k lin
e t a l.
(1976) fo u n d cow body w e ig h t as a s i g n i f i c a n t
s o u rc e o f v a r i a t i o n i n e x p la in in g t o t a l n ig h t h o u rs s p e n t g ra z in g .
p a r tia l
c o r r e la t io n
(-.2 0 )
was n e g a tiv e ,
g r a z e d m o re a t n i g h t . I n t h i s s t u d y ,
(P<.01) s o u rc e
o f v a r ia tio n in
in d i c a t i n g
The
t h a t s m a lle r cows
cow b o d y w e ig h t w as i m p o r t a n t
g r a z in g t im e betw e e n 1800-2100 h r ,
th e p a r t i a l r e g r e s s io n c o e f f i c i e n t (.005 h r / k g ) was so lo w
th a t i t
but
was
b i o l o g i c a l l y u n im p o rta n t.
D is ta n c e T r av e le d
The le a s t- s q u a r e s
p re s e n te d i n
of
v a r ia n c e
t a b l e . 1 1 . B re e d t y p e ,
b re e d ty p e x s i r e
in
a n a ly s is
fo r
d is ta n c e
p e r io d ( g r o u p ) ,
t r a v e le d i s
sex o f
c a lf and
b re e d o f c a l f w e re s i g n i f i c a n t s o u rc e s o f v a r i a t i o n
d is ta n c e t r a v e l e d .
The o v e r a ll mean and s ta n d a rd d e v ia t io n f o r d is ta n c e t r a v e le d was
4 .7 ± 0 .9 k m /d (8 2 o b s e r v a t io n s ) .
The b re e d t y p e m eans a n d s t a n d a r d
e r r o r s w e r e 5 .0 ± . 2 , 4 .8 ± .2 , 4.1 + .2 and 4 .8 + .2 k m /d f o r BH, AH,
IS IH and 3STH cows,
r e s p e c t iv e ly .
I SIH cows t r a v e le d le s s th a n (P<.05)
HH, AH and 3S1H c o w s a n d t h i s r e l a t i o n s h i p h e ld t r u e d u r in g t h r e e o f
th e f o u r
fo r
g r a z in g
le n g t h
p e r io d s . Because th e
o f s t r id e
d if f e r e n c e s
p e d o m e te rs w e re n o t
c a lib r a t e d
b e tw e e n th e f o u r b re e d ty p e s ,
it
is
p o s s i b l e t h a t t h e b re e d t y p e d i f f e r e n c e s , i n d is t a n c e t r a v e l e d , a r e
due t o
d iffe r e n c e s
in
le n g t h
of
s tr id e .
B re e d t y p e
m eans f o r
cow
h e i g h t w e re 1 2 9 , 1 2 9 , 134 a nd 135 cm f o r HH, AH, IS IH a nd 3S1H c o w s ,
r e s p e c t i v e l y . The S im m e n ta l c r o s s c o w s ( IS IH and 3S1H) w e re t a l l e r
(P<.05) th a n th e HH and AH cows and c o u ld have a lo n g e r s t r i d e
a n d AH c o w s h o w e v e r ,
th e d is ta n c e
t h e ra w
c o r r e la tio n
t r a v e le d was o n ly -.0 4 .
th a n HH
b e tw e e n cow h e i g h t a n d
42
T a b le 11.
L e a s t-s q u a re s a n a ly s is o f v a r ia n c e f o r d is ta n c e t r a v e le d
Mean sq u a re s
S ource
df
B re ed ty p e
(B)
D is ta n c e t r a v e le d
3
2 6 .6 *
I
1.1
2
2 8 .0 *
Sex o f c a l f (S x)
I
8 9 .7 * *
S ir e b re e d o f c a l f (S)
I
11.1
B x P/G
9
1 2.3
B xS
3
1 7 .0+
I
0 .0
60
7 .5
G roup (G)
P e rio d (G ro u p )
(P/G )
(km2/ d 2 )
R e g re s s io n
Age o f c a l f
R e s id u a l
R2
+
8
0 .3 3
P<.10
P< .05
SS
P<.01
t
The d is ta n c e t r a v e le d v a lu e s r e p o r te d h e re a re s i m i l a r t o th o s e
re p o r te d
b y G o n z a le z
r e s p e c t iv e ly ,
f o r cows g ra z in g , on a s i m i l a r s iz e p a s tu re b u t le s s th a n
th o s e r e p o r te d
S a n ta G e r t r u d is
by H e rb e l and N e lso n ( 1 966) f o r H e re fo rd (6.9 km /d ) and
(14.6 k m /d ) cows g r a z in g on a 1464 ha. p a s tu re .
