Grazing behavior of rangeland beef cattle differing in biological type
by Richard Neal Funston
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in
Animal Science
Montana State University
© Copyright by Richard Neal Funston (1987)
Abstract:
A research project was conducted during the summers of 1985 and 1986 at the Northern Montana
Agricultural Research Center to evaluate differences in grazing behavior exhibited by different
lactating beef cow types. The objectives of this project were to measure the major grazing activities
(distance traveled and grazing time) and to analyze possible breed type differences in biting rate. Cows
were fitted with vibracorders and pedometers, and bite rate estimates were recorded throughout the
study period. In 1985, 24 cows were used which consisted of 4 breed groups with 6 cows per breed
group. The breed groups consisted of Hereford (HH), 50% Angus-50% Hereford (AH), 50%
Simmental-50% Hereford (1S1H) and 75% Simmental-25% Hereford (3S1H). Animals grazed on a
320 ha native foothill grassland with slopes from 5-40% dominated by rough fescue, Idaho fescue and
bluebunch wheatgrass on the upland areas and Kentucky bluegrass on the lowland areas. Total daily
grazing hours were 11.8 + .2, 12.3 + .2, 11.6 + .2 and 11.6 + .5 hr/d for HH, AH, 1S1H and 3S1H,
respectively. There was a tendency for AH cows to graze longer than HH and 1S1H (P=.10) but the
AH did not differ from the 3S1H (P>.10). Bite rates were 52.7 + 1.5, 56.2 + 1.5, 53.2 ± 1.4 and 59.0 +
1.6 bites/m for BH, AH, 1S1H and 3S1H, respectively. The 3S1H had a higher bite rate (PC.05) than
the HH and 1S1H but not higher than the AH (P>.1 0). The AH had a higher bite rate (P<.05) than the
1S1H and the HH but the 1S1H and HH did not differ (P>.10). Breed type means for distance traveled
were 3*1 ± .2, 3.4 + .2, 4.0 + .2 and 2.8 + .2 km/d for RH, AH, 1S1H and 3S1H, respectively. The
1S1H cows traveled farther (PC.10) than the other three breed groups. The AH traveled farther than the
3S1H but did not differ from the HH. In 1 986 the breed groups consisted of Hereford (HH),
Tarentaise-Hereford (TH), Tarentaise-Simmental-Hereford (T(SH)) and Charolais-Simmental-Hereford
(C(SH)). The breed groups consisted of 6 lactating cows per group. The pasture was 276 ha and was
similar in terrain and forage composition to the pasture used in 1985. No differences were found in
grazing time among the four breed groups (P>.10). The breed group means were 11.3 + .2, 11.3 + .2,
11.4 + .2, and 11.2 + .2 for BH, TH, T(SH) and C(SH), respectively. Breed group means for bite rate
were 56.9 + 1 .1 , 58.7 ± 1.1 , 60.9 + 1.0, and 59.0 + 1.1 bites/m for BH, TH, T(SH) and C(SH),
respectively. The T(SH) had a higher bite rate than the HH (PC.10) but did not differ from the TH or
C(SH), and the TH and C(SH) did not differ from the HH breed group (P>.10). No differences (P>.10)
were found in distance traveled. Breed group means were 3.5 + .4, 3.8 + .4, 3.6 + .4 and 3.6 +.4 km/d
for BH, TH, T(SH) and C(SH), respectively. These data indicate that grazing time is independent of
breed type. Bite rate does appear to be a behavioral expression that is different among different breed
types. This may be a response that allows different breed types to achieve different intake levels. GRAZING BEHAVIOR OF RANGELAND BEEF CATTLE
DIFFERING IN BIOLOGICAL TYPE
•
by
Richard Neal Funston
A t h e s i s su 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 ire m e n ts f o r th e degree
of
M aster o f S cien ce
in
Animal S cience
MONTANA STATE.UNIVERSITY
Bozeman, Montana
May 1987
MAIN Lib.
y\/3?f
APPROVAL
o f a t h e s i s su b m itted by
R ichard Neal Funston
This t h e s i s h as been read by each member o f th e t h e s i s com m ittee
and h a s b e e n fo u n d t o be s a t i s f a c t o r y r e g a r d i n g c o n t e n t , E n g l i s h
usage, fo r m a t, c i t a t i o n s , b i b l i o g r a p h i c s t y l e , and c o n s is te n c y , and i s
ready f o r subm ission t o th e C ollege o f Graduate S t u d i e s .
S -/M / 8 7
D a te
__________
cQ
B
C h a i r p e r s o n , Graduate Committee
Approved f o r th e Major Department
5 » ~ ~3—(b ~ ^ ^
Date
Head, Major Department
Approved f o r th e C ollege o f Graduate S tu d ie s
Date
__________
Graduate Dean
iii
STATEMENT OF PERMISSION TO USE
In p r e s e n t i n g t h i s
th e sis
in
p a rtia l
fu lfillm e n t
of
th e
r e q u i r e m e n t s f o r a m a s t e r ' s d e g r e e a t M ontana S t a t e U n i v e r s i t y , I
a g r e e t h a t t h e l i b r a r y s h a l l make i t a v a i l a b l e t o b o r r o w e r s u n d e r
r u l e s o f th e l i b r a r y .
B r ie f q u o ta tio n s from t h i s t h e s i s a r e a llo w a b le
w ith o u t s p e c i a l p e rm is s io n , pro v id ed t h a t a c c u r a te acknowledgement o f
so u rce i s made.
P e rm is s io n f o r e x te n s iv e q u o ta tio n from o r r e p r o d u c tio n o f t h i s
t h e s i s may be g ra n te d by my m ajor p r o f e s s o r , o r i n h i s a b sen ce, by th e
D ir e c to r o f L i b r a r i e s when, in t h e o p in io n o f e i t h e r , t h e proposed use
o f th 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 rp o ses.
Any copying o r use of th e
m a t e r i a l i n t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d
w ith o u t my w r i t t e n p e rm issio n .
S ig n a tu r e G^ZpJ vha D
Date
S-Ak-Sl
-^U yi/vv^/v
t
iv
ACKNOWLEDGEMENTS
T h is
th e sis
is
n o t th e
re su lt
o f one p e r s o n ,
it
is
accom plishm ent o f a g ra d u a te s tu d e n t and s e v e r a l o t h e r people.
th e
This
s e c t i o n o f t h e t h e s i s i s t o th a n k e v e r y o n e who h a s h e l p e d me i n t h e
l a s t tw o y e a r s o f g r a d u a t e s c h o o l .
professor,
I w o u ld l i k e t o t h a n k my m a jo r
Don K ress who gave me th e o p p o rtu n ity t o come t o g ra d u a te
s c h o o l and a l s o g u id e d me i n my r e s e a r c h and c l a s s e s .
A n o th e r v e r y
im p o r ta n t p erso n I would l i k e t o thank i s K ris Havstad who guided me
i n my r e s e a r c h and t a u g h t me some i m p o r t a n t t h i n g s a b o u t r a n g e and
k e p t me g o i n g w h e n I t h o u g h t t h e r e w a s l i t t l e
hope.
B e ra rd in e lli
much f o r y o u r
and P e t e B u r f e n i n g ,
th a n k you v e r y
To J i m
a s s i s t a n c e and a p p r e c i a t i o n o f s c ie n c e w h ile my major p r o f e s s o r was on
sab b a tic al.
To Kathy Hanford, S teve Kachman and Mike McInerney thank
you f o r your a s s i s t a n c e i n t h e e v e r c o n fu sin g world o f s t a t i s t i c s .
Dan D o o rn b o s and a l l
Research C en ter
To
o f t h e p e o p le a t t h e N o r t h e r n A g r i c u l t u r a l
thank you f o r a l l your h e lp and c o o p e r a tio n w ith my
r e s e a r c h , w ith o u t your c o o p e ra tio n t h i s r e s e a r c h could n o t have been
accom plished.
To Web and C h a r o le t te Thackeray, thank you f o r l e t t i n g
us conduct o u r r e s e a r c h on your la n d and thank you f o r making us f e e l
so welcome.
To Ed F r e d r ic k s o n , my r e s e a r c h p a r t n e r , thank you f o r a l l
your h e lp and a s s i s t a n c e .
I would a l s o l i k e t o thank a l l o f my f e llo w
g ra d u a te s tu d e n t s and th e s e c r e t a r i e s o f th e d e p artm en t f o r making my
s ta y h e re an e n jo y a b le one.
F i n a l l y I would l i k e t o thank my w ife f o r
bein g so u n d e rs ta n d in g th e s e l a s t two y e a r s .
V
TABLE OF CONTENTS
Page
vi
LIST OF TABLES..................................
xLIST OF FIGURES ...............................................................................................................v i i
ABSTRACT...............................................................................................
v iii
I
LITERATURE R E V IE W ..........................
2
OO U l IV)
INTRODUCTION ..................................................................................................................
Animal F a c to r s . . .
Range F a c t o r s
. . .
Environmental F a c to r s
MATERIALS AND METHODS'........................................................
11
RESULTS AND DISCUSSION.....................................................................................
18
1985 P ro d u ctio n C h a r a c t e r i s t i c s ............................................................. 18
Time Spent Grazing . . . . . .
.............................................................
20
Time o f Day G r a z i n g .............................................................
22
B ite R a t e ......................................................................................................... • 24
26
D is ta n c e T rav eled .......................................
1986 P ro d u c tio n C h a r a c t e r i s t i c s ..........................
27
Time Spent Grazing ........................................................................................3 1
Time o f Day G r a z i n g .......................... - ..........................................................34
B ite Rate .............................................................
35
D is tan c e T r a v e l e d ....................................................................................... • 37
S p e c u la tio n and F u tu re D i r e c t i o n ............................................................
39
SUMMARY................................................................
LITERATURE C IT E D ...........................................................................................
[
43
• • •
46
vi
LIST OF TABLES
Table
Page
1.
L e 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 eight (BW),
c a l f w eight (CW) and m ilk p r o d u c tio n (MP) (1985) . . . . . .19
2.
L e a s t- s q u a r e s means and s ta n d a rd e r r o r s f o r cow body w eight
(BW), c a l f w eight (CW) and m ilk p ro d u c tio n (MP) (1985) . . .19
3-
L e a s t- s q u a r e s a n a l y s i s o f v a r ia n c e f o r t o t a l d a i l y
g r a z in g tim e (1985) ..................................
21
L e a s t- s q u a r e s a n a l y s i s o f v a r ia n c e f o r time o f day
g r a z in g ( 1 9 8 5 ) .....................
.24
4.
5.
6.
7.
L e a s t- s q u a r e s
a n a l y s i s o f v a r ia n c e f o r b i t e r a t e (1985) . . . .27
L e a s t- s q u a r e s a n a l y s i s 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
(1985) .............................................................. . . . . . . .
..................29
L e a s t- s q u a r e s a n a ly s e s o f v a ria n c e f o r cow body w eight (BW),
c a l f w eight (CW) and m ilk p ro d u c tio n (MP) (1986)
30
8.
L g a s t-s q u a r e s means and s ta n d a r d e r r o r s f o r cow body weight
(BW), c a l f w eight (CW) and milk p ro d u c tio n (MP) (1986) . . .31
9.
L e a s t- s q u a r e s a n a l y s i s o f v a ria n c e f o r t o t a l d a i l y
g ra z in g time ( 1 9 8 6 ) ....................................................
32
10.
Forage a v a i l a b i l i t y (DM) f o r g r a s s e s , fo r b s and sh ru b s (1986) .34
11.
L e a s t- s q u a r e s a n a l y s i s o f v a r ia n c e f o r time o f day
g r a z in g (1986)
34
12.
L e a s t- s q u a r e s
a n a l y s i s o f v a r ia n c e f o r b i t e r a t e (1986) . . . .37
13.
L e a s t- s q u a r e s
(1986)
a n a l y s i s 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
39
vii
LIST OF FIGURES
F ig u re
Page
1 . Map o f p a s tu r e d u rin g 1985 .......................................
12
2.
Map o f p a s t u r e d u rin g 1986 ............................................................................ 16
3.
E f f e c t o f day o f th e y e a r on t o t a l d a i l y g ra z in g time d u rin g
1985 ................................
................................................ ....
23
25
4.
Time o f day g ra z in g d u rin g 1985
5.
E f f e c t o f day o f th e y e a r on b i t e r a t e d u rin g 1985 . . . . . .
6.
E f f e c t o f day of th e y e a r on t o t a l d a i l y g r a z in g time d u rin g
1986 . ................................................................................ . ........................... 33
7.
Time o f day g ra z in g d u rin g 1986
36
8.
E f f e c t o f day o f t h e y e a r on b i t e r a t e d u rin g 1986 . . . . . .
38
28
v iii
ABSTRACT
A r e s e a r c h p r o j e c t was conducted d u rin g th e summers o f 1985 and
1986 a t th e N o rth ern Montana A g r i c u l t u r a l Research C en ter t o e v a lu a te
d i f f e r e n c e s i n g ra z in g b e h a v io r e x h ib ite d by d i f f e r e n t l a c t a t i n g b eef
cow ty p e s. The o b j e c t i v e s o f t h i s p r o j e c t were t o measure th e m ajo r
g r a z in g a c t i v i t i e s (d is ta n c e t r a v e l e d and g ra z in g tim e ) and t o a n aly ze
p o s s ib le b reed ty p e d i f f e r e n c e s i n b i t i n g r a t e . Cows w ere f i t t e d w ith
v i b r a c o r d e r s and p e d o m e t e r s , and b i t e r a t e e s t i m a t e s w e re r e c o r d e d
th ro u g h o u t th e stu d y p e rio d .
