Physiological and behavioral responses of cows on Montana foothill range to winter and supplement
by Roger William Dunn
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in
Range Science
Montana State University
© Copyright by Roger William Dunn (1986)
Abstract:
Supplementation of gestating beef cows spending the winter on range has shown benefits to cow
productivity. In order to understand how these benefits operate, detailed studies of the nutritional costs
for cows on winter range, and the effects of supplements, are necessary. As part of that research goal, a
study was conducted in 1984 and 1985 that recorded the grazing and travel behavior, and estimated the
forage intake, of gestating crossbred cows onwinter range receiving protein supplement. The rangeland
available to the cows contained cool season grasses dominated by bluebunch wheatgrass (Agropvron
snicatum (Pursh) Scribn. & Smith). The study pasture contained 324 hectares in the northwest foothills
of the Madison Range of southwest Montana. The cows wore vibracorders and pedometers for 48
continuous days in January and February. Daily intake was estimated using the chromic oxide dilution
technique. Correction factors for these- estimates were derived by determining chromic oxide-recovery
and by comparing the estimates to total fecal collection. Cow age had a significant (p<.05) effect on
daily grazing time, but not on daily intake. Cows receiving supplement showed significantly higher
intake (p<.05) than unsupplemented cows, but spent the same or less time grazing; Protein
supplementation seems to have lowered the nutritional cost of obtaining forage. Daily temperature
swings brought about adjustments in the cows' daily grazing schedule. Severe temperature changes also
brought short term reductions in daily grazing time. During these periods the cows may have been
experiencing acute cold stress. No consistent correlation between grazing time, past grazing time,
present temperature, and past temperature was found. This led to the conclusion that in 1 984 and 1985
the cows did not experience chronic cold stress, and were not forced to re-acclimate, even though
temperature varied between 8 and -26 degrees Celcius. PHYSIOLOGICAL AND BEHAVIORAL RESPONSES
OF COWS ON MONTANA FOOTHILL RANGE
TO WINTER AND SUPPLEMENT
by
Roger W i ll i a m Dunn
A th e s is submitted in p a r t i a l f u lf i llm e n t
o f t h e r e q u i r e m e n t s f o r t h e d eg r ee
of
Master of S c ie n c e
!
in
Range S c i e n c e
MONTANA STATE UNIVERSITY
Bozeman, Montana
March, 1986
/V37£
ii
APPROVAL
o f a t h e s i s s u b m i t t e d by
Roger W i ll i am Dunn
T h i s t h e s i s h a s been r e a d by each member of t h e t h e s i s c o m m it te e
and ha s been fo und t o 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,
f o 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 i s t e n c y , and i s r e a d y
f o r s u b m i s s i o n t o th e C o ll eg e o f G r a d u a te S t u d i e s .
Date
C h a i r p e r s o n , G r ad u at e Committee
Approval f o r t h e Major Department
___ V
Date
w
V?
Vc V % G>
Head, Major Department
Approved f o r th e Co ll ege o f G rad u ate S t u d i e s
Date
G r ad ua te Dean
iii
STATEMENT OF PERMISSION TO COPY
In
p resen tin g
th is
th e sis
in
p artial
fu lfillm en 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 o n t a n a 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 under t h e
r u l e s of t h e L i b r a r y .
B r i e f q u o t a t i o n s from t h i s t h e s i s a r e a l l o w a b l e
w ithout sp ecia l perm ission,
p r o v i d e d t h a t a c c u r a t e acknowledgement o f
s o u r c e i s made.
P e r m i s s i o n f o r e x t e n s i v e q u o t a t i o n from or r e p r o d u c t i o n o f t h i s
t h e s i s may be g r a n t e d by my m a jo r p r o f e s s o r ,
o r i n h i s a b s e n c e , by th e
D i r e c t o r o f t h e L i b r a r i e s when, i n t h e o p i n i o n of e i t h e r , t h e p r op os ed
use of 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 or use of
t h 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 i t h o u t my w r i t t e n p e r m i s s i o n .
Signature
Date
iv
ACKNOWLEDGEMENTS
I
wo uld l i k e t o e x p r e s s my a p p r e c i a t i o n t o t h e f a c u l t y and s t a f f
o f t h e D e p a r t m e n t o f A n im a l a n d Range S c i e n c e s ,
and th e
M o n ta n a
A g r i c u l t u r a l Experiment S t a t i o n .
The s t a f f a t t h e A n i m a l N u t r i t i o n L a b o r a t o r y , e s p e c i a l l y Nancy
Roth and Kent W i l l i a m s ,
gave a s s i s t a n c e and p a t i e n c e when b o th were
v e r y much needed, and v e r y much a p p r e c i a t e d .
I
My t h a n k s t o them.
would l i k e t o t h a n k J e s s Miner f o r b e i n g o u t t h e r e w i t h me and
r e m a i n i n g my f r i e n d t h r o u g h i t a l l .