D is t a n c e t r a v e l e d
p e r io d
I to
( 1 9 6 4 ) a nd D w y e r (1 9 6 1 ) o f 4 .0 a n d 5 .0 k m /d ,
in c r e a s e d
(P C .0 5 ) f r o m
p e r io d 3 and re m a in e d f a i r l y
4 .3 t o
c o n s ta n t fro m
5 .0 k m /d f r o m
p e r io d s 2 t o 4
43
(4 .6 a nd 4 .9 k m /d , r e s p e c t i v e l y ) . From p e r io d
t r a v e le d f o llo w e d
th e same g e n e ra l tr e n d
h r / d w e re s p e n t g r a z in g f o r
I t h r o u g h 4 , d is t a n c e
as d a i ly
g r a z in g h o u rs .
Two
e v e r y k m /d o f t r a v e l i n a l l f o u r o f t h e
g r a z in g p e r io d s .
Cows w i t h
s t e e r c a lv e s t r a v e l e d f a r t h e r (P < .0 1) t h a n co w s w i t h
h e i f e r c a lv e s a n d t h i s r e l a t i o n s h i p
a c ro s s a l l
p e r io d s .
h e i f e r and s t e e r
h e ld
Why
d is t a n c e
on d is ta n c e
c a lf
b re e d ty p e s
c a lv e s , r e s p e c t iv e ly .
th e d is ta n c e t r a v e le d m o d e l,
e ffe c t
fo r a ll
S ex m eans w e re 4 .3 ' and 5.0 k m /d f o r co w s w i t h
When a l l o f t h e cow and c a l f t r a i t s
any
tru e
se x was
tr a v e le d
is
o n ly cow c o n d it io n
t r a v e le d
s i g n i f i c a n t when c a l f age,
in
c le a r ly
e x p la in in g
u n d e rs to o d .
c a l f w e ig h t,
and cow c o n d it io n w e re used i n
came c lo s e
t o h a v in g
(PC.20).
im p o r t a n t
not
w e re u s e d a s c o v a r i a t e s i n
th e
C a lf
cow w e ig h t,
v a r ia tio n
in
s e x r e m a in e d
m il k
p r o d u c tio n
th e m o d e l.
D i s t r i b u t i o n o f G ra z in g
The I e a s t-s q u a r e s a n a ly s is o f v a r ia n c e t a b le f o r d i s t r i b u t i o n
g r a z in g i s
to
p re s e n te d i n
c a lc u la te
t a b le
d is tr ib u tio n
d u r in g g r a z in g p e r io d s I ,
12.
The num ber o f o b s e rv a tio n s /c o w
ra n g e d f r o m
u s e d a s c o n t in u o u s in d e p e n d e n t v a r i a b l e s ,
The mean and s ta n d a rd d e v ia t io n
used
16 t o 22 and w e re r e c o r d e d
2 a n d 4 . Of t h e f i v e
s i g n i f i c a n t in f lu e n c e on d i s t r i b u t i o n
of
cow a nd c a l f t r a i t s
o n ly c a l f w e ig h t h a d a n y
o f g r a z in g .
fo r
d is tr ib u tio n
103 ± 3 6 h a /c o w .
The p r o p o r t io n
47 c o w s u s e d i n
th e a n a ly s is ra n g e d fro m
o f g r a z in g was
o f th e p a s tu re c o ve re d by each o f th e
21 t o 44%. G i l l e n
e s t im a t in g th e home ra n ge b e h a v io r o f l a c t a t i n g
cows i n
( 1 9 8 3 ),
O regon,
fo u n d
44
T a b le
1 2. L e a s t - s q u a r e s
g r a z in g
a n a ly s is
o f v a r ia n c e
fo r
d is tr ib u tio n
of
Mean sq u a re s
S ource
df
D is t r ib u t io n
B re ed ty p e
3
820
Sex o f c a l f
I
92
S ir e b re e d o f c a l f
I
1638
No. o b s e r v a tio n s
I
497
C a lf w e ig h t
I
5 86 7 *
Cow c o n d it io n
I
1136
38
1309
(h a 2 )
R e g re s s io n s
R e s id u a l
R2
0.21
t h a t c o w s h a d a hom e ra n g e o f 343 ha (17 o b s e r v a t io n s ) i n a 3610 ha
p a s tu re .