I n 1985, 24 cows w e re u s e d w h ic h
c o n s i s t e d o f 4 b r e e d g r o u p s w i t h 6 cow s p e r b r e e d g r o u p . The b r e e d
g r o u p s c o n s i s t e d o f H e r e f o r d (HH), 50% Angus-50% H e r e f o r d (AH), 50%
S im m en ta l-5 0 % H e r e f o r d (TSIH) and 75% Simmental-25% H ereford (3S1H).
Animals g razed on a 320 ha n a t i v e f o o t h i l l g r a s s la n d w ith s lo p e s from
5-40% dom inated by rough fe s c u e , Idaho fe s c u e and bluebunch w h e atg rass
on t h e u p la n d a r e a s and K e n tu ck y b l u e g r a s s on t h e l o w l a n d a r e a s .
T o t a l d a i l y g r a z i n g h o u r s w e re 11.8 + .2 , 12.3 + .2 , 11.6 + .2 and
11.6 + .5 h r / d f o r HH, AH, ISIH and 3S1H, r e s p e c t i v e l y . T h e re was a
te n d e n c y f o r AH cow s t o g r a z e l o n g e r t h a n HH and ISIH (P=.10) b u t t h e
AH d i d n o t d i f f e r fro m t h e 3S1H (P>.10). B i t e r a t e s w e r e 52.7 + 1 .5 ,
56.2 + 1 .5 , 53-2 ± 1.4 and 59.0 + 1.6 b i t e g / m f o r BH, AH, ISIH and
3S1H, r e s p e c t i v e l y . The 3S1H h ad a h i g h e r b i t e r a t e (P<.05) t h a n t h e
HH and ISIH b u t n o t h i g h e r t h a n t h e AH (P>.1 0 ). The AH had a h i g h e r
b i t e r a t e (PC.05) th a n th e ISIH and th e HH bu t th e ISIH and HH d id n o t
d i f f e r (PXIO). Breed ty p e means f o r d is ta n c e t r a v e l e d w ere 3*1 ± .2,
3.4 + .2 , 4.0 + .2 and 2.8 + .2 k m /d f o r RH, AH, ISIH and 3S1H,
re sp ec tiv e ly .
The ISIH cows t r a v e l e d f a r t h e r (PC.10) th a n th e o th e r
th r e e breed groups. The AH t r a v e l e d f a r t h e r th a n th e 3S1H b u t d id n o t
d i f f e r fro m t h e HH. I n I 986 t h e b r e e d g ro u p s , c o n s i s t e d o f H e r e f o r d
(HH), T a re n ta is e -H e re fo rd (TH), T a r e n t a i s e - S i m m e n t a l - H e r e f o r d (T(SH))
and C h a ro la is-S im m e n ta l-H e re fo rd (C(SH)). The b reed groups c o n s is te d
o f 6 l a c t a t i n g cows p e r group; The p a s tu r e was 276 ha and was s i m i l a r
i n t e r r a i n and f o r a g e c o m p o s i t i o n t o t h e p a s t u r e u s e d i n 1985. No
d i f f e r e n c e s w e re fo u n d i n g r a z i n g t i m e among t h e f o u r b r e e d g r o u p s
(P X 1 0 ) . The b r e e d g ro u p m eans w e re 1 1.3 + .2, 1 1 .3 + .2 , 11.4 + .2 ,
and 11.2 + .2 f o r BH, TH, T(SH) and C(SH), r e s p e c t i v e l y . B reed g ro u p
m eans f o r b i t e r a t e w e re 56.9 + 1 .1 , 58.7 ± 1.1 , 60.9 + 1 .0 , and 59.0
+ 1.1 b i t e s / m f o r BH, TH, T(SH) and C(SH), r e s p e c t i v e l y .
The T(SH)
had a h ig h e r b i t e r a t e th a n t h e HH (PC.10) bu t did n o t d i f f e r from th e
TH o r C(SH), and t h e TH and C(SH) d i d n o t d i f f e r fro m t h e HH b r e e d
g r o u p (P>.1 Q).
No d i f f e r e n c e s ( P X I O ) w ere f o u n d i n d i s t a n c e
t r a v e l e d . B reed g ro u p m eans w e re 3.5 + .4 , 3.8 + .4 , 3.6 + .4 and 3.6
+.4 k m /d f o r BH, TH, T(SH) and C(SH), r e s p e c t i v e l y .
These d a t a
i n d i c a t e t h a t g ra z in g tim e i s in d ep en d en t o f b reed ty p e .
B ite r a t e
d o e s a p p e a r t o be a b e h a v i o r a l e x p r e s s i o n t h a t i s d i f f e r e n t among
d i f f e r e n t b reed ty p e s . T h is may be a re sp o n se t h a t a llo w s d i f f e r e n t
b reed ty p e s t o a c h ie v e d i f f e r e n t in ta k e l e v e l s .
I
INTRODUCTION
Rangelands a re one o f th e N orthern G reat P l a i n s l a r g e s t renew able
re s o u r c e s and i t i s p r i m a r i l y through b e ef c a t t l e p ro d u c tio n t h a t we
a ch ie v e an economic g a in from t h e s e r a n g e l a n d s .
In te n siv e research
a d d r e s s i n g t h e i n t e r f a c e o f b e e f c a t t l e and r a n g e l a n d s i s o f g r e a t
i m p o r t a n c e t o t h o s e who u t i l i z e r a n g e l a n d f o r b e e f p r o d u c t i o n .
I d e n t i f i c a t i o n o f th o se b re e d s o r b reed ty p e s t h a t e x h i b i t a
g r a z in g b e h a v io r f a v o r a b le to th e e f f i c i e n t u t i l i z a t i o n o f range
fo ra g e w a r r a n ts f u r t h e r i n v e s t i g a t i o n .
S q u ire s (1978) has emphasized
t h a t d a ta on g e n e r a l range l i v e s t o c k b e h a v io r i s a v a i l a b l e bu t l i t t l e
a tte n tio n
has
been
g iv e n
td
th e
re la tio n sh ip
a c t i v i t i e s and su b seq u en t anim al perform ance.
of
free
ra n g in g
To more f u l l y e x p l o i t
p ro d u c tio n o f b e e f cows on ra n g e la n d , a more com plete u n d e rs ta n d in g o f
t h e i r fe e d in g a c t i v i t i e s i s e s s e n t i a l .
d a ta
w ould p r o v i d e
in fo rm atio n
to
The c o l l e c t i o n o f b e h a v io ra l
c o m p le m en t
e x ten siv e
a n im a l
p e r f o r m a n c e d a t a c u r r e n t l y b e i n g g e n e r a t e d by c o o p e r a t i n g M ontana
A g r i c u l t u r a l Experim ent S t a t i o n p r o j e c t s i n anim al b re e d in g and range
n u tritio n .
The m a j o r o b j e c t i v e o f t h i s s t u d y was t o e v a l u a t e t h e g r a z i n g
b e h av io r and p ro d u c tio n c h a r a c t e r i s t i c s (cow w e ig h t, c a l f w eight and
m ilk p ro d u c tio n ) o f g e n o ty p ic a lly 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
g r a z i n g summer r a n g e l a n d .
The g r a z i n g b e h a v i o r a c t i v i t i e s s t u d i e d
w ere tim e s p e n t g ra z in g , d is ta n c e t r a v e l e d and b i t e r a t e .
2
LITERATURE REVIEW
The f o c u s
re la tio n sh ip
of
of
th is
g ra z in g
lite ra tu re
an im a l
re v ie w
response
to
is
to
e x am in e
a n im a l,
ra n g e
th e
and
e n v iro n m e n ta l f a c t o r s .
Animal F a c to r s
G r a z in g b e h a v i o r a l p a t t e r n s h a v e b e en shown t o be
a f f e c t e d by
genotype and p h y s io lo g ic a l s t a t u s o f th e g r a z in g an im a l.
In a y e a r round s tu d y , Herbel and Nelson (1966) r e p o r te d H ereford
cow s g r a z e d 1.4 h r / d l o n g e r , w a lk e d 1.3 h r / d l e s s and t r a v e l e d 4.7
km/d l e s s , th a n S an ta G e r tr u d is cows on New Mexico ra n g e lan d (PC.05).
The H e re fo rd 's in c r e a s e d g ra z in g tim e was a t n ig h t. Y eates and Murray
(1966) c o n d u c te d w a l k i n g t r i a l s w i t h H e r e f o r d and S a n t a G e r t r u d i s
c a ttle
i n A u s t r a l i a and fo u n d t h a t t h e S a n t a G e r t r u d i s had l e s s
in c r e a s e i n r e c t a l te m p e ra tu re and r e s p i r a t o r y r a t e th a n th e Hereford
c a t t l e i n te m p e r a tu r e s ra n g in g from 27 t o 29 C.
I t was su g g ested t h a t
t h e S a n t a G e r t r u d i s c a t t l e w e re more h e a t t o l e r a n t and had
a lo w e r
e x e r c is e h e a t p ro d u c tio n . This was p ro b ab ly a s s o c i a t e d w ith a lo n g e r
w a lk in g s t r i d e .
T his in c re a s e d h e a t t o le r a n c e en ab le d th e S a n ta
G e r t r u d l s c a t t l e t o a d a p t b e t t e r t o h o t c l i m a t e s and t r a v e l l o n g e r
d istan ces.
In a stu d y done on a r i d ra n g e la n d s i n New Mexico, Anderson
(1986) fo u n d t h a t H e r e f o r d cows t r a v e l e d s i g n i f i c a n t l y l e s s (P<.04)
th a n H ereford X S a n ta G e r tr u d is cows, 6.9 and 7-3 km/d,
re sp ec tiv e ly .
S t u d i e s c o m p a r in g b r e e d s o f t h e same s p e c i e s h a v e shown l i t t l e
d i f f e r e n c e s i n g ra z in g a c t i v i t i e s .
In a stu d y conducted i n New York
u s in g one H ereford and t h r e e Angus cows, J o h n s to n e -WalI ace and Kennedy
3
( 1944) r e p o r t e d b o th b r e e d s s p e n t fro m 7 t o 8 h r o u t o f 24 g r a z i n g , 7
h r c h e w in g t h e i r c u d , had a b i t e r a t e fro m 50 t o 7 0 b i t e s / m i n and
t r a v e l e d an a v e r a g e o f 4 .02 km /d on p a s t u r e s r a n g i n g fro m 1.2 t o 2.8
ha.
Kropp e t a l . ( I 973) c o n d u c te d a s t u d y i n Oklahoma on b e h a v i o r o f
n o n l a c t a t i n g h e i f e r s and c o n c lu d e d t h a t t h e b e h a v i o r p a t t e r n s and
c o n c u rre n t w eig h t g a in s o f H o l s t e i n and H e r e f o r d X H o l s t e i n h e i f e r s
w e re s i m i l a r t o H e r e f o r d h e i f e r s i n ra n g e b e h a v i o r a c t i v i t i e s o f
g ra z in g , r u m in a tin g , i d l i n g , d r in k in g , w a lk in g and s le e p in g .
Lathrop
( 1985) s t u d i e d f o u r l a c t a t i n g b e e f c a t t l e t y p e s , H e r e f o r d (HH), 50%
Angus - 50% H ereford (AH), 50% Sim m ental - 50% H ereford (1S1H) and 75%
S im m e n ta l - 25% H e r e f o r d (3S1H), i n n o r t h e r n M ontana and fo u n d no
d i f f e r e n c e s i n g r a z i n g ti m e b u t d i d d i s c o v e r t h a t t h e ISIH cows
t r a v e l e d l e s s (P<.05)
w e re 5 .0 ,
4 .8 ,
t h a n BH, AH and 3S1H cow s.
4.1 and 4.8 km /d f o r HH, AH,
B re ed t y p e m eans
ISIH and 3S1H co w s,
re sp ec tiv e ly .
S t r i c k l i n e t a l . (1976) conducted a study comparing Angus (A) and
C h a r o l a i s X Angus (CXA) c r o s s cow s a n d fo u n d t h e CXA cow s on summer
p a s t u r e g r a z e d an a v e r a g e o f 9.0 h r / d and t h e A cow s g r a z e d 8.5 h r / d
(P<.01).
T h ese d i f f e r e n c e s may be a f u n c t i o n
of d iff e r e n t
p r o d u c t i o n r a t h e r t h a n an i n h e r e n t b reed d i f f e r e n c e .
Lathrop (1985)
r e p o r te d in c r e a s e d g ra z in g tim e w ith in c r e a s e d m ilk p ro d u c tio n ,
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 was .05 h r / d / k g / d .
a tendency f o r h ig h m ilk p ro d u c e rs to s a t i s f y
by in c r e a s in g n i g h t t i m e
g ra z in g
m ilk
th e
Stobbs (1970) n o te d
t h e i r n u t r i t i o n a l needs
on t r o p i c a l g r a s s la n d s i n A u s t r a l i a .
A p o s i t i v e r e l a t i o n s h i p between g r a z in g tim e and m ilk p ro d u c tio n was
a l s o r e p o r te d i n both J e r s e y and F r i e s i a n d a ir y c a t t l e (Brumby, 1959).
4
In ta k e
c o rre la ted .
medium
and g r a z i n g
tim e
do n o t a p p e a r t o
be p o s i t i v e l y
Zoby and Holmes (1983) s t u d ie d g ra z in g b e h a v io r i n s m a l l,
and l a r g e
fram e groups o f B r i t i s h F r ie s a n
c a ttle
w h ic h
c o n s i s t e d o f 6 d r y n o n p r e g n a n t cow s and 2 l a r g e s t e e r s i n t h e l a r g e
g r o u p , 8 s t e e r s i n t h e medium g r o u p and 8 s t e e r c a l v e s i n t h e s m a l l
group w ith mean l i v e w e ig h ts o f 631, 439 and 164 kg f o r l a r g e , medium
and s m a l l a n i m a l s , r e s p e c t i v e l y .