He w i l l n ev er be f o r g o t t e n .
My t h a n k s t o S h a n n o n Q u i n s e y f o r h e r s i g n i f i c a n t ( p < . 0 I ) h e l p
w i t h s t a t i s t i c s and SAS.
Without h e r h e l p P d s t i l l be h e r e .
T h e r e a r e tw o men I h a v e t h a n k e d o f t e n a n d w i t h -the u t m o s t
s i n c e r i t y . I do so a g a i n now, b u t I ’m s u r e t h i s w i l l n o t be t h e l a s t
tim e.
S pecial
thanks
to
K ris
H avstad
an d
Eldon
e n c ou r a ge , h e l p , and a l l o w me t o be and do my b e s t .
Ayers.
Such a g i f t means
m o r e t o me t h a n I c a n s a y , a n d I am h o n o r e d t o be i t s r e c i p i e n t .
friends,
you’r e welcome by my f i r e a n y t i m e ,
y o u r s warm me.
They
My
and t h a n k you f o r l e t t i n g
,
And f i n a l l y , s i n c e r e t h a n k s t o my f a m i l y , e s p e c i a l l y my m o t h e r
a n d f a t h e r , S a r a h a n d L a r r y Dunn, a n d my b r o t h e r a n d s i s t e r - i n - l a w ,
Barry
a nd J a n e Dunn,
remember w here home i s .
for
th eir fa ith
i n me,
and f o r
h e l p i n g me
V
TABLE OF CONTENTS
LIST OF TABLES............................................................................................ ....................
Page
vi
LIST OF FIGURES............................................................................................................. ..
viii
ABSTRACT............................................................................................................................
ix
INTRODUCTION...............................
I
LITERATURE REVIEW...........................................................................................................
3
I n t a k e o f W in te r F o r a g e ................................................
W in te r a s i t A f f e c t s Metabolism and N u t r i t i o n .................................
Pregnancy as i t A f f e c t s D i e t a r y Requi rem ent s and I n t a k e . . . .
S u p p l e m e n t a t i o n a s i f A f f e c t s W in te r Forage I n t a k e ...................
I n t a k e B e h a v i o r ............................................................................................
3
8
14
16
23
MATERIALS AND METHODS.................................................................................................
28
Study S i t e D e s c r i p t i o n ....................................................................................
G r a z in g Management................
I n t a k e Measurement.............................................................................................
B eh a v i o r E v a l u a t i o n ..........................................................................................
Data A n a l y s i s ..................................................................................
28
29
29
34
35
RESULTS..................................................................... ........................................................
38
1984 T r i a l ..................................................................................
Body Weight and C o n d i t i o n S c o r e ........................................................
G r az in g B e h a v i o r ..........................................................................................
I n t a k e ..................
1985 T r i a l .........................................................................................................
Body Weight and C o n d i t i o n S c o r e ..................
G r az in g B e h a v i o r ..........................................................................................
I n t a k e ...............................................................■.................................................
38
38
38
42
44
44
45
50
DISCUSSION...........................................................................................................................
53
. Forage U t i l i z a t i o n and F o r a g in g P a t t e r n s ............................................
E n v i r o n m e n ta l S t r e s s . . . . . ............................................................................
Forage I n t a k e ........................................................................................................
53
54
57
SUMMARY.................................................................................................................
61
RECOMMENDATIONS AND QUALIFICATIONS...................................................................
63
LITERATURE CITED.............................................................................................................
66
APPENDIX...............................................................................................................................'
78
vi
LIST OF TABLES
Ta b le
1
2
3
4
5
6
7
8
9
10
11
12
Page
S e a s o n a l c o m p o s i ti o n o f r an ge g r a s s e s i n e a s t e r n Montana
and n o r t h e r n U ta h ................................... ............................... ............. .........
4
A ppa ren t d i g e s t i b i l i t y of g r a s s c o n s t i t u e n t s d u r i n g .
summer and w i n t e r i n U tah ............ .................... ...................... ...............
g
P r e d i c t e d g r a z i n g time o f cows a t v a r i o u s t e m p e r a t u r e s
and wind v e l o c i t i e s .....................................................................................
25
S i g n i f i c a n t c o r r e l a t i o n c o e f f i c i e n t s between c a t t l e
a c t i v i t i e s and w e a th e r p a r a m e t e r s .....................................................
26
Supplement c o m p o s i ti o n f o r w i n t e r , 1985 a t Red B l u f f
R es ear ch Ranch, N o r r i s , Montana..................................................
E s t i m a t i o n o f f e c a l o u t p u t and f o r a g e i n t a k e f r o m f e c a l
g r a b s a m p l e s ..................................................................... ...................... ..
R e g r e s s i o n model f o r e x p l a i n i n g v a r i a t i o n i n th e d a i l y
time s p e n t g r a z i n g d u r i n g w i n t e r ..........................................................