The l a r g e r a re a o b se rve d by G i l l e n
n u m b e r o f o b s e r v a t io n s ,
c o u ld be due t o a s m a lle r
a la r g e r p a s tu r e s iz e
and d i f f e r e n c e s i n
p a s tu re to p o g ra p h y . I n c r e a s in g th e n u m b e r o f o b s e r v a t io n s
th e
e s tim a te d
a re a
( G ille n ,
1 983) a n d a n im a ls i n
t r a v e l f a r t h e r d is ta n c e s th a n a n im a ls i n
and Kothm ann,
I I f
93
±
o f g r a z in g .
11
la r g e r p a s tu re s
s m a lle r p a s tu re s
(A n d e rs o n
1980).
T h e re w a s no d i f f e r e n c e
d is tr ib u tio n
d e c re a s e s
and
99
b e tw e e n t h e
The d i s t r i b u t i o n
±
I I
h a /c o w
fo r
fo u r
b re e d
means w e re
RH,
AH,
ty p e s in
th e
105+11,
115 +
I SI H and
3S 1H ,
45
r e s p e c t iv e ly .
s iz e
G ille n
(1983) a ls o o b s e rv e d no d if f e r e n c e s i n home ra n ge
b e tw e e n p u r e b r e d
(H e re fo rd ,
A ngus,
Red A n g u s ) a nd
c ro s s b re d
( H e r e f o r d x A n g u s , H e r e f o r d x Red A n g u s ) c o w s .
The p a r t i a l r e g r e s s i o n c o e f f i c i e n t f o r c a l f w e ig h t w a s .5 + .2
h a /k g .
W ith in
e a c h b re e d t y p e ,
cow s w it h
c a lv e s a b o v e a v e ra g e i n
w e ig h t c o v e r e d a g r e a t e r a r e a o f th e p a s t u r e th a n co w s w i t h
b e lo w
c a lv e s
a ve ra g e i n w e ig h t ( a d ju s te d f o r cow c o n d it io n ) .
The r e a s o n w hy c a l f w e ig h t w a s i m p o r t a n t t o
g r a z in g i s
p r o b a b ly due t o
h e a v ie r c a l f i s
g re a te r
v a r ie ty
in
th e a b i l i t y
d is tr ib u tio n
o f th e c a l f to
b e t t e r c o n d itio n to t r a v e l w ith i t ' s
of
g r a z in g
a re a s .
A lt h o u g h
s i g n i f i c a n t am ount o f th e v a r i a t i o n i n
c a lf
age
c a l f w e ig h t,
tr a v e l.
of
The
m o th e r t o a
e x p la in e d
a
c a l f age was n o t
a s im p o r t a n t as c a l f w e ig h t t o d i s t r i b u t i o n o f g ra z in g . The re a s o n why
c a lf
w e ig h t w a s n o t
d is t a n c e
tr a v e le d i s
s ig n if ic a n t
in
e x p la in in g
p r o b a b ly b e c a u s e t h e
th e
c a lf is
v a r ia tio n
in
n o t r e q u ir e d to
t r a v e l th e same d is ta n c e as th e cow. The d is ta n c e a cow t r a v e l s
can be
a c o m b in a t io n o f m o v e m e n t w h i l e g r a z in g , m o ve m e n t b e tw e e n g r a z in g
a r e a s a n d m o v e m e n t b e tw e e n w a t e r a n d g r a z in g a r e a s w h i l e
needs o n ly t o t r a v e l w it h i t s
A lt h o u g h
m o th e r fro m
th e c a l f
one g r a z in g a re a t o a n o th e r.
cow c o n d i t i o n w as n o t s i g n i f i c a n t i n
e x p la in in g
th e
v a r i a t i o n i n b o th t h e d i s t r i b u t i o n a n d d is t a n c e t r a v e l e d m o d e ls , i t
seems t o
be an im p o r t a n t f a c t o r in f lu e n c in g a n im a l m ovem ent.
good c o n d it io n a re a b le
to
t r a v e l lo n g e r d is ta n c e s and see a g r e a te r
p r o p o r t io n o f th e p a s tu re th a n cows i n
To e xa m in e how
Cows i n
d is t r ib u t io n
of
poor
c o n d itio n .
g r a z in g in f lu e n c e d
cow and c a l f
46
p e rfo rm a n c e
d u r in g
th e g r a z in g season,
m i l k p r o d u c t io n , a lo n g w i t h
u s in g d i s t r i b u t i o n
body w e ig h t and
c a l f a v e r a g e d a i l y g a in , w e re a n a ly z e d
o f g r a z in g and age o f c a l f as c o v a r ia t e s .