G ra z in g t i m e and b i t e r a t e was
h i g h e s t f o r s m a ll c a t t l e and lo w e s t f o r la r g e c a t t l e .
I n ta k e and b i t e
s i z e f o llo w e d an o p p o s ite tr e n d w ith th e la r g e a n im a ls h a v in g t h e
h i g h e s t in t a k e and b i t e s i z e and th e s m a ll a n im a ls h av in g th e lo w e s t.
Forage a v a i l a b i l i t y ranged from 1,930 to 5,270 k g /h a .
Hendricksen and
Minson (1980) a ls o r e p o r te d a s i g n i f i c a n t l i n e a r r e l a t i o n s h i p (r^=.88)
b e tw e e n i n t a k e and b i t e s i z e b u t i n t a k e d id n o t h a v e a s i g n i f i c a n t
l i n e a r r e la tio n s h ip w ith b i t e
g r a s s la n d s o f A u s t r a l i a .
ra te
or g ra z in g
t i m e on t r o p i c a l
Wagner e t a l . (1986) found d i f f e r e n t (P<.01)
i n t a k e l e v e l s , 2 .3 , 2 . 5 , 2.6 and 2.8% BW/d f o r BH, AH, ISIH and 3S1H
b e e f cows, r e s p e c t i v e l y .
Lathrop (1985), u sin g t h e same b reed ty p e s
found no a p p a re n t d i f f e r e n c e s i n g r a z in g tim e , s u p p o rtin g th e p re v io u s
s t u d i e s showing no r e l a t i o n s h i p betw een i n ta k e and g r a z in g tim e .
In a
study u s in g n o n l a c t a t i n g H e r e f o r d , H o l s t e i n X H e r e f o r d a n d H o l s t e i n
h e i f e r s Kropp e t a l . (1973) concluded t h a t g ra z in g ti m e was n o t h ig h ly
r e l a t e d to fo ra g e in ta k e because i n each season th e b re e d w ith th e
h ig h e s t g r a z in g tim e g a in ed t h e l e a s t w e ig h t.
C hacon and S to b b s
( 1 976) s t u d i e d c o r r e l a t i o n s b e tw e e n e s t i m a t e d i n t a k e a n d . e a t i n g
b e h a v io r m easurem ents and r e p o r te d t h a t th e m ajor f a c t o r i n f l u e n c i n g
e s t i m a t e d i n t a k e was b i t e s i z e .
I n ta k e was e s t i m a t e d from th e p ro d u ct
5
o f th e mean b i t e r a t e i n n o n - f i s t u l a t e d cows and th e mean b i t e s i z e o f
f i s t u l a te d cows ta k en i n a 2 4 -h r p e rio d .
Range F a c to r s
Feed i n t a k e o f g r a z i n g a n i m a l s i s
a f u n c t i o n o f tim e s p e n t
e a t i n g , b i t e r a t e and b i t e s i z e (Chacon e t a l . , I 97 6 ).
G ra z in g t i m e
and b i t e r a t e a r e f u n c t i o n s o f many p a s t u r e v a r i a b l e s (Chacon and
S t o b b s , I 976).
Some o f t h e v a r i a b l e s s t u d i e d by Chacon and S to b b s
(I 976) i n c l u d e p a s t u r e y i e l d , % l e a f , l e a f s te m r a t i o and h e i g h t o f
fo rag e.
S tu d ie s in v o lv in g s p e c i f i c p a s t u r e p a r a m e te r s have been
in c o n c lu siv e
( A r n o l d , 1981; A rn o ld and D u d z i n s k i , I 967 a , b ) .
s e c t i o n w i l l e m p h a s iz e
T h is
a v a i l a b i l i t y , a g r o s s m e a s u r e o f amount o f
f o r a g e w h ic h i n c l u d e s many o f t h e p a r a m e t e r s w h ic h a r e n o t w e l l
u n d e rsto o d .
G r a z i n g a n i m a l s c an p a r t i a l l y com pensate
a v a i l a b i l i t y by Changing t h e i r g ra z in g b eh av io r.
f o r d e c l i n i n g fo ra g e
Jam ieso n and Hodgson
(1979) found t h a t as g reen herbage mass was m e c h a n ic a lly reduced from
3,000 t o 1,000 kg OM/ h a, b i t i n g r a t e s and g ra z in g tim e o f c a lv e s and
lambs in c r e a s e d but i n s u f f i c i e n t l y to o f f s e t th e d e c l i n e i n b i t e s i z e .
I n t a k e d e c l i n e d by 24% and 39% f o r c a l v e s and l a m b s , r e s p e c t i v e l y .
Chacon and Stobbs (1976) r e p o r te d t h a t b i t i n g r a t e i n c a t t l e in c re a s e d
sig n ific a n tly
(P<.05) fro m 56 t o 62.4 b i t e s / m i n and 51.4 t o 59.4
b i t e s / m i n as a v a i l a b l e fo ra g e d e c re a se d from 7,200 t o 1 ,500 k g /h a and
3,900 t o 2,400 k g /h a , r e s p e c t i v e l y .
Grazing tim e a ls o in c re a s e d from
550 t o 650, m in /d and 525 t o 600 m i n / d , r e s p e c t i v e l y . At l o w e r f o r a g e
a v a ila b ility ,
g ra z in g
tim e ,
b ite
ra te
and b i t e
siz e
d e c lin e d ,
r e s u l t i n g i n l o w e r e d f o r a g e i n t a k e . Peak g r a z i n g t i m e and h i g h e s t
6
number o f b i t e s o c c u rre d when l e a f y i e l d s averaged 1,000 kg DM/ha.
th e l a t e r s t a g e s o f d e f o l i a t i o n ,
s iz e d e c lin e d ,
g r a z in g tim e ,
In
e a t i n g b i t e s and b i t e
r e s u l t i n g in a lo w e r in ta k e l e v e l .
A ll d e n (1970)
fo u n d t h a t a t g r e a t e r t i l l e r l e n g t h s t h e s i z e o f b i t e and r a t e o f
b i t i n g in sheep v a rie d in v e r s e ly
in ta k e .
to m a in ta in a c o n sta n t r a t e of
When a c c e s s i b i l i t y o f h erb ag e imposed l i m i t a t i o n s on th e r a t e
a t w h ic h t h e a n i m a l was a b l e t o p r e h e n d i t s f o o d , s h e e p p a r t i a l l y
compensated f o r t h e reduced amount o f fo ra g e by an i n c r e a s e i n g r a z in g
t i m e (fro m 6 t o 13 h r / d ) .
H ow ever, a s an a n i m a l e x t e n d e d i t s p e r i o d
o f g r a z i n g t h e c o m p e n s a tio n becam e p r o g r e s s i v e l y m o re i n c o m p l e t e .
A l l d e n (1970) r e p o r t e d a r e l a t i v e l y
c o n sta n t r a t e
o f i n t a k e and
g r a z i n g t i m e a t f o r a g e a v a i l a b i l i t y g r e a t e r t h a n 3 , OpO k g / h a , b u t a
f o u r f o l d d e c re a se i n in ta k e and a tw o fo ld in c r e a s e i n g r a z in g tim e was
o b s e r v e d a s f o r a g e a v a i l a b i l i t y d e c l i n e d fr o m 3 ,0 0 0 t o 500 k g / h a .
Zoby and H olm es (1983) r e p o r t e d s i g n i f i c a n t l y h ig h e r (P<.05) g ra z in g
tim e and b i t e r a t e , 9.25 h r / d and 68.6 b i t e s / m i n , r e s p e c t i v e l y , under
low fo ra g e a v a i l a b i l i t y , 2,140 kg DM/ha, when compared t o g ra z in g tim e
and b i t e r a t e , 8.4 h r / d and 59.8 b i t e s / m i n , r e s p e c t i v e l y , under h ig h e r
fo ra g e a v a i l a b i l i t y , 4,470 kg DM/ha.
Few s t u d i e s h a v e b e e n r e p o r t e d
on t h e b e h a v i o r a l r e s p o n s e t o
f o r a g e a v a i l a b i l i t y l e s s t h a n I ,000 k g / h a . As a s t a n d i n g c r o p o f
c r e s t e d w heat g r a s s was grazed by Angus h e i f e r s from 417 to 203 kg d ry
m a t t e r / h a , g r a z i n g t i m e i n c r e a s e d fr o m 458 t o 602 m i n / d , and b i t i n g
r a t e i n c r e a s e d fro m 54 t o 63 b i t e s / m i n ( S c a r n e c c h i a e t a l . , 19 8 5 ).
When p a s t u r e y i e l d s a r e low , b i t e s i z e l i m i t e d a n im a ls from a c h ie v in g
maximum fo ra g e in ta k e (Stobbs,
1973), and when m a tu re p a s t u r e y i e l d s
7
a r e h ig h maximum fo ra g e in ta k e was n o t ach iev ed due t o d i f f i c u l t y i n
h a r v e s t i n g enough f o r a g e which r e s u l t e d i n long g r a z in g tim e s (S tobbs,
1970). . In ta k e p e r hour o f g r a z in g d e c re a se d r a p i d l y a s g ra z in g tim e
i n c r e a s e d on p a s t u r e s o f low a v a i l a b i l i t y and l o w e r i n t a k e p e r b i t e
w as n o t f u l l y c o m p e n s a te d by an i n c r e a s e i n b i t i n g r a t e (A rn o ld ,
1964).
One f a c t o r which may l i m i t b e h a v io r a l re s p o n s e s and su b sequent
in ta k e i s f a tig u e .
S to b b s (1975) r e p o r t e d f a t i g u e l i m i t s a t 720
m in u te s o f g ra z in g and 36,000 b i t e s i n a 24 %r p e rio d .
G razing tim e s
re p o r te d by S c a rn e c c h ia e t a l . (1985) were 90.4$ o f t h e f a t i g u e l i m i t s
r e p o r te d by Stobbs (1975).
F o r a g e a v a i l a b i l i t y a l s o a f f e c t s t h e d i s t a n c e t r a v e l e d by t h e
g ra z in g a n im a l.
Q uinn and H e rv ey (1970) r e p o r t e d t h a t i n l i g h t l y
g ra z ed 20.2 ha p a s t u r e s , y e a r l i n g c a t t l e averaged 2.8 km/d compared t o
3.7 km/d i n m oderate and h e a v il y g ra z ed p a s tu r e s .
The l e s s e r amount
o f t r a v e l i n t h e l i g h t - u s e p a s t u r e appeared t o be t h e r e s u l t o f more
a v a i l a b l e fo r a g e . Though d i s t a n c e s were s i m i l a r , th e p a t t e r n of t r a v e l
d i f f e r e d betw een m oderate and h e a v i l y grazed p a s t u r e s . The s t e e r s i n
m o d e ra tely g ra z ed p a s t u r e s s p e n t more tim e ly in g down b u t t h e i r h ig h
amount o f t r a v e l was due t o a f a i l u r e t o g ra z e when moving t o w a te r or
from one a r e a to a n o th e r.
The s t e e r s on th e h e a v i l y g ra z e d p a s t u r e s
s p e n t more tim e g r a z in g because t h e fo ra g e was n o t a s abundant a s i n
t h e o t h e r p a s t u r e s . P e t e r s o n and W o o lfo lk (1955) d i s c o v e r e d s i m i l a r
r e s u l t s f o r H ereford cows under d i f f e r e n t fo ra g e a v a i l a b i l i t y .
Areas
w i t h h i g h e r a v a i l a b l e f o r a g e h ad l e s s t r a v e l t h a n a r e a s w i t h l o w e r
forage a v a i l a b i l i t y .
Under two. d i f f e r e n t g r a z i n g s y s t e m s , h i g h -
in t e n s i t y - l o w - f r e q u e n c y (HILF) and c o n t i n u o u s g r a z i n g , A n d e rso n and
8
Kothmann (1980) r e p o r te d t h a t H ereford h e i f e r s under th e HILF t r a v e l e d
1.6 km /d l e s s (P<.05) t h a n t h e a n i m a l s u n d e r c o n t i n u o u s g r a z i n g . The
HILF c o n s i s t e d
of fiv e
4 - h a p a d d o c k s and t h e
c o n s is te d o f one 20-ha paddock.
c o n t i n u o u s s y s te m
Crude p r o t e i n and d i g e s t i b l e energy
w e re t h e common i n d e p e n d e n t v a r i a b l e s t h a t c o r r e l a t e d w i t h a n im a l
t r a v e l r e g a r d l e s s o f t h e t y p e o f g r a z i n g m an ag em en t.
W alk e r e t a l .
(1985) found t h a t c a t t l e under s h o r t d u r a tio n g ra z in g ten d ed t o walk
f a r t h e r w ith
more a n i m a l v a r i a t i o n t h a n a n i m a l s on a c o n t i n u o u s
g ra z in g system .
The p a s t u r e s i n t h i s e x p erim en t were from 28 to 39 ha
i n t h e s h o r t d u r a t i o n g r a z i n g s y s t e m s and .242 h a i n t h e c o n t i n u o u s
g r a z in g sy ste m .
D i f f e r e n c e i n t r a v e l u n d e r t h e s e tw o s y s t e m s was
p r o b a b l y due t o f o r a g e a v a i l a b i l i t y and n o t p a s t u r e s i z e a s i n t h e
ex p erim en t conducted by Anderson and Kothmann (1980).