Time s e r i e s a n a l y s i s of d a i l y g r a z i n g time bas ed on p a s t
g r a z i n g t i m e s and p r e s e n t and p a s t t e m p e r a t u r e s ............ ..
D a ily g r a z i n g t i m e s and d i s t a n c e s t r a v e l e d f o r 3
cow age groups., I 9 8 4 . .................................................. , . . . .............
Stepwise l i n e a r r e g r e s s i o n of d a i ly grazing time, 1984 ...
31
33
36
37
39
43
Time s e r i e s a n a l y s i s o f t o t a l d a i l y g r a z i n g t i m e and
av e r a g e d a i l y t e m p e r a t u r e , 1984.....................................
T o t a l d a i l y i n t a k e (0MB %BW) e s t i m a t e d from g r a b samp les
and a d j u s t e d f o r Cr2 Og r e c o v e r y , 1984.................................. ..
43
44
13
Linear r e g r e s s i o n of d a i ly t o t a l in ta k e as r e l a t e d to
d a i l y g r a z i n g t i m e , 1984. . . . . ....................................................................44
14
D a i l y g r a z i n g t i m e s and t r a v e l o f each t r e a t m e n t group,
1985...........................................................................................................................
15
S te p w ise l i n e a r r e g r e s s i o n o f d a i l y g r a z i n g t i m e , 1 9 8 5 . . .
16
Time s e r i e s a n a l y s i s of t o t a l d a i l y g r a z i n g time and
av e r a g e d a i l y t e m p e r a t u r e , I 985..........................................
46
49
50
v ii
L IS T OF TABLES -
C o n tin u e d
Tablfe
Page
17
D a i l y f o r a g e o r g a n i c m a t t e r i n t a k e (%BW), 1985........................
51
18
L i n e a r r e g r e s s i o n o f d a i l y t o t a l i n t a k e , 1985.............. ....
52
APPENDIX
19
Body w e i g h t s and c o n d i t i o n s c o r e s f o r 5 cow age g r o u p s .
1984..................... ........................ ...................................... .................................... yg
20
Body w e i g h t s and c o n d i t i o n s c o r e s f o r 4 cow age g r o u p s ,
1 9 8 5 . ............................................................................ ..................................... ..
79
Body w e i g h t s and c o n d i t i o n s c o r e s f o r each t r e a t m e n t
g ro u p , 1985............................................................................ ...................... ..
80
21
22
D a i l y g r a z i n g t i m e s and d i s t a n c e s t r a v e l e d f o r f o u r cow
age g r o u p s ,
1985................................................ ........................... ............... 80
23
Chromic o x id e r e c o v e r y (% f e d ) , 19 85 ....................... ......................... 81
24
D a i l y f e c a l o u t p u t (0MB %BW) e s t i m a t e d u s i n g t o t a l
f e c a l c o l l e c t i o n and Cr2 Og, I 985.......................................................... Si
25
T o t a l d a i l y i n t a k e (0MB %BW), 1985..................................................... 82
v iii
L IS T OF FIGURES
Figure
1
Page
Heat p r o d u c t i o n a s r e l a t e d t o t h e th e rm al e n v ir o n m en t
of b e e f c a t t l e .................................................................................................
2
Heat p r o d u c t i o n and co l d a d a p t a t i o n i n b e e f c a t t l e ............
3
A normal w i n t e r t e m p e r a t u r e p a t t e r n and t h e a s s o c i a t e d
g r a z i n g a c t i v i t y . ............................................................
4
i
11
4
G raz in g a c t i v i t y a s s o c i a t e d w i t h t h e 1984 t r i a l ' s
c o l d e s t t e m p e r a t u r e s .........................................................
5
A warming t r e n d and t h e a s s o c i a t e d g r a z i n g a c t i v i t y . . . . . '
6
A t e m p e r a t u r e d e c l i n e and t h e a s s o c i a t e d g r a z i n g
a c t i v i t y .......................................................................
41
47
' APPENDIX
7
Chromic o x i d e r e c o v e r y p a t t e r n d u r i n g t o t a l f e c a l
c o l l e c t i o n , 1985..............................................................................................
o
83
ix
ABSTRACT
S u p p l e m e n t a t i o n o f g e s t a t i n g b e e f cow s s p e n d i n g t h e w i n t e r on
r a n g e h a s shown b e n e f i t s t o cow p r o d u c t i v i t y .
In order to understand
how t h e s e b e n e f i t s o p e r a t e , d e t a i l e d s t u d i e s o f t h e n u t r i t i o n a l c o s t s
f o r co w s on w i n t e r r a n g e , a n d t h e e f f e c t s o f s u p p l e m e n t s , a r e
n e c e s s a r y . As p a r t o f t h a t r e s e a r c h g o a l , a s t u d y was c o n d u c t e d i n
1984 a n d 1985 t h a t r e c o r d e d t h e g r a z i n g a n d t r a v e l b e h a v i o r , a n d
e s t i m a t e d t h e f o r a g e i n t a k e , o f g e s t a t i n g c r o s s b r e d co w s o n w i n t e r
r a n g e r e c e i v i n g p r o t e i n s u p p l e m e n t . The r a n g e l a n d a v a i l a b l e t o t h e
cows c o n t a i n e d cool s e a s o n g r a s s e s d o m i n a te d by bluebunch w h e a t g r a s s
( Agropyron s p ic a tu m (Pursh) S c rib n . & Smith).