The o v e r a ll change i n
to
th e change i n
body w e ig h t mean was 2.4 k g (ra n g e = -12.1
17.9 k g ) d u r i n g t h e g r a z in g s e a s o n . 20% o f t h e v a r i a t i o n
b re e d ty p e ) i n
th e g a in o r lo s s i n
( w ith in
cow body w e ig h t c o u ld be e x p la in e d
by t h e a r e a o f t h e p a s t u r e d c o v e r e d d u r in g t h e g r a z in g s e a s o n . F o r
e v e ry h e c ta r e in c r e a s e above th e a ve ra g e d i s t r i b u t i o n
o f g r a z in g
(103
h a ) , c o w s g a in e d .3 ± .07 k g (P < .0 1) i n b o d y w e ig h t ( a d j u s t i n g f o r age
o f c a l f ) . A n im a ls t h a t u t i l i z e d
a g r e a t e r p r o p o r t i o n o f th e p a s t u r e
p ro b a b ly g ra z e d i n a re a s w h e re fo r a g e was o f b e t t e r q u a l i t y th a n th o s e
a n im a ls
th a t
c o n f in e d
.th e m s e lv e s t o a s m a l l e r p r o p o r t i o n
o f th e
p a s tu r e .
D i s t r i b u t i o n o f g r a z in g h a d n o i n f l u e n c e on c a l f a v e ra g e d a i l y
g a in o r th e c h a n g e i n
c a lv e s
had a la r g e r
m i l k p r o d u c t io n .
g r a z in g
A lt h o u g h c o w s w i t h
d is tr ib u tio n
th a n
co w s w i t h
h e a v ie r
s m a lle r
c a lv e s , th e t r a v e l d id n o t seem t o a f f e c t th e g a in o f th e c a l f and th e
b e n if it s
r e c ie v e d
f o r w e ig h t
by in c re a s e d d i s t r i b u t i o n
g a in a nd n o t m i l k
o f g r a z in g w e re u t i l i z e d
p r o d u c t io n .
Spec u la t i o n and Fut u r e D i r e c tio n
. The o v e r a ll o b je c t iv e ,
a re any d if f e r e n c e s i n
d iffe r e n t
o b je c t iv e ,
ty p e s o f
o f th is
s tu d y ,
e n e rg y e x p e n d itu r e
beef c a ttle
was t o
d e te rm in e i f
betw een f o u r
g r a z in g ra n g e la n d .
th e r e
g e n o t y p ic a lly
To a c c o m p lis h
th is
th e g r a z in g b e h a v io r v a r ia b le s chosen t o m easure w e re tim e
s p e n t g r a z in g , d is ta n c e t r a v e le d a n d . d i s t r i b u t i o n o f g ra z in g .
No d if f e r e n c e s w e re fo u n d i n
th e am ount o f am ount o f tim e
spent
47
g r a z in g
b e tw e e n HE,
in fo r m a tio n ,
d if f e r e n c e s
it
is
e x is t
AH,
IS IH
and 3S1H l a c t a t i n g
d i f f i c u l t , to
d e t e r m in e
b e tw e e n th e s e f o u r
if
cow s.
e n e rg y
b re e d ty p e s .
From
th is
e x p e n d it u r e
Because t im e
g r a z in g in c lu d e s tim e s p e n t e a t in g and tim e s p e n t f o r a g in g ,
sp e n t
th e e n e rg y
c o s t o f g r a z in g i n c l u d e s t h e e n e rg y c o s t o f e a t in g p lu s t h e e n e rg y
c o s t s a s s o c i a t e d w i t h b o th h o r i z o n t a l a n d v e r t i c a l m o v e m e n t w h i l e
g r a z in g .
T h a t p r o p o r t io n o f th e d a i l y
e n e rg y c o s ts o f g r a z in g ,
e n e rg y e x p e n d itu re ,
due t o
th e
c o u ld be d i f f e r e n t betw e e n th e s e b re e d ty p e s
d e p e n d in g u p o n how f a r a nd on w h a t s lo p e t h e a n im a l t r a v e l e d w h i l e
g r a z in g .
In th is
a tte m p t
to
s tu d y ,
id e n t if y
m easurem ent o f d i s t r i b u t i o n
b re e d
ty p e
d iffe r e n c e s
H ow ever, an e s t im a t io n o f a re a u t i l i z a t i o n
b re e d ty p e s
may d i f f e r
in
u tiliz a tio n
The l e v e l o f fo r a g e in t a k e
spent
g r a z in g
(k g /h r).