Environm ental F a c to r s
The environm ent o f th e g ra z in g anim al may in f l u e n c e i t s g ra z in g
b eh av io r.
Tem perature and h u m id ity a f f e c t th e p h y sio lo g y o f a n im a ls
and t h u s i n f l u e n c e
th e ir a c tiv itie s
in c lu d in g g ra z in g b e h a v io r.
E h ren reic h and B ju g stad (1966) used a te m p e ra tu re h u m id ity index (THI)
t o i n c o r p o r a t e b o th t e m p e r a t u r e and h u m i d i t y and fo u n d a h i g h l y
s i g n i f i c a n t m u l t i p l e c o r r e l a t i o n o f .968 b e tw e e n THI and tim e s p e n t
g ra z in g .
G r a z in g t i m e a l s o i n c r e a s e d when w ind s p e e d i n c r e a s e d on
h o t, humid days.
In an ex p erim en t conducted i n Colorado from A p ril t o
O c to b e r , R i t t e n h o u s e and S e n f t (1982) fo u n d t h a t g r a z i n g t i m e was
m a x im a l when d a i l y t e m p e r a t u r e
te m p e ra tu re (a 12-day
c o in c id e d
w ith
running te m p e r a tu r e mean).
an a c c lim a te d
Any d e v ia t io n from
th e a c c lim a te d te m p e ra tu re reg im e r e s u l t e d i n a d e c re a s e in g ra z in g
9
tim e .
A low t o i n te r m e d ia te , i n c r e a s e i n b a ro m e tric p r e s s u r e r e s u l t e d
i n a r a p i d i n c r e a s e i n g r a z i n g t i m e ; h o w e v e r, when h i g h p r e s s u r e
changes w ere observed g ra z in g tim e d e c re a se d g r a d u a lly .
Dwyer (1961)
found a d e c r e a s e i n g r a z in g tim e w ith in c r e a s i n g te m p e r a tu r e .
Three
d i f f e r e n t t e m p e r a t u r e l e v e l s w e r e s t u d i e d : b e lo w 27 C, 2 7 -2 9 C and
a b o v e 29 C. The g r a z i n g m e a n s w e r e 8 . 7 0 ,
re sp ec tiv e ly .
7*98 a n d 6 .6 5 h r / d ,
Adverse w i n t e r w e ath e r may a ls o d e c r e a s e g ra z in g tim e .
Adams e t a l . (1986) d i s c o v e r e d t h a t when minimum d a i l y t e m p e r a t u r e
(MDT) r a n g e d fro m 0 t o - 3 5 C t h e s i m p l e c o r r e l a t i o n b e tw e e n MDT and
d a i l y g r a z in g tim e was .60 (P<.01).
C a t t l e p r e f e r to g ra z e i n d a y l i g h t and i t i s o n ly when t h e h o u rs
o f l i g h t become s h o r t o r when d a y t i m e t e m p e r a t u r e s a r e t o o h i g h f o r
c o m fo rt t h a t c a t t l e spend an a p p r e c ia b le p a r t o f t h e i r g r a z in g tim e i n
d a r k n e s s (H a n co c k ,
1953)«
Hancock (1953) a l s o f o u n d a p o s i t i v e
r e l a t i o n s h i p w ith le n g th o f day and d a y l i g h t g ra z in g tim e .
and Bueno (1978) f o u n d s i m i l a r r e s u l t s .
Ruckebusch
They r e p o r t e d t h a t ti m e o f
o n s e t and r e s e t o f g ra z in g was c o r r e l a t e d (.89) t o t h e c o rresp o n d in g
tim e s o f s u n r i s e and s u n s e t.
The e n v i r o n m e n t a l s o e f f e c t s t h e d i s t a n c e a g r a z i n g a n i m a l
t r a v e l s and su b seq u en t use of th e ra n g e lan d .
Rain and wind i n t e r a c t
w ith c a t t l e a c t i v i t i e s t o d e c re a se t h e tim e sp en t w a lk in g (Ruckebusch
and B u en o , I 9 78).
A n d e rso n a n d Kothmann (1980) fo u n d t h a t 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 g r a z in g sy ste m , as te m p e r a t u r e d e crea se d
w i t h i n t h e r a n g e o f 35 t o - 3 C s u b s e q u e n t t r a v e l d e c r e a s e d . On s e m i a r i d and a r i d ra n g e la n d s t h e l o c a t i o n o f w a te r had a dominant e f f e c t
on use o f v e g e ta tio n .
On th e s e ra n g e la n d s w a te r was o f t e n r e s t r i c t e d
10
t o one o r tw o l o c a t i o n s and d e g r e e o f u s e o f v e g e t a t i o n d e c r e a s e d
l i n e a r l y or e x p o n e n ti a lly from a w a te r so u rce (Arnold and D udzinski,
1 9 7 8 ).
M u e g g le r (1965) r e p o r t e d
t h a t p e r c e n t s l o p e and d i s t a n c e
upslope acco u n ted f o r 81$ o f th e v a r i a t i o n i n r e l a t i v e g ra z in g use on
mountainous l i v e s t o c k range i n so u th w e ste rn Montana.
11
MATERIALS AND METHODS
The s t u d y was c o n d u c te d d u r i n g t h e sum m ers o f 19 85 and 1986 on
m ountain f o o t h i l l ran g elan d i n th e Bear Paw M ountains, 32 km s o u th e a s t
o f H a v re, M ontana, i n c o o p e r a t i o n w i t h t h e N o r t h e r n A g r i c u l t u r a l
R esearch C en ter.
The s t u d y s i t e had an a v e r a g e e l e v a t i o n o f I ,300 m
w i t h s l o p e s r a n g i n g fr o m
5 t o 40%. Long te r m a n n u a l p r e c i p i t a t i o n
ranged from 45.7 t o 50.8 cm.
The m ajor g r a s s e s on th e stu d y s i t e were
ro u g h f e s c u e ( F e s t u c a s c a b r e l l a ) , I d a h o f e s c u e (F e s t u c a i d a h o e n s i s )
and bluebunch w h e a tg ra s s (Agropyron s p ic a tu m ) on th e upland a r e a s and
Kentucky b lu e g r a s s (Poa p r a t e n s i s ) on th e low land a re a s .
In
1985,
24 cow s o f f o u r b r e e d t y p e s w e re u s e d ;
6 e ac h o f
s t r a i g h t H ereford (HH), 50% Angus - 50% H ereford (AH) , 50% Simmental 50% H ereford (1S1H) and 75% Simmental - 25% Hereford (3S1H).
The cows
r a n g e d ! n ag efro m 6 t o 9—y r —o ld and w e re s e l e c t e d a t random ( w i t h i n
b r e e d t y p e ) from t h e cow h e r d .
A ll cow s w e re l a c t a t i n g and fro m a
common m anagem ent b a c k g r o u n d .
A ll c a l v e s w e re s i r e d by H e r e f o r d
b u lls.
The p a s tu r e used i n 1985 was a p p ro x im a te ly 320 ha i n s i z e and
c o n t a i n e d 250 l a c t a t i n g cow s fro m J u l y 22 t o S e p te m b e r 16 f o r a
s t o c k i n g r a t e o f .67 ha/AUM.
th e p a s tu r e (F ig u re I).
W a te r w as a v a i l a b l e a t t h r e e a r e a s i n
The d i s t a n c e b e tw e e n t h e r e s e r v o i r and t h e
creek was a p p ro x im a te ly 1.6 km.
The 24 cows w e re e q u ip p e d w i t h v i b r a c o r d e r s , a s d e s c r i b e d by
Stobbs (1970), t o e s t i m a t e g ra z in g tim e .
a n im a ls from J u ly 23 t o September 16.
V ib ra c o rd e rs rem ained on th e
C harts were changed and c lo c k s
w e re rew ound a t a p p r o x i m a t e l y 9 -d i n t e r v a l s .
w a te rin g
areas
w e re
used
to
m in im ize
P o rta b le c o rra ls
a n im al
d istu rb a n c e
at
when
12
Creek
( ^ ) R e s e rv o ir
Developed Spring
Figure I. Map of pasture during 1985, I" = 442m..
13
v i b r a c o r d e r s w e re c h a n g e d .
g ra z in g tim e s were d is re g a r d e d .
On d a y s when e q u ip m e n t was c h a n g e d ,
Each day's g r a z in g tim e was d iv id e d
i n t o e i g h t 3 - h r p e rio d s (2400-0300, 0300-0600, 0600-0900, 0900-1200,
1200-1500, 1500-1800, 1800-2100 and 2100-2400).
Grazing tim e was a l s o
d i v i d e d i n t o two l e v e l s o f g r a z i n g w i t h i n e a c h p e r i o d .
L e v e l one
g r a z i n g was d e f i n e d a s any s o l i d m a rk s o f 15 min o r g r e a t e r .
Level
two g ra z in g was d e fin e d by i n t e r m i t t e n t marks w ith sp a c e s l e s s th a n 15
min a p a r t .
D istan c e
tra v e le d
w as e s t i m a t e d
(A n d e rso n and K othm ann, 1977).
tim e
v ib ra c o rd e rs
w e re
by t h e
use
of p ed o m eters
P e d o m e te r s w e re r e a d a n d r e s e t e a c h
changed.
C a lib ra tio n
fa c to rs
w e re n o t
c a l c u l a t e d i n 1985 b u t i n 1986 th e cows w ere walked a known d i s t a n c e
fro m one c o r r a l t o a n o t h e r , t h e n r e a d i n g s w e re takerji and p e d o m e t e r s
re se t.
The c a t t l e w e re t h e n w a lk e d b a ck t o t h e o r i g i n a l c o r r a l and
■ '
re a d in g s w ere a g ain ta k e n . The c a l i b r a t i o n f a c t o r s f o r b o th d i s t a n c e s
.
were th e n averaged to compute a f i n a l c a l i b r a t i o n f a c t o r f o r each cow.
Since t h e same ty p e of pedom eter was used both y e a r s , t h e c a l i b r a t i o n
fa c to rs
fo r
1986 w e re
a v e r a g e d and u s e d
c a l i b r a t i o n f a c t o r used i n 1985 was .894.
in
1985.
The a v e r a g e
This f a c t o r was m u l t i p l i e d
by t h e a c t u a l p e d o m e t e r r e a d i n g s and t h e n d i v i d e d by t h e n u m ber o f
days t h e pedom eter was on t h e anim al t o e s t i m a t e d i s t a n c e i n km/d.
B i t e r a t e m e a s u r e m e n ts w e re t a k e n t h r o u g h o u t t h e e x p e r i m e n t .
B i t e r a t e ( b i t e s / m i n ) was c a l c u l a t e d by co u n tin g t h e number of b i t e s
i n a 5-m in tim e p e rio d .
s t o p w a t c h w as u s e d .
A w atch w ith ah ind ep en d en t 5-m in ti m e r and
The s t o p w a t c h w as s t o p p e d when an a n i m a l q u i t
b i t i n g and th e o b s e r v a tio n was concluded when th e 5-m in alarm sounded.
X
14
A hand h e ld c o u n te r was used t o count t h e number o f b i t e s .
The number
of b ite s
c a lc u la te
b ite s/m in .
w as t h e n
d iv id e d
by t h e
sto p w a tc h
tim e
to
A te le s c o p e was used t o w atch th e cows e a r l y i n t h e season
u n t i l they could be approached on ho rseb ack w ith o u t d is tu r b a n c e .
B ite
r a t e s w ere o n ly ta k e n from 0600-0900 and 1800-2100, th e s e tw o .p e r io d s
w e re i d e n t i f i e d
p e r io d s .
by ( L a t h r o p , 1985) a s t h e m a jo r d i u r n a l g r a z i n g
C om m ercially a v a i l a b l e s to c k dye was used t o number a l l cows
so a n im a ls could be i d e n t i f i e d from a d i s ta n c e .
Milk p r o d u c tio n , c a l f w e ig h ts and cow w e ig h ts w ere ta k e n tw ic e i n
1985 and t h r e e t i m e s i n 1986 d u r i n g t h e e x p e r i m e n t s . T e s t d a y s w e re
A u g u st 2 and 2 9 , I 985 and J u l y 18, A u g u st 22 and S e p te m b e r 3 0 , I 986.
Milk p ro d u c tio n was e s ti m 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 i l l i a m s e t a l . , I 9 79).
A 9 o r 10 h r c o w - c a l f s e p a r a t i o n i n t e r v a l
was used p r i o r t o m easuring m ilk p ro d u c tio n and cow and c a l f w e ig h ts.
Milk p ro d u c tio n was th e n c o n v erted t o a 2 4 -h r b a s i s .
I n 1 986, 24 l a c t a t i n g cows w e re a l s o u sed b u t t h r e e new b r e e d
groups w ere added t o t h e HH b reed group;
T a r e n ta is e - H ereford (TH),
T a r e n ta is q - Sim m ental ^ H ereford (T(SH)) and C h a r o la is - Sim mental H ereford (C(SH)).
The TH w ere s i x 50% T a r e n ta is e - 50% H ereford cows,
t h e T(SH) c o n s i s t e d o f t h r e e 50% T a r e h t a i s e - 25% S im m e n ta l - 25%
H ereford and t h r e e 50% T a r e n ta is e - 37.5% Simmental - 12.5% Hereford
cows and th e C(SH) group c o n tain ed f i v e 50% C h a ro la is - 25% Simmental
- 25% H e r e f o r d cow s and one 50% C h a r o l a i s - 37.5% S im m e n ta l - 12.5%
H ereford cow. Cows were a l l 3 - y r - o l d and th e c a lv e s w ere a l l s i r e d by
H ereford b u l l s .