The s t u d y p a s t u r e
c o n t a i n e d 324 h e c t a r e s i n t h e n o r t h w e s t f o o t h i l l s o f t h e Madison Range
o f s o u t h w e s t Montana.
The cows wore v i b r a c o r d e r s and p e d o m e te r s f o r
48 c o n t i n u o u s d a y s i n J a n u a r y and F e b r u a r y .
D a i l y i n t a k e w as
e s t i m a t e d u s in g the chrom ic oxide d i l u t i o n te c h n iq u e .
C orrection
f a c t o r s f o r these- e s t i m a t e s w ere d e r i v e d by d e t e r m i n i n g c h r o m i c oxider e c o v e r y a n d by c o m p a r i n g t h e e s t i m a t e s t o t o t a l f e c a l c o l l e c t i o n .
Cow a g e h a d a s i g n i f i c a n t (p <.05) e f f e c t on d a i l y g r a z i n g t i m e , b u t
n o t on d a i l y i n t a k e .
Cows r e c e i v i n g s u p p le m e n t showed s i g n i f i c a n t l y
h i g h e r i n t a k e (p<.05) t h a n u ns u p p le m en te d cows, but. s p e n t t h e same or
l e s s time grazing.
P r o t e i n s u p p l e m e n t a t i o n seems t o h av e l o w e r e d t h e
n u t r i t i o n a l co st of o b ta in in g fo ra g e . ■D aily te m p e r a tu r e swings
b r o u g h t a b o u t a d j u s t m e n t s i n th e cows’ d a i l y g r a z i n g s c h e d u l e .
Severe
te m p e r a t u r e changes a l s o brought s h o r t term r e d u c t io n s i n d a i l y
g ra z in g tim e.
D u r i n g t h e s e p e r i o d s t h e c o w s may h a v e b e e n
e x p e rie n c in g acu te cold s t r e s s .
No c o n s i s t e n t c o r r e l a t i o n b e t w e e n
g r a z i n g tim e , p a s t g r a z i n g tim e , p r e s e n t t e m p e r a t u r e , and p a s t
t e m p e r a t u r e w a s f o u n d . T h i s l e d t o t h e c o n c l u s i o n t h a t i n I 984 and
1985 t h e cows d i d n o t e x p e r i e n c e c h r o n i c c o l d s t r e s s , a n d w e r e n o t
forced to re -a c c lim a te ,
even though t e m p e r a t u r e v a r i e d betwe en 8 and
- 26 d e g r e e s C e l c iu s .
I
INTRODUCTION
I n many a r e a s o f w e s t e r n Montana snow blows f r e e from r a n g e l a n d ,
and f o r a g e i s a c c e s s i b l e t o c a t t l e y e a r round. However,
content
of forage
W inter range
varies
g reatly
c o n ta in in g m ature,
d e f i c i e n t i n some n u t r i e n t s ,
th e n u t r i e n t
among a r e a s a n d p l a n t
dormant g r a s s e s w i l l
species.
usually
be
and i s o f t e n i n a d e q u a t e t o m e e t t h e
n u t r i e n t r e q u i r e m e n t s o f p r e g n a n t b e e f cows ( e s p e c i a l l y a s p r o d u c e r s
t r y t o m a i n t a i n o r im pr o ve cow p r o d u c t i v i t y ) .
N u t r i e n t s u p p l e m e n t a t i o n f o r b e e f cows w i n t e r i n g on r a n g e l a n d h a s
b e e n s h o w n t o i m p r o v e cow p e r f o r m a n c e w i t h t h e a d d e d a n d d i r e c t l y
related
of
b e n e f i t of im pr ove d c a l f p er f o r m a n c e .
nutrien t
w asteful.
supplem entation
can
be
However,
p ro fitab le
or
th e p r a c t i c e
econom ically
The m o s t e f f e c t i v e s u p p l e m e n t f o r cows g r a z i n g w i n t e r
f o r a g e i s one t h a t w i l l a i d t h e rum en m i c r o b i a l p o p u l a t i o n i n i t s
d i g e s t i o n of t h e m a t u r e w i n t e r f o r a g e .
The most, e f f i c i e n t s u p p le m en t
i s one t h a t p r o v i d e s t h i s d i g e s t i v e a s s i s t a n c e w i t h o u t b e c o m i n o a
d ie ta r y s u b s t i t u t e fo r w in te r forage.
effectiv en ess,
efficiency,
In order to
and p r o f i t a b i l i t y
determ in e the
of a supplem ent,
a
p r e c i s e d e t e r m i n a t i o n o f t h e b i o l o g i c a l b e n e n i t s g a i n e d w i t h each u n i t
o f expense i s r e q u i r e d .