(h r/d )
B ecause in t a k e
a re a
u tiliz a t io n .
does n o t in d ic a t e how th e s e
o f s lo p in g t e r r a i n .
(k g /d ) i s
m u ltip lie d
in
o f g r a z in g was an
e q u a l to
tim e s
d if f e r e n c e s have
th e
ra te
th e am ount o f tim e
of
been r e p o r te d
fo ra g e
in ta k e
betw een
th e s e
sam e b r e e d t y p e s (W a g n e r, 1 9 8 5 ; K r o n b e r g , 1 9 8 3 ), d i f f e r e n c e s i n t h e
r a t e o f fo r a g e in t a k e
o f b ite
ra te
v a r ia b le s
c o u ld p o s s ib ly e x i s t .
( b it e s /h r )
w o u ld
d if f e r e n c e s i n
and b i t e
be a d e c i s i v e
s iz e
I n ta k e r a t e i s
( k g /b ite ) .
s te p
in
th e p ro d u c t
M easurem ent o f th e s e
d e te r m in in g
w h e re
th e
g r a z in g b e h a v io r e x is t betw een th e s e b re e d ty p e s .
D u r in g t h i s s t u d y , IS IH co w s t r a v e l e d .9 k m /d l e s s th a n HH co w s
a n d .7 k m /d l e s s t h a n HH and AH c o w s . I t i s
th e s e d if f e r e n c e s w o u ld t r a n s l a t e i n t o
or
n o t.
B re e d
ty p e
d if fe r e n c e s
in
d i f f i c u l t , t o d e t e r m in e i f
e n e rg y e x p e n d itu re
e n e rg y
e x p e n d it u r e
d if f e r e n c e s
ca n n o t
d e t e c t e d u n le s s some m e a s u re m e n t o f t h e s lo p e o f t h e t e r r a i n ,
be
over
48
w h ic h th e a n im a l t r a v e le d , i s
The d is ta n c e
known.
an a n im a l t r a v e l s
can be a c o m b in a tio n o f movement
w h ile g r a z in g , movement betw een g r a z in g a r e a s a n d m o v e m e n t b e tw e e n
w a te r
a nd
d is t a n c e
g r a z in g
a re a s .
In
th is
some d if f e r e n c e s i n
fre q u e n c y
w a te r,
IS IH
cow s t r a v e le d
le s s
(P < .0 5 ) y e t c o v e r e d th e same a r e a o f th e p a s t u r e (P > .1 0 ) as
t h e o th e r t h r e e b re e d ty p e s . I t i s
in
s tu d y ,
a n im a l m ovem ent. One p o s s ib le
o f d r in k in g .
w e re o b s e r v e d
fr e q u e n tly ,
p o s s ib le t h a t IS IH cows d e m o n s tra te
a n im a ls
C e r ta in a n im a ls ,
to
d r in k
ca n
le s s
d if f e r e n c e
g r a z in g i n
fr e q u e n tly .
c o n s e rv e
e n e rg y
and
c o u ld be
a re a s f a r fro m
By
d r in k in g
m a x im iz e
le s s
p a s tu re
u tiliz a tio n .
A t th e p re s e n t t im e ,
n o t b re e d t y p e
m e a s u r in g
in c lu d e
it
can n o t be d e te rm in e d i f
d iffe r e n c e s in
t h e g r a z in g
e n e rg y e x p e n d itu r e .
th e r e a re o r a re
F u tu re
s tu d ie s ,
b e h a v io r o f co w s g r a z in g r a n g e la n d ,
some e s t im a t io n
o f fo r a g e in t a k e
ra te ,
s lo p e
s h o u ld
u tiliz a tio n
and
fre q u e n c y o f d r in k in g .
W a g ne r ( 1 9 8 5 ) ,
u s in g t h e g r o u p
I cow s fro m
a d ja c e n t p a s tu r e ) , fo u n d s i g n i f i c a n t i n t a k e
fo u r
b re e d ty p e s .
th is
d iffe r e n c e s
The o v e r a ll in t a k e means w e re 2 .3 , 2 .5 ,
s tu d y
( in
an
b e tw e e n t h e
2.6 and 2.8%
B W /d f o r HH, AH, I SI H a nd 3S1H c o w s , r e s p e c t i v e l y . HH cow s consu m e d
le s s fo r a g e
(P<.07) th a n b o th th e IS IH and 3S1H cows b u t n o t le s s th a n
t h e AH c o w s . A t th e p r e s e n t t im e , i t i s
b re e d ty p e d if f e r e n c e s i n
th e c o n d it io n s o f t h i s
g r a z in g
in t a k e
d i f f i c u l t t o a s su m e t h a t t h e
o b s e rv e d by Wagner w o u ld e x i s t und e r
s tu d y . Because o f th e many f a c t o r s in f lu e n c in g
b e h a v io r ( A r n o ld a nd D u d z in s k i, I 97 8 ) , t h e l e v e l o f e n e rg y
e x p e n d itu r e
can ch a n g e f r o m
one e n v ir o n m e n t t o a n o t h e r .