The p a s t u r e i n I 986 was a p p r o x i m a t e l y 27.6 h a and
co n tain ed 56 cows from June I t o O ctober I f o r a s to c k in g r a t e o f 1.2
15
ha/AUM.
W ate r was a v a i l a b l e i n t h r e e l o c a t i o n s ( F i g u r e 2 ).
The
d is ta n c e betw een r e s e r v o i r I and th e s to c k ta n k was a p p ro x im a te ly 1.5
km.
I n a d d i t i o n t o g r a z i n g tim e * d i s t a n c e t r a v e l e d and b i t e r a t e ,
I
forage a v a i l a b i l i t y
w as m e a s u r e d
p e rio d ic a lly
e x p e r i m e n t fro m A u g u st 5 t o S e p te m b e r 12 i n 1986.
th ro u g h o u t
th e
At t h e t i m e b i t e
r a t e o b s e r v a t i o n s w e re t a k e n cow s w e re ra n d o m ly c h o s e n a n d f o r a g e
a v a i l a b i l i t y was e s t i m a t e d i n . t h e a r e a where b i t e r a t e was observed.
A v a i l a b i l i t y w as e s t i m a t e d by c l i p p i n g f o u r .18 m e t e r r i n g s th r o w n
from th e c e n t e r o f t h e g ra z in g a r e a .
g ro u n d and g r a s s e s ,
sep a ra te ly .
Forage was c lip p e d 2 cm from t h e
f o r b s and s h r u b s w e re s e p a r a t e d and b a g g ed
The sam ples w ere th e n d r ie d i n a 500 w a tt microwave oven.
Forage a v a i l a b i l i t y was th en c o n v erted t o a k g /h a b a s i s .
D a ta w e re a n a l y z e d by l e a s t - s q u a r e s a n a l y s i s o f v a ria n c e u sin g
GLM p r o c e d u r e s o f S t a t i s t i c a l
A n a ly sis
S y ste m s
(SAS)
(1 9 8 5 ).
D i f f e r e n c e s b e tw e e n m eans w e re t e s t e d u s i n g t h e l e a s t s i g n i f i c a n t
d i f f e r e n c e method (SAS, 1985).
A m ix e d m o d el was u s e d f o r a n a l y s i s o f g r a z i n g t i m e , d i s t a n c e
t r a v e l e d and b i t e r a t e .
The l i n e a r m athem atical model was a s f o llo w s :
Yi j k = u + Bi + I j + BIi j + C(BIi j )k + e i j k i
where
Yi j k i = an o b s e r v a tio n (g ra z in g tim e ,
d is ta n c e t r a v e l e d o r b i t e
r a te ),
u = t h e o v e r a l l mean,
Bi = t h e f ix e d e f f e c t o f th e i t h b re e d ty p e ,
I . =
th e f ix e d e f f e c t o f th e j t h sex o f c a l f ,
16
R e s e rv o ir I
R e s e rv o ir 2.
.W • E
Stoqk Tank
Figure 2. Map o f pasture during 1986, I" = 348m.
17
B Ii J = t h e i n t e r a c t i o n b e tw e e n t h e i t h b r e e d t y p e and t h e J t h
c a l f sex ,
C(BIi J ) k = t h e random e f f e c t p f t h e k t h cow w i t h i n t h e i J t h BI
in te ra c tio n ,
Bi J k l = randpm e r r p r .
The random e f f e c t o f C(BIi J)k was used a s t h e e r r o r term to t e s t
th e f ix e d e f f e c t s ,
c a l f sex and b reed x c a l f sex i n t e r a c t i o n because
o f r e p e a t e d m e a s u r e m e n t s t a k e n on e a c h a n im a l ( G i l l and H a fs 1 9 7 1 ).
Grazing tim e was a ls o t e s t e d by i n t e n s i t y o f g ra z in g .
The l i n e a r and q u a d r a t i c e f f e c t o f day wps a d d e d t o t h e ab o v e
mao d e l and t e s t e d w i t h t h e
ty p e s o f p h ser v a tio p s .
r e s i d u a l a s th e e r r o r te rm in a l l th r e e
I n t h e b i t e r a t e a n a l y s i s t i m e o f day (am o r
pm) o f t h e o b s e r v a t i o n , o b s e r v e r , o b s e r v e r by b r e e d i n t e r a c t i o n and
b r e e d by 4%y i n t e r a c t i o n w e re a d d ed t o t h e m o d el a s i n d e p e n d e n t
v a ria b les.
The t h r e e o b s e r v a tio n s (g ra z in g ti m e , d is ta n c e t r a v e l e d and b i t e
ra te )
w e re a v e r a g e d t o
d e term in e
if
th e p ro d u c tio n
c o v a ria te s
(average cow w e ig h t, average w e ig h t:h e ig h t r a t i o , av erage c a l f w e ig h t,
av erage m ilk p ro d u c tio n , cow c o n d itio n s c o r e , c a l f c o n d itio n s c o re and
c a l f age) had any e f f e c t on t h e dependent v a r i a b l e s .
P ro d u ctio n c h a r a c t e r i s t i c s (cow w e ig h t, m ilk p ro d u c tio n and c a l f
w eig h t) were a ls o a n aly zed .
They w ere analyzed a s dependent v a r i a b l e s
and t e s t e d u s in g th e f i r s t model d e s c r ib e d w ith t e s t day and b reed x
t e s t day i n t e r a c t i o n added.
18
RESULTS AND DISCUSSION
1985 P ro d u ctio n C h a r a c t e r i s t i c s
The p rim ary reaso n f o r m easuring p ro d u c tio n c h a r a c t e r i s t i c s was
t o v e r i f y t h a t t h e d i f f e r e n t b r e e d t y p e s u s e d i n t h e s tu d y h a v e
d i f f e r e n t p ro d u c tio n p o t e n t i a l as r e p o r te d by p re v io u s r e s e a r c h a t th e
same l o c a t i o n (C a s e b o lt, 1984; L a th ro p , 1985).
a n a l y s e s o f v a r i a n c e f o r cow body w e i g h t ,
p ro d u c tio n a re p re se n te d
i n T a b le I .
The l e a s t - s q u a r e s
c a l f w e i g h t and m i l k
The b r e e d t y p e m eans and
s ta n d a rd e r r o r s f o r th e s e t r a i t s a r e l i s t e d i n Table 2.
The b reed x t e s t day i n t e r a c t i o n was found to be n o n s i g n i f i c a n t
(P>.10) f o r cow w e i g h t and m i l k p r o d u c t i o n .
The i n t e r a c t i o n was
s i g n i f i c a n t (PC.10) f o r c a l f w e i g h t b u t t h e i n t e r a c t i o n was due t o a
c h an g e i n m a g n itu d e r a t h e r t h a n a c h an g e i n rank.
C a l f s e x and b r e e d x c a l f s e x i n t e r a c t i o n w e re n o t s i g n i f i c a n t
f o r any o f th e p ro d u c tio n m easurements.
The l e a s t - s q u a r e s means f o r
m ilk p r o d u c t i o n , cow body w e i g h t and c a l f w e i g h t w e re 10.6 + .8 and
9.6 + . 8 , 589 + 1 8 and 605 ± 18 and 183 ± 7 and 172 ± 7 kg f o r s t e e r
and h e i f e r c a lv e s , r e s p e c t i v e l y .
Cow body w eight was 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 among t h e f o u r
b reed ty p e s .
The r a n k i n g o f t h e b r e e d
r e p o r t e d by L a t h r o p (1 9 8 5 ).
ty p e s a g re e s w ith
th a t
L a t h r o p fo u n d t h a t t h e HH cows w e re
l i g h t e r (PC.01) th a n th e Simmental c r o s s cows.
The Sim m ental c r o s s cows had h e a v ie r c a lv e s th a n t h e HH cows bu t
th e ISIH cows d id no t d i f f e r from th e AH cows in c a l f w e ig h t.
and AH d i d n o t d i f f e r i n c a l f w e i g h t .
The HH
T hese r a n k i n g s a l s o t e n d t o
fo llo w th e r e s u l t s found by LathrOp (1985).
19
Table I . L e a s t- s q u a r e s a n a ly s e s o f v a ria n c e f o r cow body w eight (BW),
c a l f w eight (CW) and m ilk p ro d u c tio n (MP) (1985)
Mean s q u a re s
BW
(k g )2
CW
( k g /d ) 2
MP
(k g )2
3
6062.2
2 0 8 0 .O+
31.7*
C a lf sex .
I
2183.6
U l 8 .7
13-1
T est day
I
1351.5*
10299-0*
.02
Cow(breed x c a l f sex) 19
5088.6*
778.5*
10.1*
)
Source
df
Breed type
Breed x t e s t day
R esidual
3
90.0
2 4 . B+
7 .9
20
55.6
8.6
4.3
.81
•99
.99
R2
+ P< .10
* PC.05
Table 2 . L e a s t- s q u a r e s means and s ta n d a r d e r r o r s f o r body w eight (BW),
c a l f w eight (CW) and m ilk p ro d u c tio n (MP) (1985)
CW
(kg)
MP
(k g /d )
Breed t y p e a
N
BW
(kg)
HH
6
570 ± 28b
166 ± 7°
7.6 + I ^ c
AH
6
586 ± 22b
171 ± 7cd
9 - 6 + 1 .Ocd
ISIK
6
608 + 22b
184 + 7de
11 .8 + I .Od
3S1H
6
623 ± 28b
197 ± 7e
11.4 + 1 .2 d
a H = H erefo rd , A = Angus, S = S im m en ta l.
^Body w eight ( P X I O ) .
cdeMeans i n columns w ith d i f f e r e n t s u p e r s c r i p t s d i f f e r (PC.IO).
Milk p ro d u c tio n f o r th e Sim mental c r o s s was s i g n i f i c a n t l y h ig h e r
t h a n m i l k p r o d u c t i o n f o r t h e HH cows b u t n o t d i f f e r e n t fro m t h e AH
cows. C ase b o lt (1984) found t h a t th e ISIH and AH cows had h ig h e r m ilk
p r o d u c t i o n t h a n t h e 3 S I H cows (P <.05).
lo w e s t m ilk p ro d u c tio n .
The HH cow s a l s o showed t h e
Lathrop (1985) found t h a t i n t h e e a r l y s ta g e s
o f l a c t a t i o n th e Sim mental c r o s s cows were h ig h e r i n m ilk p ro d u c tio n
t h a n t h e HH o r AH cow s.
I n t h e s t u d y by C a s e b o l t (1984) many more
o b s e r v a tio n s were ta k en on m ilk p ro d u c tio n so th e d i f f e r e n c e s between
s t u d i e s may be due t o sample s iz e .
Time Spent Grazing
The l e a s t - s q u a r e s a n a l y s i s o f v a r i a n c e f o r t o t a l d a i l y g r a z i n g
h o u r s i s p r e s e n t e d i n T a b le 3 .
The o v e r a l l d a i l y g r a z i n g mean was
11.9 h r / d w ith a s ta n d a rd d e v ia t io n o f 1.1 h r / d (649 o b s e r v a tio n s w ith
an average o f 27 d a i l y g ra z in g o b s e r v a tio n s p e r cow).
T his i s h ig h e r
t h a n t h e o v e r a l l g r a z i n g mean o f 9.4 h r / d r e p o r t e d by L a th r o p (1985)
u s in g t h e same f o u r b reed ty p e s.
The d i f f e r e n c e s a r e probably due to
e n v iro n m en t, m ainly fo ra g e a v a i l a b i l i t y .
T o t a l d a i l y g r a z i n g h o u r s w e re 11.8 + .2 , 12.3 + .2 , 11.6 + .2
and 11.6 + .5 h r / d f o r HH1 AH, ISIH and 3S1H c o w s,
There was a tendency f o r
re sp e c tiv e ly .
AH cows t o g ra z e lo n g e r th a n t h e HH and ISIH
cows (P= .1 0) b u t t h e y d i d n o t d i f f e r fro m t h e 3S1H cow s (P>.1 0). When
l o o k i n g a t t h e b r e e d t y p e m ean s, t h e s e d i f f e r e n c e s a p p e a r s m a l l and
may n o t
be
b io lo g ic a lly
sig n ific a n t.
L a th r o p
(1985)
fo u n 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 t o t a l d a i l y g r a z i n g t i m e u s i n g t h e same
f o u r breed ty p e s a t th e same l o c a t i o n .
21
Table 3«
L e a s t- s q u a r e s a n a l y s i s o f v a ria n c e f o r t o t a l d a i l y g ra z in g
time (1985)
Mean s q u a re s
(h r/d )*
df
Source
15.34
Breed type
3
Cow(breed)
18
6.35*
L in e a r
I
Q uadratic
I
66.61**
teir
57.53
R egression o f day
R esidual
1.53
625
.37
R2
* P< .05
B re ed t y p e s w e re a l s o t e s t e d f o r d i f f e r e n c e s among l e v e l s o f
g r a z i n g i n t e n s i t y b u t t h e r e was no s i g n i f i c a n t e f f e c t (P>.10).
No
p r o d u c t i o n c o v a r i a t e s o r c a l f s e x w e re s i g n i f i c a n t i n e x p l a i n i n g
v a r i a t i o n i n g ra z in g tim e .
L athrop (1985) found t h a t c a l f age and cow
m ilk p r o d u c tio n had an e f f e c t on g r a z in g tim e . Other r e s e a r c h e r s have
found no e f f e c t o f m ilk p ro d u c tio n on g ra z in g tim e (Jo h n sto n e-W a lla ce
and Kennedy,
1944; Hancock 1950; J o h n sto n e -W a lla c e ,
1951).