Such d e t e r m i n a t i o n s w i l l p r o v i d e i n f o r m a t i o n
f o r d e s i g n i n g o t h e r , more p r o f i t a b l e s u p p l e m e n t s .
This
study
was
a
segment
of
an
ongoing
research
project
i n v e s t i g a t i n g several param eters of w in te r c a t t l e n u t r i t i o n including
the b io lo g ic a l
b e n e fits of supplem entation.
This p o r t i o n of th e
p r o j e c t h a s c o n c e n t r a t e d on t h e i n t e r a c t i o n o f d i e t a r y s u p p l e m e n t a t i o n
and w i n t e r
forage
intake.
The s p e c i f i c o b j e c t i v e s i n c l u d e d
(I)
2
estim atio n
of
w in ter
forage
in tak e
of
b o t h s u p p l e m e n t e d and
u n s u p p l e m e n t e d cow s i n t h e t h i r d t r o m e s t e r o f g e s t a t i o n ,
an d ( 2 )
me as ur e m en t o f t h e b e h a v i o r a s s o c i a t e d w i t h w i n t e r f o r a g e i n t a k e of
both s u p p l e m e n t e d a n l u n s u pp le m en te d cows i n
gestation.
the t h i r d
trim ester
of
The s t u d y used A n g u s - c r o s s cows g r a z i n g f o o t h i l l r a n g e l a n d
t y p i c a l o f s o u t h w e s t Montana.
Major g r a s s e s on t h e s t u d y s i t e i n c l u d e
b l u e b u n ch u h e a t g r a s s ( A g r o p y r o n s p i c a t u m ( P u r s h ) S c r i b n . & S m i t h ) ,
n e e d l e a n d t h r e a d ( S t i p a , c o m a ta ’ T rin . & Rupr.), Id ah o f e s c u e ( F e s t u c a
id a h o e n s is Elm er),
a n d 'b a s in w ildrye
(E l v m u s c i n e r e u s
S cribn.
&
Mmrr. ) .
Funding
for
the
study
was p r o v i d e d . j o i n t l y
by t h e
A g r i c u l t u r a l Expe rim ent S t a t i o n and Montana S t a t e U n i v e r s i t y .
M o nt an a
3
LITERATURE REVIEW
Any s t u d y of th e b e n e f i t s o f s u p p l e m e n t a t i o n must be l i m i t e d i n
scope t o a l l o w s o l u t i o n s t o be a p p l i e d t o a s p e c i f i c s i t u a t i o n .
This
s t u d y was l i m i t e d t o c r o s s b r e d cows i n t h e l a s t t r i m e s t e r o f g e s t a t i o n
(w in te r m onths),
Montana,
grazing n ativ e f o o th i ll
rangeland in
and r e c e i v i n g a p r o t e i n s u p p le m e n t.
lim itatio n s
behavior.
h a s a n e f f e c t on t w o v a r i a b l e s ,
The f o l l o w i n g l i t e r a t u r e
lim itatio n ,
th eir
in teractio n s,
review
and
th e ir
southw est
Each o f t h e a b o v e
i n t a k e an d f o r a g i n g
w ill
deal
effects
w ith
on
each
the
tw o
variables.
I n t a k e o f Wi nte r Forage
Forage
av ailab le
n u tr itio n a l q uality.
shrubs
for
w in ter
grazing is
generally
The n u t r i e n t c o n t e n t o f g r a s s e s ,
o f low
forbs,
and
c h a n g e s s e a s o n a l l y , w i t h mi nim um l e v e l s o f s u c h i m p o r t a n t
n u t r i e n t s a s p r o t e i n , phosp ho rou s, and c a r o t e n e o c c u r i n g i n t h e w i n t e r
(Cook a nd H a r r i s 1 950b ,
M ars h e t a l .
1959).
u s u a l l y low i n p r o t e i n d u r i n g t h e w i n t e r ,
energy to c a t t l e i f
H a r r i s 1968b,
th e y may p r o v i d e s u f f i c i e n t
c o n s u m e d i n l a r g e e n o u g h q u a n t i t i e s (Cook a n d
C la n to n 1981).
;
A lthough g r a s s e s a r e
'
S e a s o n a l l e v e l s o f i m p o r t a n t components
■
!
o f g r a s s e s h a v e b e e n m e a s u r e d i n U t a h an d M o n ta n a (Cook an d H a r r i s
19 5 0 a,
1 968b ;
levels
are
M ar s h e t a l .
in
w inter
Lignin
w hile
o th e r n u t r i e n t l e v e l s , e s p e c i a l l y crude p r o te i n , a re low er.
Along
than
in
and
Thes e
e a r l y summer,
higher
Table I .