U nder th e
49
c o n d it io n s o f W agner’ s s tu d y ,
a n im a ls w e re g a th e re d on a d a i l y b a s is
and th e n a t u r a l b e h a v io r p a t t e r n s w e re in t e r r u p t e d . How t h i s
t im e
s p e n t g r a z in g ,
d is ta n c e
t r a v e le d
and p a s tu re u t i l i z a t i o n
a ff e c t e d
is
not
k n o w n . F u t u r e s t u d i e s s h o u ld e x a m in e how t h e e x p e r im e n t a l m e th o d s ,
used i n
e s t im a t in g a n im a l in t a k e , in f lu e n c e a n im a l g r a z in g b e h a v io r.
50
SUMMARY
The g r a z in g b e h a v io r o f l a c t a t i n g b e e f cows g r a z in g ra n g e la n d was .
s tu d ie d d u r in g th e summer o f 1984 i n
th e B e a r Paw M o u n ta in s n e a r H avre
M o n ta n a . A t o t a l o f 48 c o w s w e re d i v i d e d i n t o tw o g r o u p s . Each g ro u p
c o n t a in e d
s ix
cow s fro m
th e f o l lo w in g
f o u r b re e d t y p e s : s t r a i g h t
H e re fo r d (HH), 50% Angus-50% H e re fo rd (AH), 50% S im m ental-50% H e re fo rd
(IS IH ) and 75% S im m e n tal-25 %
f o u r g r a z in g
p e r io d s
H e re fo r d
s ta r tin g
on J u ly
(3S1H).
The s tu d y
c o n s is te d
of
22 and e n d in g on A ug u st 30.
The g r a z in g b e h a v io r v a r ia b le s in c lu d e d d a i ly g r a z in g h o u rs , tim e
o f day g r a z in g ,
d is t a n c e t r a v e l e d a n d d i s t r i b u t i o n
b a s ic m o d el f o r a n a ly s is o f th e g r a z in g
o f g r a z in g . The
b e h a v io r v a r i a b l e s in c lu d e d
b r e e d t y p e , g r o u p , p e r i o d ( g r o u p ) , s e x o f c a l f and s i r e b re e d o f c a l f
a s f i x e d m a in e f f e c t s a n d b re e d t y p e
by p e r io d ( g r o u p ) a s t h e m a in
i n t e r a c t i o n . A d d i t i o n s t o t h e d a i l y g r a z in g a nd t i m e o f day g r a z in g
m o d e ls in c l u d e d cow (ra n d o m ) a n d d a y ( f i x e d ) .
p r o d u c tio n ,
cow c o n d i t i o n ,
Cow w e ig h t ,
cow m i l k
c a l f w e ig h t a nd age o f c a l f w e re u se d a s
c o v a r ia t e s w h e ne ve r p o s s ib le t o e xa m in e t h e i r
e ffe c ts
on cow g r a z in g
b e h a v io r .
The
o v e r a ll
d a ily
g r a z in g
m ean w a s
9.4
h r/d .
G r a z in g
tim e
in c r e a s e d f r o m 8 .0 ( p e r io d I ) t o 10 .0 h r / d ( p e r io d 4) d u r in g t h e 4 0 - d
g r a z in g season. No d if f e r e n c e i n
d a i l y g r a z in g h o u rs was fo u n d betw een
t h e f o u r b re e d t y p e s . Age o f th e c a l f a n d l e v e l o f m i l k
p r o d u c t io n
w e re t h e m o st im p o r t a n t (P<.05) c o v a r ia t e s e x p la in in g th e v a r i a t i o n i n
d a ily
g r a z in g h o u rs .
The p a r t i a l r e g r e s s io n
c o e ffic ie n ts f o r
c a l f age
5
1
and m i l k
p r o d u c tio n w e re -.0 2 h r / d / d and .05 h r / d / k g / d ,
The m a j o r i t y
h r.
r e s p e c t iv e ly .
o f g r a z in g to o k p la c e b e tw e e n 600-900 and 1800-2400
AH cows g ra z e d lo n g e r (PC.05) b e tw e e n 900-1200 h r th a n a l l
o th e r b re e d ty p e s .
w e re re c o rd e d
From p e r io d s T t o 4 , in c r e a s e s i n
d u r in g
fiv e
of
th e
3 -h r
d a ily
g r a z in g t im e
t im e
p e r io d s .