C a lf age
i s an i n d i c a t i o n o f s t a g e o f l a c t a t i o n o f t h e cow w i t h o l d e r c a l v e s
b eing i n l a t e r s t a g e s o f l a c t a t i o n when m ilk p r o d u c tio n i s lo w e r.
c a lv e s were o v e r 60 d old when m ilk p ro d u c tio n
A ll
was measured. C asebolt
(1984) show ed t h a t m i l k p r o d u c t i o n d e c r e a s e d l i n e a r l y a f t e r 60 d o f
22
a g e , m i l k p r o d u c t i o n and c a l f age. s h o u ld be n e g a t i v e l y c o r r e l a t e d .
C o n f lic tin g r e s e a r c h r e s u l t s a d d re s s in g th e e f f e c t o f m ilk p ro d u c tio n
on
g ra z in g
tim e
in d ic a te s
th a t
th is
re la tio n sh ip
is
not
w e ll
u n d e rsto o d .
F ig u r e 3 i l l u s t r a t e s th e e f f e c t o f day o f th e y e a r on t o t a l d a i l y
g r a z i n g t i m e . As s e a s o n p r o g r e s s e d fro m day 200 t o d a y 260 g r a z i n g
tim e in c r e a s e d t o a maximum o f a p p ro x im a te ly 12.5 h r and th e n le v e l e d
o ff.
T h i s y e a r a v e r a g e p r e c i p i t a t i o n was 12.4 cm co m p ared t o an
a v e r a g e p r e c i p i t a t i o n o f 46 - 51 cm, so we assu m e d e c l i n i n g f o r a g e
a v a i l a b i l i t y w ith tim e .
R e s e a r c h h a s shown t h a t u n d e r d e c l i n i n g
fo ra g e a v a i l a b i l i t y g ra z in g tim e i n c r e a s e s (A llden,
1970;
Chacon and
S t o b b s , 1976; J a m i e s o n and H odgson, 1979; Zoby and H o lm e s, 1983;
S c a r n e c c h i a e t a l . , 1 985).
Stobbs (1975) e s ti m a te d t h a t g ra z in g tim e i s l i m i t e d by f a t i g u e .
F a tig u e l i m i t s were e s ti m a te d a t a p p ro x im a te ly 12 h r / d g ra z in g .
i s supported, by t h e maximum g r a z in g tim e i n
T his
F ig u re 3-
Time o f Day Grazing
The l e a s t - s q u a r e s
g ra z in g i s
a n a l y s i s o f v a r i a n c e f o r t h e t i m e o f day
p re s e n te d i n Table 4.
tim e o f day g ra z in g .
Breed ty p e was n o t s i g n i f i c a n t f o r
Each p e rio d was a l s o analyzed f o r breed e f f e c t
and no b r e e d e f f e c t w as fo u n d f o r a n y p e r i o d .
o v e r a l l t i m e o f day g r a z i n g m e an s.
F i g u r e 4 show s t h e
The m a jo r p e r i o d s o f g r a z i n g
o c cu rred from 600-900 h r and 1800-2100 h r.
These tim e p e rio d s were
a l s o i d e n t i f i e d as t h e m ajor g r a z in g p e rio d s by L athrop (1985) u s in g
t h e same b r e e d t y p e s .
O th e r r e s e a r c h e r s h a v e fo u n d s i m i l a r g r a z i n g
p a t t e r n s f o r c a t t l e on summer p a s t u r e (Dwyer, 1961; Kropp e t a l . ,
23
14-i
Y = -6 9 .8 3 + .66X - .0013X*
13-
12A
A
11-
10-
9-
8 -------
200
_ r_
210
— I--------------- 1----------1
— i----------- 1
220
250
230
240
JUUAN DAY
Figure 3. Effect of day of the year on total daily grazing time
during 1985. Triangles indicate daily grazing means.
260
24
1973;
Arnold and D u d z in sk l, 1978; Zoby and Holmes, 1983).
Table 4 .
L e a s t- s q u a r e s a n a l y s i s o f v a ria n c e f o r tim e o f day g ra z in g
(1985)
Mean s q u a re s
df
(h r)2
Breed ty p e
3
I .6
Grazing tim e p e rio d
7
312.7*
18
1 .0*
Source
Cow(breed)
R esidual
.5
5163
.46
R2
b P.< .05
B i t e Rate
The l e a s t - s q u a r e s a n a l y s i s o f v a r ia n c e f o r b i t e r a t e i s p re s e n te d
i n T a b le 5.
cow.
An a v e r a g e o f 8 b i t e r a t e o b s e r v a t i o n s w e re t a k e n p e r
Breed was a s i g n i f i c a n t so u rce o f v a r i a t i o n f o r b i t e r a t e .
The
l e a s t - s q u a r e s m eans f o r b i t e r a t e w e re 52.7 + 1 .5 , 56.2 + 1.5» 53-2 +
1.4 and 59.0 + 1.6 f o r BH, AH, ISIH and 3S1H, r e s p e c t i v e l y .
The 3 SI H
had a h ig h e r b i t e r a t e (P<.05) th a n th e HH and ISIH bu t d id n o t d i f f e r
fro m t h e
AH (P>.10).
The AH had a h i g h e r b i t e r a t e (PC.05) t h a n t h e
I SI H and t h e HH b u t t h e ISIH and HH d i d n o t d i f f e r (P>.1 0 ).
Time o f day i n w h ic h t h e b i t e r a t e m e a s u r e m e n ts w e re t a k e n w as
a l s o a s i g n i f i c a n t fo rm o f v a r i a t i o n .
The b i t e r a t e m e a s u r e m e n ts
ta k e n from 1800-2100 h r w ere h ig h e r th an th e b i t e r a t e measurements
ta k e n
from
600-900
h r,
5 6 .3
±
.7
and
5 4 .3
± -7 b i t e s / m i n ,
GRAZING TIME (hr)
TIME OF DAY (x 1 0 0 )
Figure 4. Time of day grazing during 1985.
letters differ (P<.05).
Bars with different
26
re sp e c tiv e ly .
O bserver a l s o d i f f e r e d i n b i t e r a t e o b s e r v a tio n s but th e o b s e rv e r
x b r e e d i n t e r a c t i o n Was n o t s i g n i f i c a n t . O b s e r v e r 2 r e p o r t e d h i g h e r
b i t e r a t e s th a n d id o b s e r v e r I ,
59-3 ± »7 and 51.3 ±.9 b i t e s / m i n ,
re sp e c tiv e ly .
Breed x l i n e a r r e g r e s s i o n on day i n t e r a c t i o n was t e s t e d and found
to be n o n s i g n i f i c a n t (P>.10) so r e g r e s s i o n s were pooled a c r o s s b reed
ty p e s
and F i g u r e 5 show s t h e e f f e c t o f day on b i t e r a t e .
As s e a s o n
p r o g r e s s e d fro m day 210 t o d ay 260 b i t e r a t e i n c r e a s e d l i n e a r l y .
O ther r e s e a r c h e r s have shown t h a t a s fo ra g e a v a i l a b i l i t y d e c li n e s b i t e
r a t e i n c r e a s e s (Chacon and S to b b s,
Zoby
and
H o lm e s,
1983;
1976; Jam ieson and Hodgson,
S c a rn e c c h ia
et
a l.,
1 9 8 5 ).
1979;
T herefore,
d e c l i n i n g fo r a g e a v a i l a b i l i t y could have caused th e observed i n c r e a s e
in b ite ra te .
None o f t h e p r o d u c t i o n c o v a r i a t e s o r c a l f s e x w e re
s i g n i f i c a n t i n th e b i t e r a t e a n a l y s i s .
D is ta n c e tr a v e l e d
The l e a s t - s q u a r e s a n a l y s i s o f v a r ia n c e f o r d i s t a n c e t r a v e l e d i s
p re s e n te d i n T ab le 6. An average o f 6 pedom eter re a d in g s p e r cow were
t a k e n i n 1985.
B re e d t y p e was s i g n i f i c a n t i n t h i s a n a l y s i s and t h e
b r e e d m eans f o r d i s t a n c e t r a v e l e d w e re 3«1 ± *2, 3.4 + .2 , 4.0 +.2 and
2.8 + .2 km /d f o r HH, AH, ISIH and 3S1H c o w s, r e s p e c t i v e l y .
The ISIH
cows t r a v e l e d s i g n i f i c a n t l y f a r t h e r (PCIO) th a n t h e o th e r t h r e e b reed
ty p e s.
t h e HH.
The AH t r a v e l e d f a r t h e r th a n th e 3S1H but d i d n o t d i f f e r from
T h i s r e l a t i o n s h i p i s o p p o s i t e o f w h a t L a t h r o p (1985) fo u n d
where ISIH cows t r a v e l e d l e s s th a n th e o t h e r th r e e b reed ty p e s th e s e
d i f f e r e n c e s were pro b ab ly due t o th e d i f f e r e n c e s i n y e a r s .
The b reed
27
Table 5.
L e a s t- s q u a r e s a n a l y s i s o f v a ria n c e f o r b i t e r a t e (1985)
Mean s q u a re s
Source
df
( b it e s /m in ) ^
Breed type
3
347.4*
Cow(breed)
20
89.2*
Time o f day
I
1 4 3 .I +
O bserver
I
1878.1*
L in e a r r e g r e s s i o n on day I
4424.1*
R esidual
160
43.0
R2
+
.68
P<.10
P< .05
t y p e m eans w e re 5.0 ± .2 , 4.8 + .2 , 4.1 + .2 and 4.8 + .2 km /d f o r HH,
AH1 ISIH and 3S1H,
re sp ec tiv e ly .
None o f th e p ro d u c tio n c o v a r i a t e s ,
c a l f s e x , o r l i n e a r o r q u a d r a t i c r e g r e s s i o n s on day w e re s i g n i f i c a n t
(P>.10) i n th e d i s t a n c e t r a v e l e d a n a l y s i s .
1986 P ro d u ctio n C h a r a c t e r i s t i c s
L im ite d
d a ta have
b e en c o l l e c t e d
c o m p a r in g
c h a r a c t e r i s t i c s o f th e f o u r b reed ty p e s used i n 1986.
th e
p ro d u c tio n
The T a r e n ta is e
and C h a r o l a i s b r e e d s a r e r e l a t i v e l y new b r e e d s t o t h i s r e s e a r c h on
m a te rn a l t r a i t s a t th e N orthern A g r i c u l t u r a l Research C enter a t Havre,
M ontana.
b reed
The T a r e n t a i s e b r e e d w as c h o s e n b e c a u s e i t i s a s m a l l e r
th a n
Consequently
S im m e n ta l
w ith
re la tiv e ly
h ig h
m ilk p ro d u c tio n .
th e T a r e n ta is e b reed may r e q u i r e l e s s energy in ta k e and
s t i l l have s u f f i c i e n t m ilk p ro d u c tio n .
28
Y = -31.75 + 0.37X
r* = .68 (p<.01)
3
230
2
JULIAN DAY
Figure 5. Effect of day of the year on bite rate during 1985.
Triangles indicate daily bite rate means.
)
29
Table 6 .
L e a s t- s q u a r e s a n a l y s i s o f v a r ia n c e f o r d i s t a n c e t r a v e l e d
(1985)
Mean s q u a re s
Source
df
(km/d)2
Breed
3
4 . Ob
20
.6
Cow(breed)
.5
m
R esid u a l
.31
R2
* P< .05
The l e a s t - s q u a r e s a n a ly s e s o f v a ria n c e f o r cow body w eig h t, c a l f
w e i g h t and m i l k p r o d u c t i o n f o r t h e a n i m a l s u s e d i n t h e s tu d y a r e
p re s e n te d i n Table 7 and th e l e a s t - s q u a r e s means and s ta n d a r d e r r o r s
a r e p r e s e n t e d i n T a b le 8.
The b r e e d x t e s t day i n t e r a c t i o n was n o t
s i g n i f i c a n t (P>.10) f o r cow body w eig h t and m ilk p ro d u c tio n , but was
s i g n i f i c a n t (P<.10) f o r c a l f w e i g h t .
t e s t days th a n any o f th e o th e r b re e d s.
The HH b r e e d w as l o w e r on a l l
The HH b re e d was removed from
th e a n a ly s e s and th e i n t e r a c t i o n was n o t s i g n i f i c a n t .
The i n t e r a c t i o n
was due t o t h e HH b r e e d r e s p o n d i n g d i f f e r e n t l y t h a n t h e o t h e r t h r e e
b r e e d t y p e s on t h e t e s t d a y s .
C a l f s e x and b r e e d x c a l f s e x i n t e r a c t i o n w e r e n o t s i g n i f i c a n t
(P>.10)
fo r
any
of
th e
p ro d u c tio n
c h a ra c te ristic s
p ro d u c tio n where c a l f sex was s i g n i f i c a n t .
except
m ilk
The h e i f e r c a lv e s had dams
w ith h ig h e r m ilk p ro d u c tio n th a n th e s t e e r c a lv e s (PC.05).
The l e a s t -
s q u a r e s m eans f o r m i l k p r o d u c t i o n , cow body w e i g h t and c a l f w e i g h t
30
w e re 6 .8 + .3 and 8.6 + .3» 534.2 + 11.5 and 549*7 + 10.5 and 173*5 +
5.9 and 171*7 + 6.5 k g f o r s t e e r a n d h e i f e r c a l v e s ,
re sp e c tiv e ly .