1 965).
levels
generally
in
Van Dyne e t a l .
cellulose-
are
summarized
1959;
w i t h l o w n u t r i e n t c o n t e n t , m a t u r e d o r m a n t g r a s s e s a r e a l s o o f low
4
Tabl e
I„
S ea s o n al c o m p o s i t i o n o f r a n g e g r a s s e s i n
and n o r t h e r n ' Utah.
eastern
Montana
Time
Dec-Apr
Dormant
May-June
Immature-bloom
Component
Species
Years
Crude
Protein
%
Agropryon
s p i ca turn
19551957
2.7-3.4
10-15
S tipa
comata
19551960
1 . 9- 11 .2
11.3-14.7
Ii
19481953
3.5-6.0
9.0-17.0
grazing
sample
19481953
3.0-5.0
8 . 0- 20.0
Agropyron
s p ic a t u m
19551957
8.5-12.5
11. 0- 13.0
S tipa
comata
19551960
12.0-21.5
10.7-16.9
ran ge
grass
mix
1968
12.7
(Sept)
9 .7
Cook and
Harris
1968b
1950
12.5
( S e p t)
10.0
Cook and
Harris
1950a
Lignin
%
U
Citation
VanDyne
et al.
1965
it
Marsh e t
a l . 1959
ir
VanDyne
et al.
1965
Ir
Cellulose
%
Bromus
carinatus
1950
49.5-749.8
(Sept)■
42.7-43.1
Cook and
Harris
1950b
Ca ro te n e
m illigram
%
Agropyron
sp ic at u m
19551960
6 . 2- 5 8 .0
(Sept)
118 .4-1 36 .1
VanDyne
et al.
1965
Stipa
comata
19551960
1 . 0- 8 .3
6 3 . 4 -1 3 9. 1
Il
"
1948-
0-12.5
75.0-160.0
Marsh
et al.
1959
5
T a b le I .
c o n tin u e d
Time
Dec-Apr
Dormant
May-June
Immature-bloom
mS1953
0- 10.0
75.0-200.0
Marsh
et al.
1959
Agropyron
s p ic a t u m
19551957
0.0310.042
0.062-0.148
VanDyne
et al.
1965
S tipa
comata
19551960
0 . 0210.118
0.104-0.230
19481953
0.050.08
0.17-0.23
19481953
0.030.09
0.14-0.28
Component
Species
Years
Car ot ene
cont.
grazing
sample
Phosphorous
%
IT
grazing
sample
d ig estib ility
cellu lo se
due t o t h e
higher
(Cook a n d H a r r i s
le v e ls of
1968 b).
C itation
It
Marsh
e t al.
1959
!I
in d ig estib le
l i g n i n and
A com parison of the ap p are n t
d i g e s t i b i l i t y o f g r a s s e s i n summ er a n d w i n t e r c a n be f o u n d i n T a b l e
2.
Cook and H a r r i s
(1968b) s t r e s s e d t h e f a c t t h a t t h e c h e m ic a l
c o n t e n t s o f p l a n t s on w i n t e r r a n g e v a r i e d l i t t l e
months.
Van Dyne and Heady
constituents te ste d for,
season
(1965)
found
th at
over the w in te r
of
all
chem ical
l i g n i n v a r i e d l e a s t over t h e w i n t e r g r a z i n g
6
Tabl e 2.
Apparent d i g e s t i b i l i t y o f g r a s s c o n s t i t u e n t s d u r i n g
and w i n t e r i n Utah (from Cook and H a r r i s 1968b).
Digestion C o effic ien t %
Total
Protein
Gross
ener gy
summer
Metabo­
lizable
D i g e s t i b l e • ener gy
protein
(kcal/kg)
Time
Species
Summer
Agropyron
in te r m ed iu m
66.2
71 .4
62.4
7.3
2253
A g ro p yr o n.
in erm e
50.1
68.7
57.0
5. 2
1936
Agropyron
sm ithii
7 3 .8
64.0
61 .2
11.1
2028
Agropyron
inerme
0. 0
76.4
56.9
0. 0
1991
Agropyron
sm ithii
6.4
70.1
64 .3
0.2
2469
27.6
69 .7
50.7
1.2
1647
69.5
45 .9
0.3
1616
W in te r
Stipa
comata
O r y z o p s is
?
hymenoides
6. 4
:
Cellulose
I f c a t t l e r e l y on t h i s l e s s d i g e s t i b l e ,
less nutritio u s
more must be consumed t o o b t a i n n e c e s s a r y n u t r i e n t l e v e l s ,
t i m e and en er g y must be
Under t h e s e c o n d i t i o n s ,
rumen
and
th e
forage,
and
more
expended t o d i g e s t what th e y have consumed.
both the p h y sical cap acity of the
digestive
c a p a c i t y of t h e rumen
beco me l i m i t i n g ( C r a m p t o n I 952 ).
reticulo-
m i cr o b e • p o p u l a t i o n
This le a d s to d e c re a se d in t a k e ,
b e c a u se i n t a k e cannot ex ce ed o u tf l o w from th e rumen (p a s s a g e r a t e ) ,
and o u t f l o w i s dep endent on how f a s t t h e a n i m a l and i t s m i c r o b e s can
b r e a k down t h e consumed p l a n t m a t e r i a l . For w i n t e r f o r a g e h i g h i n c e l l
7
w all
c o n te n t d i g e s t i o n r a t e i s slow ed.