G ra z in g t im e d e cre a se d b e tw e e n 3 0 0 -6 0 0 h r and re m a in e d f a i r l y
c o n s ta n t
b e tw e e n 1500-1800 and 2100-2400 h r .
e ig h t
o f th e
The in f lu e n c e
o f m il k
p r o d u c tio n
on t im e s p e n t g r a z in g was m a in ly fo u n d b e tw e e n 2 4 0 0 -3 00 h r.
The o v e r a ll mean d is ta n c e t r a v e le d was 4.7 k m /d . B re e d ty p e was a
s i g n i f i c a n t s o u rc e o f v a r i a t i o n i n
w e re
5 .0 ,
4 .8 ,
r e s p e c tiv e ly .
4.1
a n d 4 .8
d is ta n c e t r a v e le d .
k m /d f o r
HH,
AH,
B reed ty p e means
IS IH
a nd
3S1H
IS IH c o w s t r a v e l e d l e s s t h a n (P < .0 5 ) HH,
c o w s . Cows in c r e a s e d i n
cow s,
AH and 3S1H
d is t a n c e t r a v e l e d f r o m 4 .3 t o 4 .9 k m /d f r o m
p e r io d s I t o 4 and t h i s in c r e a s e f o l l o w e d t h e same g e n e r a l t r e n d a s
d a ily
g r a z in g h o u rs .
o f tr a v e l in
a ll
Two h r / d w e re s p e n t g r a z in g f o r
e v e ry k ilo m e t e r
f o u r o f th e g r a z in g p e r io d s .
The o v e r a ll d i s t r i b u t i o n
mean was 103 h a /c o w .
The p r o p o r t io n
of
t h e p a s t u r e c o v e r e d by e a ch cow ra n g e d f r o m 21 t o 44%. No d i f f e r e n c e
in
d is tr ib u tio n
o f g r a z in g was fo u n d among th e f o u r b re e d ty p e s .
w e ig h t e x p la in e d a s i g n i f i c a n t am ount o f th e v a r i a t i o n i n
C a lf
d is tr ib u tio n
o f g r a z in g . Cows w it h c a lv e s above a v e ra g e i n w e ig h t c o v e re d a g r e a te r
p r o p o r tio n
a v e ra g e
in
o f th e p a s tu r e
w e ig h t
D is t r ib u t io n
(0 .5 h a / k g ) t h a n co w s w i t h
( a d ju s t e d
fo r
cow
body
o f g r a z in g d id n o t in f lu e n c e
c a lv e s b e lo w
c o n d itio n ) .
th e change i n
p r o d u c tio n o r c a l f a verage d a i l y g a in b u t d id s i g n i f i c a n t l y
co w ’ s change i n
b o d y w e ig h t .
Cows g a in e d 0.3 k g i n
cow m il k
a f f e c t " th e
b o d y w e ig h t f o r
52
e v e ry h e c ta r e in c r e a s e above th e a verag e d i s t r i b u t i o n
F rom
v a r ia t io n
th e r e s u lt s
( w i t h i n a b re e d ty p e ) i n
to a v a r ie ty
e n e rg y
m e a s u re d i n
re q u ir e m e n t
a s i g n i f i c a n t a m o u n t o f th e
g r a z in g b e h a v io r can be a t t r i b u t e d
o f c h a r a c t e r is t ic s a s s o c ia te d w it h
B etw een b re e d ty p e s ,
t y p e 's
p re s e n te d h e re ,
o f g r a z in g .
th e cow and th e c a lf .
th e r e seems to be no a s s o c ia t io n b etw e e n
a bre ed
re q u ir e m e n ts and any o f th e g r a z in g b e h a v io r v a r ia b le s
th is
s tu d y .
The b re e d
(HH) s p e n t th e
ty p e w it h
th e
s m a lle s t
same am ount o f t im e g r a z in g ,
e n e rg y
t r a v e le d th e
same d is t a n c e s a nd c o v e r th e same a r e a o f t h e p a s t u r e a s th e b re e d
ty p e
w it h
th e la r g e s t
e n e rg y
r e q u ir e m e n t
(3S1H).