C a s e b o l t (1984) a l s o r e p o r t e d t h a t t h e dams o f h e i f e r c a l v e s h ad
h ig h e r m ilk p ro d u c tio n th an dams o f s t e e r c a lv e s .
th a t
th e re
f i n d i n g , and
was r e s e a r c h
He a l s o i n d i c a t e d
b o t h s u p p o r t i n g and c o n t r a d i c t i n g t h i s
i t a p p e a rs t h a t th e r e l a t i o n s h i p i s n o t w e ll und ersto o d .
Table 7. L e a s t- s q u a r e s a n a ly s e s o f v a ria n c e f o r cow body w eight (BW),
c a l f w eight (CW) and m ilk p ro d u c tio n (MP) (1986)
Mean s q u a re s
CW
( k g /d ) 2
s > 3
(XI
BW
(k g) 2
Source
df
Breed ty p e
3
10910.3+
4582.7+
1 8 .2 *
C a lf sex
I
4086.5
134.8
49*5*
T est day
2
8 5 9 4 .16
25722.9*
Cow(breed x c a l f sex) 19
4004.3*
1 2 6 3 .6 *
Breed x t e s t day
R esidual
R=
+ P<.10
* P< .05
6
176.4
40
92*8
*97
1 1 . 6*
3*8
97*9+
4.3
17.0
2 .9
*99
.64
31
Table 8. L e a s t- s q u a r e s means and s ta n d a r d e r r o r s f o r body w eight (BW),
c a l f w eight (CW) and m ilk p ro d u c tio n (MP) (1986)
MP
(kg/d)
CW
(kg)
HH
6
535 ± I6b
154 + 7b
6.4 + .5b
TH
6
532 + 15b
168 ± 7bc
8 .5 ± .5°
T(SH)
6
530 + I6 b
185 ± 7C
C(SH)
6
572 + 16°
179 ± 7C
7 .5 ± .5bc
1+
Cn
O
N
Ul
Breed t y p e a
Co
BW
(kg)
8H = H e r e f o r d , T = T a r e n t a i se, C = C h a r o l a i s .
b c Means i n columns w ith d i f f e r e n t s u p e r s c r i p t s d i f f e r (P<.10).
The C(SH) cow s h ad s i g n i f i c a n t l y h e a v i e r body w e i g h t s t h a n t h e
o th e r th r e e breed ty p e s.
The HH cow s had c a l v e s t h a t w e re l i g h t e r
t h a n t h e T(SH) and C(SH) b r e e d t y p e s b u t w e re n o t d i f f e r e n t fro m t h e
TH.
This i s p ro b a b ly due t o in c r e a s e d h e t e r o s i s and in c r e a s e d grow th
fro m t h e S im m e n ta l b r e e d i n f l u e n c e .
The TH and t h e T(SH) cows h ad
h i g h e r m i l k p r o d u c t i o n t h a n t h e HH cow s (P<.05) b u t d i d n o t d i f f e r
from th e C(SH) cows.
m ilk p ro d u c tio n
Thus th e T a r e n t a i s e in f l u e n c e was t o
in c r e a s e
i n th e cows when compared t o H erefo rd and p o s s ib ly
C h a ro la is which ranked lo w e r though n o t s i g n i f i c a n t l y .
Time Spent Grazing
The l e a s t - s q u a r e s a n a l y s i s o f v a r i a n c e f o r t o t a l d a i l y g r a z i n g
h o u r s i s p r e s e n t e d i n T a b le 9*
The o v e r a l l d a i l y g r a z i n g mean w as
11.3 h r / d w ith a s ta n d a rd d e v ia t io n o f 1.0 h r /d (606 o b s e r v a tio n s w ith
an a v e r a g e o f 25 d a i l y g r a z i n g m e a s u r e m e n ts p e r cow ).
T h is was
s l i g h t l y lo w e r th a n th e p re v io u s y e a r (11.9 h r/d ) and i s probably due
t o b e t t e r e n v iro n m e n t, p r i m a r i l y fo ra g e a v a i l a b i l i t y .
32
Breed ty p e s d id n o t d i f f e r s i g n i f i c a n t l y in t o t a l d a i l y g ra z in g
h ours.
The o v e r a l l b r e e d t y p e m eans w e re 11.3 ± «2, 11.3 ± «2, 11.4
+ .2 and 11.2 + .2 f o r BH, TH, T(SH) and C(SH) c o w s, r e s p e c t i v e l y .
Table 9«
L e a s t- s q u a r e s a n a l y s i s o f v a r ia n c e f o r t o t a l d a i l y g ra z in g
time (1986)
Mean s q u a re s
( h r /d
Source
df
Breed type
3
1.18
Cow(breed)
20
4.31*
I
36.84*
L in e a r r e g r e s s i o n
1.11
581
R esidual
.17
R2
P< .05
B re e d t y p e s w e re t e s t e d f o r d i f f e r e n c e s among l e v e l o f g r a z i n g
i n t e n s i t y and no b r e e d d i f f e r e n c e s (P>.10) w e re f o u n d f o r e i t h e r
i n t e n s i t y a s i n 1985.
None o f t h e p r o d u c t i o n c o v a r i a t e s o r c a l f s e x
were s i g n i f i c a n t i n e x p la i n in g v a r i a t i o n in g ra z in g tim e , a s was found
i n 1985.
F i g u r e 6 i l l u s t r a t e s t h e e f f e c t o f day on t o t a l d a i l y g r a z i n g
tim e .
As th e season p ro g re s se d from day 215 to day 260 d a i l y g ra z in g
tim e in c r e a s e d from a p p ro x im a te ly 11 to 11.5 h r/d .
12 h r
fa tig u e
lim it
p ro p o s e d
by
S to b b s
T h is i s below t h e
(1 9 7 5 ).
The fo r a g e a v a i l a b i l i t y e s t i m a t e s f o r 1986 a r e p re s e n te d i n Table
10.
Forage a v a i l a b i l i t y o f g r a s s e s ,
which a r e th e p rim ary component
33
r = .17 (pc.01)
A A
3
230
;
JULIAN DAY
Figure 6. Effect of day of the year on total daily grazing time
during 1986. Triangles indicate daily grazing means.
34
o f t h e r a n g e cow’s d i e t ,
r e m a in e d f a i r l y
c o n s t a n t and a c t u a l l y
in c r e a s e d in th e l a t t e r p a r t o f th e stu d y .
T h i s w as p r o b a b l y t h e
re a so n f o r no l a r g e in c r e a s e i n g r a z in g tim e as was o bserved i n 1985.
Forage a v a i l a b i l i t y was probably a d eq u a te t o meet in ta k e demands,
so
f a t i g u e l i m i t s were n o t re a ch e d .
Table 10.
Forage a v a i l a b i l i t y f o r g r a s s e s , f o r b s and sh ru b s (1986)
G rasses
(k g /h a)
Day
Forbs
(kg/ha)
Shrubs
(k g /h a)
.
218 - 225
890.3
454.9
58.7
237 - 241
853-3
240.2
13.6
246 - 254
967.4
214.7
9 .8
Time o f Day Grazing
The l e a s t - s q u a r e s a n a l y s i s o f v a r i a n c e f o r t i m e o f day g r a z i n g
i s p re s e n te d i n Table 11.
Table 11.
L e a s t- s q u a re s a n a l y s i s o f v a ria n c e f o r tim e o f day g ra z in g
( 1986 )
Mean s q u a re s
Source
df
Breed ty p e
3
Grazing tim e p e rio d
7
Cow(breed)
R esid u al
.3
390.4*
20
.5
5042
.4
.56
R2
v
(h r)^
P< .05
35
Breed ty p e was n o t s i g n i f i c a n t f o r tim e o f day g ra z in g a s was r e p o r te d
i n 1985.
F i g u r e 7 sh o w s t h e o v e r a l l t i m e o f day g r a z i n g m eans.
The
m a jo r p e r i o d s o f g r a z i n g o c c u r r e d fro m 6 0 0 -9 0 0 h r and 1800-2100 h r ,
th e same m a jo r g ra z in g p erio d s, r e p o r te d i n 1985.
B i t e Rate
The l e a s t - s q u a r e s a n a l y s i s o f v a r ia n c e f o r b i t e r a t e i s l i s t e d i n
Table 12.
An av erage of 21 o b s e r v a tio n s p e r cow was ta k e n t h i s y e a r.
B re ed was. s i g n i f i c a n t i n t h e b i t e r a t e a n a l y s e s (P < .05).
The l e a s t -
s q u a r e s m eans f o r b i t e r a t e w e re 56.9 + 1.1 , 58.7 + 1.1 , 60,9 + 1.0
and 59.0 + 1.1 f o r BH, TH, T(SH) a n d C(SH) co w s, r e s p e c t i v e l y .
The
T(SH) b i t e r a t e was h i g h e r t h a n t h e HH b i t e r a t e (P<.10) b u t d i d n o t
d i f f e r fro m t h e TH o r C(SH), and TH and C(SH) d i d n o t d i f f e r fro m t h e
HH b r e e d
ty p e
(P > .1 0 ).
The T(SH) b r e e d t y p e h a d h i g h e r m i l k
p ro d u c tio n and c a l f w e ig h ts th a n th e HH breed type and probably h ig h e r
i n ta k e which would h e lp e x p la in t h e b i t e r a t e d i f f e r e n c e .
Time o f day i n w h ic h t h e b i t e r a t e o b s e r v a t i o n s w e re t a k e n w as
n o t a s i g n i f i c a n t s o u r c e o f v a r i a t i o n a s i t was i n 1985.
O b serv ers
d i d d i f f e r i n b i t e r a t e o b s e r v a t i o n s b u t t h e r e w as no s i g n i f i c a n t
o b s e r v e r x b re e d i n t e r a c t i o n .
Observer 2 re p o r te d h ig h e r b i t e r a t e s
t h a n d i d o b s e r v e r I , 59.7 + .5 and 58.1 + .5 b i t e s / m i n , r e s p e c t i v e l y .
T his was t h e same ra n k in g found i n 1985.
Breed x l i n e a r r e g r e s s i o n
i n t e r a c t i o n was n o n s i g n i f i c a n t (P>.10)
so r e g r e s s i o n s w ere pooled a c r o s s b reed ty p e s and F ig u r e 8 shows t h e
e f f e c t o f day on b i t e r a t e .
As season p ro g resse d from day 210 to 255
b ite r a te decreased lin e a r ly .
The f o r a g e a v a i l a b i l i t y was f a i r l y
c o n s is te n t o r in c r e a s in g d u rin g t h i s g ra z in g p e rio d .
I t has been
36
3-1
TIME OF DAY (x 1 0 0 )
Figure 7. Time of day grazing during 1986.
letters differ (P<.05).
Bars with different
37
Table 12.
L e a s t- s q u a r e s a n a l y s i s o f v a r ia n c e f o r b i t e r a t e (1986)
Mean s q u a re s
( b it e s /m in ) ^
Source
df
Breed ty p e
3
320 .2+
Cow(breed)
20
1 34.O6
Time o f day
I
Observer
I
284.4*
L in e a r r e g r e s s i o n
I
24397.4*
.1
466
R esidual
54.9
.54
R2
+ P<.10
* P<.05
shown t h a t b i t e r a t e in c r e a s e s w ith d e c li n in g fo r a g e a v a i l a b i l i t y and
t h i s y e a r t h e r e was
s te a d y o r i n c r e a s i n g fo ra g e a v a i l a b i l i t y so b i t e
r a t e may have t h e o p p o s ite re sp o n se .
The p r o d u c t i o n c o v a r i a t e s and c a l f s e x w e re t e s t e d f o r t h e i r
e f f e c t on b i t e r a t e but none were found s i g n i f i c a n t (PX10).
D ista n c e T rav eled
The l e a s t - s q u a r e s a n a l y s i s o f v a r ia n c e f o r d i s t a n c e t r a v e l e d i s
p re s e n te d i n Table 13. An average o f 4 pedom eter r e a d in g s p e r cow were
ta k e n t h i s y e a r.
B re e d was n o t s i g n i f i c a n t i n t h i s a n a l y s i s .
b r e e d t y p e m eans w e re 3-5 ± .4 , 3-8 + .4 , 3-6
f o r RH, TH, T(SH) and C(SH), r e s p e c t i v e l y .
The
+ .4 and 3»6 + .4 km /d
None o f t h e p r o d u c t i o n
c o v a r i a t e s , c a l f s e x o r l i n e a r o r q u a d r a t i c r e g r e s s i o n on day w e re
38
Y = 197.75 - .59X
3
230
2
JULIAN DAY
Figure 8. Effect of day of the year on bite rate during 1986.
Triangles indicate daily bite rate means.
39
s i g n i f i c a n t i n t h i s a n a ly s e s (PX10).
T a b le 13.
L e a st-sq u a re s a n a ly s is o f v a ria n ce f o r d is ta n c e tra v e le d
( 1986 )
Mean s q u a r e s
(km/d)*
df
Source
3
.2
Cow(breed)
20
1.5*
R esidual
70
.4
Breed type
i
.56
R2
ti P< .05
S p e c u la tio n and F u tu re D ir e c tio n
The m a j o r o b j e c t i v e o f t h i s s t u d y was t o e v a l u a t e t h e g r a z i n g
b e h a v i o r o f d i f f e r e n t b i o l o g i c a l t y p e s o f b e e f c a t t l e on r a n g e l a n d .
B i t e r a t e was o f p a r t i c u l a r i n t e r e s t because
past research in d ic a ted
no d i f f e r e n c e s i n d a i l y g ra z in g tim e o r d i s t r i b u t i o n of g ra z in g but
d i f f e r e n c e s i n i n t a k e w e re fo u n d on t h e same b r e e d t y p e s ( L a t h r o p ,
1985; W agner e t a l . , I 986).