This re d u c e s o u tflo w
and
l e a v e s l a r g e am ounts of fo o d r e s i d u e s i n th e rumen i n t h e form of a
f l o a t i n g f i b e r ma t (Weston 1967, Jo n es 1972).
and f u r t h e r i n t a k e i s l i m i t e d
intake
The rumen r e m a i n s f u l l
( C a m p l i n g e t a l . 196 2) .
Dry m a t t e r
c a n i n c r e a s e o n l y i f an i n c r e a s i n g a m o u n t o f d r y m a t t e r i s
d i g e s t e d (Conrad e t a l .
1964).
',
t
I
M o n t g o m e r y ' a n d B a u m g a r d t (1 96 5) s t a t e d t h a t c a t t l e w i l l a d j u s t
t h e volume o f fo o d i n t a k e t o meet p h y s i o l o g i c a l en er g y demand i f rumen
fill
does not l i m i t
consum ption.
H ow e v er ,
f o r cow s g r a z i n g low
q u a l i t y w i n t e r f o r a g e r u m e n f i l l d o e s a p p e a r t o be t h e m a i n f a c t o r
l i m i t i n g i n t a k e ( B a l c h and C a m p l i n g 196 2, Grovum 1 96 9, J o u r n e t an d
Bemond 1976 , E l l i s 197 8) .
When t h e d i g e s t i b i l i t y o f f o r a g e i s l e s s
t h a n a p p r o x i m a t e l y 65 p e r c e n t , r u m e n f i l l i s f a i r l y c o n t i n u o u s , and
therefore
c o n t i n u o u s l y l i m i t i n g ( J o n e s 1972).
f o r a g e i n t a k e by c a t t l e ,
In a review
co n c e r n in g
C o r d o v a e t a l . ( 1 97 8 ) r e p o r t e d t h a t i n t a k e
e s t i m a t e s i n t h e w e s t e r n U n i t e d S t a t e s r a n g e f r o m 1.0 t o 2.8 p e r c e n t
o f body w e i g h t o r 40 t o 90 g dm/kg body w e ig h t .
study
at
Montana
S tate
U n i v e r s i t y ’s
In a previous w in te r
Red B l u f f
Research
Ranch,
e s t i m a t e d f o r a g e o r g a n i c m a t t e r i n t a k e r a n g e d from 0.8 t o 1.4 p e r c e n t
o f body w e i g h t ( T u r n e r 1985).
Und er t h e
f i l l - l i m i t i n g conditions
i m p o s e d by w i n t e r f o r a g e o f low q u a l i t y , d e c l i n i n g a v a i l a b i l i t y o f
such f o r a g e does n o t a p p e a r to l i m i t i n t a k e .
estim ated
quality,
the
intake
of
heifers
grazing
but d e c l i n i n g a v a i l a b i l i t y .
as th e q u a n t i t y of fo ra g e d ecre ase d ,
levels.
H a v s t a d e t a l . (1 98 3)
forage
of
c o n s t a n t low
H e if e r s in c re a s e d grazing time
and a c h i e v e d c o n s t a n t i n t a k e
8
Und er c i r c u m s t a n c e s w h e r e r u m e n f i l l
i s n o t th e main f a c t o r
l i m i t i n g i n t a k e , VFA ( v o l a t i l e f a t t y a c i d s ) , e s p e c i a l l y a c e t a t e a n d
propionate,
a p p e a r t o be i m p o r t a n t s i g n a l s u b s t a n c e s f o r t h e c o n t r o l
of in ta k e .
N e u r a l s e n s o r s f o r VFA a r e b e l i e v e d t o be l o c a t e d i n o r
n e a r t h e r u m e n , ( B a i l e a nd May er 1 968, B i n e s 1971) a n d i n t h e p o r t a l
v e i n ( B a i l e I 969 a s c i t e d i n B i n e s 1 9 7 1 ) . N e u r a l s i g n a l s a r e s e n t t o
t h e hy p o th a lm u s which i s t h e c e n t e r of t h e i n t a k e
(Conrad 1966).
c o n t r o l mechanism
As VFA l e v e l s go up, i n t a k e i s d e p r e s s e d (B h a t t a c h a r y a
and Warner 1968, B a i l e and F o rb es 1974, Anil and F or b es 1977).