T h is w o u ld in d ic a t e
t h a t t h e in c r e a s e i n t h e m a in te n a n c e r e q u ir e m e n t , due t o th e e n e rg y
c o s t o f g r a z in g and t r a v e l ,
was th e same a c ro s s th e f o u r b re e d ty p e s .
H ow ever, e n e rg y e x p e n d itu r e d if f e r e n c e s amoung th e s e b re e d ty p e s c o u ld
n o t be d e t e r m in e d
a n im a ls
b e c a u s e t h e s lo p e o f t h e t e r r a i n
t r a v e l was n o t m easured.
o v e r w h ic h t h e
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|
■?
I
j'
;■
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"
i
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|
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I
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;
S td b b s ,
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ij
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S
!I
j
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i
i
'
I
.: I
'
J
I
:
1;
!
\
g r a z in g
!
' .I j
W a g n e r, M. W. I 985. F o ra g e i n t a k e a n d m i l k p r o d u c t io n o f r a n g e la n d
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:|
;
11
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■
ij
- j
;;
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i
!f
j
-I
59
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A n i m. S c i . 4 9 :1 4 3 8 .
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a c tiv ity
of
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o f g r a z in g s h e e p i n r e l a t i o n t o h e r b a g e a v a i l a b i l i t y . I .
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APPENDIX
61
T a b le 13. R e s id u a l c o r r e la t io n s b etw e e n g r a z in g b e h a v io r v a r ia b le s and
cow and c a l f t r a i t s 3
T r a it
(2 )
(3 )
(4 )
(5 )
(6 )
(7 )
(8 )
(9 )
D a ily G r a z in g H o u rs ( I ) .07
.12
- .1 5
.18
.02
-.0 7
- .16
- .19
-.0 2
.22
.06
.09
.13
.19
.22
.10
.12
.15
.11
- .17
.01
D is ta n c e T ra v e le d (2 )
D is t r ib u t io n
Cow B od y
(3 )
W e ig h t
M ilk P ro d u c tio n (5 )
C a lf W e ig h t (6 )
Cow C o n d itio n
(7 )
Age o f C a lf (8 )
(4 )
.1 1
. 3 4 * * . 8 9 * * .3 6 *
.2 9 * * .17
- .06
.3 4 *
.10
.3 4 * * . 7 1 * * .06
.27
- .12
o24
Cow H e ig h t (9 )
a The m o d e l used f o r th e a n a ly s is in c lu d e d ; B reed ty p e , P e rio d , Sex o f
c a l f and S i r e b r e e d o f c a l f as f i x e d m a in e f f e c t s . V a r ia b le s h ad
d i f f e r e n t d e g re e s o f fre e d o m and
s ig n if ic a n c e o f each c o r r e la t io n
w a s c a l c u l a t e d s e p a r a t e ly . C
P<.05, * * PC.OI).
62
T a b le 14. R e s id u a l c o r r e la t io n s
o f day g r a z in g 3-
b e tw e e n d a i l y
g r a z in g h o u rs and t im e
T r a it
(2 )
(3 )
(4 )
(5 )
(6 )
(7 )
(8 )
(9 )
D a ily G ra z in g H ours ( I )
.39
.16
.15
.1.6
.26
.14
.22
.37
-.0 5
- .2 7
—.08
.06
.04
-.0 9
.12
-.2 9
-.3 4
.14
.13
.00
-.1 6
. 12
- .2 7
-.1 8
.13
.08
.01
-.2 4
-.1 4
-.0 4
-.1 2
-.2 7
-.1 7
-.11
-.2 7
Tim e o f Day
240 0 -3 00
(2 )
300 -6 0 0
(3 )
600-900
(4 )
900-1200 (5 )
1200-1500 (6 ) •
1500-1800 (7 )
I 800-2100 (8 )
'
-.0 2
2100-2400. (9 )
3 The m o d e l u s e d f o r th e a n a l y s i s i n c l u d e d ; B re e d t y p e , P e r io d , S i r e
b r e e d o f c a l f , S ex o f c a l f as f i x e d m a in e f f e c t s . C o r r e l a t i o n s
( a b s o lu te v a lu e s ) > .1 3 a re s i g n i f i c a n t (P C .0 5 ) .
MONTANA STATE UNIVERSITY LIBRARIES
IlEliKlIlII
3 1 7 6 2 1001 4 4 6 2 3
M ain
$378
L 3L8
c o p .2
,
.
L a t h r o p , W illia m J .
G ra z in g b e h a v io r o f
ra n g e la n d b e e f c o w s ...
M ain
*$378
L3WB
co p .