We w e r e
in te re ste d
in
u n d e r s t a n d i n g how a n i m a l s e x p r e s s
d i f f e r e n c e s in b e h a v io r to a c h ie v e d i f f e r e n t q u a n t i t i e s of fo ra g e
in ta k e .
B i t e r a t e i s a m e a s u r e o f g r a z i n g b e h a v i o r w h ic h d i f f e r s among
d i f f e r e n t b i o l o g i c a l ty p e s o f b e e f c a t t l e and may be r e s p o n s ib le f o r
d if f e r e n t in ta k e le v e ls .
The i n t a k e d a t a m e a s u re d by F r e d r i c k s o n
(1986) show ed no d i f f e r e n c e s i n i n t a k e among BH, AH, 1 S I H and 3S1H
40
cows on a p e rc e n ta g e o f body w eight b a s i s d u rin g 1985.
The r e s e a r c h
on g r a z i n g b e h a v i o r show ed a t e n d e n c y (P=.10) f o r AH cows t o g r a z e
l o n g e r t h a n HH and ISIH cows b u t n o t d i f f e r e n t fro m 3S1H cow s.
d i f f e r e n c e s were s m a ll and may n o t be b i o l o g i c a l l y s i g n i f i c a n t .
The
B ite
r a t e was h i g h e s t f o r t h e 3S1H b r e e d t y p e and l o w e s t f o r t h e HH b r e e d
ty p e .
The i n t a k e v a l u e s do n o t h e l p t o a n s w e r q u e s t i o n s c o n c e r n i n g
t h i s fin d in g .
T his
The I SI H r a n k e d h i g h e s t i n i n t a k e and t h e HH l o w e s t .
s t u d y and t h e s t u d y done by F r e d r i c k s o n (1986) w e re done i n
d i f f e r e n t s i z e p a s t u r e s u s i n g d i f f e r e n t cows and d i f f e r e n t s to c k in g
r a t e s ; th e t e r r a i n o f the p a s t u r e s was a ls o d i f f e r e n t .
I t i s p o s s ib le
th a t th e se re p o rte d in ta k e v a lu e s a re not r e p r e s e n ta tiv e of th e
b e h a v i o r cow s.
I n 1986 F r e d r i c k s o n a l s o fo u n d no d i f f e r e n c e s i n
in ta k e among th e d i f f e r e n t b reed ty p e s but t h e r e was a d i f f e r e n c e i n
b ite ra te .
In 1986 both th e in ta k e and b e h a v io r work was done on th e
same p a s t u r e u s in g t h e same cows.
d i f f e r e n t tim e s.
The s t u d i e s w ere however, done a t
The e f f e c t o f f e c a l b a g s on i n t a k e i s n o t w e l l
u n d e r s t o o d so t h e r e i s a p o s s i b i l i t y t h a t t h e i n t a k e v a l u e s a r e n o t
r e p r e s e n t a t i v e o f th e tim e th e b i t e r a t e o b s e r v a tio n s were tak en .
If
t h e i n t a k e v a l u e s a r e r e p r e s e n t a t i v e o f t h e cows a t t h e t i m e t h e
b e h a v i o r w ork was d o n e , i t may be p o s s i b l e t h a t b i t e
e x p la n a tio n fo r th e d i f f e r e n t b i t e r a te s .
s iz e i s th e
I f in ta k e = b i t e r a te x
b i t e s i z e , th e a n im a ls w ith a h ig h e r b i t e r a t e may have had a s m a l le r
b i t e s i z e , th u s keep in g in ta k e c o n s ta n t.
B ite s i z e may be an im p o rta n t unanswered q u e s tio n t h a t should be
a d d ressed .
Research te c h n iq u e s a r e l i m i t e d a t p r e s e n t bu t e l e c t r o n i c
e q u ip m e n t i s
b e i n g d e v e lo p e d
to
m e a s u re b o l u s
siz e
and num ber
(Forwood e t al.» 1985).
T his may be a te ch n iq u e t h a t could be used to
e s t i m a t e i n t a k e and g r a z i n g b e h a v i o r s i m u l t a n e o u s l y w i t h m in im a l
s tre ss
on t h e
a n im a l.
T his i s
im p o rta n t
because
th e
research
t e c h n i q u e s u s e d t o c o l l e c t d a t a f o r f o r a g e i n t a k e may a f f e c t an
a n i m a l ’s b e h a v i o r w h ic h c o u ld i n f l u e n c e c o m p a r is o n o f s t u d i e s o f
f o r a g e in ta k e and g ra z in g b e h a v io r .
The observed
r e l a t i o n s h i p o f g r a z in g tim e and b i t e r a t e i n 1986
i s n o t w e ll u n d e rsto o d .
r a te decreased.
G r a z in g t i m e i n c r e a s e d g r a d u a l l y and b i t e
I n 1986 f o r a g e a v a i l a b i l i t y r e m a in e d c o n s t a n t o r
i n c r e a s e d t h r o u g h o u t th e s t u d y .
Under s t a b l e o r i n c r e a s i n g f o r a g e
a v a i l a b i l i t y b o th b i t e r a t e and g r a z i n g t i m e w ould be e x p e c t e d t o
d e c li n e a s th e season p ro g re s se d .
Even though g ra z in g tim e in c r e a s e d
s l i g h t l y , t h e r a p i d f a l l i n b i t e r a t e may h av e b e e n g r e a t enough t o
cause a d e c re a s e i n in ta k e a s th e season p ro g resse d .
in ta k e , may be a f a c t o r o f fo ra g e a v a i l a b i l i t y .
T his d e c re a se i n
I f th e c a lv e s grazed
more b e c a u s e o f h i g h q u a n t i t i e s o f a v a i l a b l e f o r a g e th e y may h a v e
reduced
n u rs in g l e v e l s which would d e c re a s e t h e energy re q u ire m e n t o f
t h e cow.
A lso t h e cow s w e re i n l a t e r s t a g e s o f l a c t a t i o n when m i l k
p r o d u c t i o n i s d e c l i n i n g and e n e r g y r e q u i r e m e n t s a r e d e c r e a s i n g .
A
p o s s ib le re a so n why g r a z in g tim e in c r e a s e d may be t h a t th e cows were
spending more tim e s e a rc h in g f o r d e s i r a b l e p l a n t s t h a t w ere d e c re a sin g
i n a v a i l a b i l i t y a s th e season p ro g re s se d .
The r e s e a r c h
p re se n te d
in
th is
t h e s i s h a s a n s w e r e d some
q u e s ti o n s and l e f t some unanswered q u e s tio n s .
to examine a b e h a v io r a l
One o f o u r concerns was
c h a r a c t e r i s t i c t h a t may a llo w d i f f e r e n t ty p e s
o f b e e f cows t o consume d i f f e r e n t i n t a k e l e v e l s .
B ite r a te o ff e rs a
42
p o s s i b l e e x p la n a tio n s in c e d i f f e r e n t b reed ty p e s e x h i b i t e d d i f f e r e n t
b ite ra te s.
Grazing tim e d id no t d i f f e r among gen o ty p es.
One might
s p e c u l a t e t h a t g r a z i n g t i m e i s a f u n c t i o n o f s o c i a l b e h a v i o r and
e n v iro n m e n ta l f a c t o r s such as
day l e n g t h and f o r a g e a v a i l a b i l i t y .
,This r e s e a r c h may n o t be a p p l i c a b l e a lo n e bu t when compared w ith o th e r
r e s e a r c h on f o r a g e in ta k e and p ro d u c tio n i t may be an im p o r ta n t l i n k
fo r
in c re a sin g
ra n g e la n d s .
th e
e ffic ie n c y
of p ro d u c tio n o f b e e f
c a ttle
on
43
SUMMARY
The summer g r a z i n g b e h a v i o r o f b e e f c a t t l e g r a z i n g m o u n ta in
f o o t h i l l r a n g e l a n d was s t u d i e d i n t h e s u m m e r's o f 1985 and 1986,
T w e n ty -fo u r a n im a ls w ith 6 a n im a ls p e r b reed group
year.
w e re u s e d e a c h
I n 1985 t h e f o u r b r e e d g r o u p s c o n s i s t e d o f H e r e f o r d (HH), 50%
Angus-50% H e r e f o r d (AH), 50% S im m en ta l-5 0 % H e r e f o r d (1S1H) and 75%
Simmental-25% H ereford (3S1H).
In 1986 th e breed groups c o n s is te d o f
(HH), T a r e n t a i s e - H e r e f o r d (TH), T a re n ta is e -S im m e n ta l-H e re fo rd (T(SH))
and C h a ro la is-S im m e n ta l-H e re fo rd (C(SH)).
The g r a z i n g b e h a v i o r v a r i a b l e s m e a s u re d w e r e g r a z i n g t i m e ,
d i s t a n c e t r a v e l e d and b i t e r a t e .
The b a s ic s t a t i s t i c a l model in c lu d e d
b reed ty p e , c a l f sex, cow(breed x c a l f se x ), th e l i n e a r and q u a d r a tic
r e g r e s s i o n s on day
and th e b re e d x r e g r e s s i o n i n t e r a c t i o n w h e n e v e r
b reed ty p e was s i g n i f i c a n t .
t e s t breed ty p e .
average
Cow(breed) was used a s t h e e r r o r term to
The p r o d u c t i o n c o v a r i a t e s
w e ig h tih e ig h t r a t i o ,
average
( a v e r a g e cow w e i g h t ,
c a l f w e ig h t,
average m ilk
p r o d u c t i o n , cow c o n d i t i o n s c o r e , c a l f c o n d i t i o n s c o r e and c a l f a g e )
w e re a l s o t e s t e d f o r t h e i r e f f e c t on t h e d e p e n d e n t v a r i a b l e s .
sex
w as
a lso
te ste d
as
an in d e p e n d e n t
v a ria b le .
None o f
C alf
th e
c o v a r i a t e s o r c a l f sex were s i g n i f i c a n t i n any o f th e a n a ly s e s.
The o v e r a l l d a i l y g ra z in g mean i n 1985 was 11.9 h r /d .
The l e a s t -
s q u a r e s means f o r t o t a l d a i l y g r a z i n g t i m e w e re 1 1 . 8 + .2 , I 2.3 + . 2 ,
11.6 + .2 and 11.6 + ,5 h r / d f o r HH, AH, ISIH and 3S1H, r e s p e c t i v e l y .
T h e re w as a t e n d e n c y (P = .1 0) f o r AH t o g r a z e l o n g e r t h a n HH and ISIH
bu t n o t lo n g e r th a n 3S1H (P>.10).
from 600-900 h r and .1800-2100 hr.
The m ajor g ra z in g p e rio d s o c c u rre d
B reed t y p e m eans f o r b i t e r a t e i n I 985 w e re 52.7 ± 1 . 5 » 56.2 +
1 .5 ,
53-2 + 1.4 and 59.0 ± 1.6 b i t e s / m f o r BH, AH,
re sp ec tiv e ly .
ISIH and 3S1H,
The 3S1H had a h ig h e r b i t e r a t e (P<.05) th a n th e HH and
I SIH b u t d i d n o t d i f f e r fro m t h e AH (P>.10). The AH h a d a h i g h e r b i t e
r a t e (P<.05) t h a n t h e
ISIH and HH b u t t h e ISIH and HH d i d n o t d i f f e r
(P > .1 0 ).
The b reed ty p e means f o r d is ta n c e t r a v e l e d i n 1985 were 3.1 ± .2,
3.4 + .2 , 4.0 + .2 and 2.8 ± .2 km /d f o r BH, AH,
ISIH and 3S1H,
resp ec tiv e ly .
The I SI H t r a v e l e d f a r t h e r (P<.10) th a n t h e o th e r t h r e e
b reed ty p e s.
The AH t r a v e l e d f a r t h e r (P<.10) t h a n t h e 3S1H b u t d i d
n o t d i f f e r from th e BH.
I n I 986 t h e mean d a i l y g r a z i n g t i m e was 11.3 h r / d and no b r e e d
type d i f f e r e n c e s w ere found. The b reed ty p e means w ere 11.3 + .2, 11.3
+ .2 ,
11.4 + .2 and
re sp ec tiv e ly .
11.2 + .2 h r / d
f o r BH,
TH,
T(SH) and C(SH),
Major g ra z in g p e rio d o c c u rre d from 600-900hr and 1800-
2100 h r .
Breed ty p e was s i g n i f i c a n t i n t h e b i t e r a t e a n a l y s i s i n 1986 and
m eans w e re 56.9 + 1 .1 , 58.7 ± 1 .1 , 60.9 ± 1.0 and 59.0 + 1.1 b i t e s / m
f o r BH, TH, T(SH) and C(SH), r e s p e c t i v e l y .
The T(SH) had a h i g h e r
j
b i t e r a t e th a n th e HH (P<.10) but d id n o t d i f f e r from TH or C(SH), and
TH and C(SH) d i d n o t d i f f e r fro m HH (P > .1 0 ).
No breed type d i f f e r e n c e s were found i n d i s t a n c e t r a v e l e d i n 1986
(P > .1 0 ).
The b r e e d t y p e m eans w e re 3.5 + .4 , 3»8 + .4 , 3.6 + .4 and
3 .6 + .4 km /d f o r BH, TH, T(SH) and C(SH), r e s p e c t i v e l y .
From t h e r e s u l t s o f t h i s r e s e a r c h , b i t e r a t e a p p e a r s t o be a
b e h a v io r a l e x p re ssio n ' by which p o t e n t i a l l y h i g h p r o d u c i n g b e e f cows
45
c o u ld i n c r e a s e i n t a k e and g r a z i n g t i m e a p p e a r s t o be i n d e p e n d e n t o f
breed t y p e .
46
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