K a r t c h n e r a n d Adams ( I 982) f o u n d l o w e r i n t a k e a n d h i g h e r r u m e n
VFA l e v e l s i n cows s u p p le m e n te d e v e r y o t h e r day vs. cows sup p le m en te d
e v e r y day i n t h e w i n t e r .
T h i s s u g g e s t s t h e VFA i n t a k e m e c h a n i s m i s
o p e r a t i n g d u r i n g t h e w i n t e r w i t h a lo w q u a l i t y r o u g h a g e d i e t .
But
J o n e s (1 972) p o i n t e d o u t t h a t l o w q u a l i t y r o u g h a g e d i e t s c o n t a i n i n g
h i g h l e v e l s o f l i g n i n a r e s l o w l y d i g e s t e d , and rumen VFA l e v e l s may be
to o low i n t h e s e
intake.
If
so,
c irc u m s ta n c e s to play a r o l e
in
the
control
of
o t h e r m e c h a n i s m s may be i n v o l v e d i n t h e r e s u l t s
r e p o r t e d by K a r t c h n e r and Adams (1982).
These a u t h o r s s u g g e s t e d t h a t
rumen c o n d i t i o n s i n t h e cows f e d g r a i n on a l t e r n a t e days may have been
l e s s favorable f o r f ib e r digestion.
Thi s c o n d i t i o n i s d i s c u s s e d i n a
l a t e r s e c t i o n of t h i s review.
W in te r a s i t A f f e c t s Metabolism and N u t r i t i o n
W i n te r h a s some s t r i k i n g p h y s i o l o g i c a l and b e h a v i o r a l e f f e c t s on
cattle.
C li m a t e can a f f e c t a r an ge cow's r e p r o d u c t i v e p e r f o r m a n c e and
m ilk p ro d u ctio n (B ellido e t al.
19 8 1 ).
E ffe c ts of environm ental
9
s t r e s s , i n c l u d i n g t h e en er gy c o s t o f g r a z i n g and w a l k i n g ,
can r a i s e an
a n i m a l s m a i n t a i n e n c e en er g y r e q u i r e m e n t 25 t o 50 p e r c e n t above t h a t of
a n i m a l ’s k e p t i n d o o r s ( O s u j i 197*0.
environment are s i g n i f i c a n t ,
A lthough th e e f f e c t s o f a cold
th e y a r e n o t a l w a y s e x c e s s i v e and do n o t
e x c l u d e p r o d u c t i v i t y ( e x p r e s s e d by cow w e i g h t ,
cow c o n d i t i o n ,
and
f e t a l g r o w th ) d u r i n g t h e w i n t e r (W eb s te r 1970a).
The most o b vi o u s e f f e c t o f t h e c o l d w i n t e r e n v i ro n m e n t i n v o l v e s
t h e f a c t t h a t heat, e m i s s i o n from t h e a n i m a l r i s e s a s t h e t e m p e r a t u r e
d r o p s ( B l a x t e r an d Wa in ma n 1 9 6 1 ) .
Heat i s l o s t th ro u g h r a d i a t i o n ,
c o n d u c t i o n , a n d e m i s s i o n o f w a t e r v a p o r ( B l a x t e r a n d Wainman 196 1) .
In
fact,
all
in d irectly ,
animal
physiologic
responses
to
cold r e l a t e ,
directly
or
to an i n c r e a s e i n th e r a t e of h e a t t r a n s f e r betw een an
and i t s e n v i r o n m e n t (C h r i s t o p h e r s o n and Young 1981).
Webster
(I 9 7 0 a , b) h a s sh o w n t h a t c a t t l e may g a i n r a d i a n t h e a t f r o m t h e s u n
d u r i n g t h e day; how ever,
r a d ia n t h e a t l o s s a t n ig h t outw eighs th e
g a i n b et w ee n November and March i n s o u t h e r n A l b e r t a , Canada.
This n e t
r a d i a n t h e a t l o s s h a s an i m p o r t a n t and i m m e d i a t e e f f e c t .
The an im al
must produce h e a t to
m ain tain
counteract
lo sses
in
order
to
homeothermy (Young and C h r i s t o p h e r s o n 1974).
Cold s t r e s s ,
of
exposure.
and t h e a n i m a l ’s r e s p o n s e s t o i t ,
D uring
acute
(short
conserves h e a t through p il o e r e c t io n ,
surface,
low ered r e s p i r a t o r y r a te ,
a n d s e e k i n g s h e l t e r ( S l e e 1971,
term )
cold
vary w ith d u ratio n
stress
an a n i m a l
v a s o c o n s t r i c t i o n a t the s k in
d e c r e a s e d w a t e r and f oo d i n t a k e ,
Young 1 975a* Gonyou e t a l .
1979).
S h o r t te rm c o l d s t r e s s i s a l s o acc ompanied by m a ss iv e h e a t p r o d u c t i o n
( t h e r m o g e n e s i s ) v i s i b l e a s s h i v e r i n g (Gonyou e t a l .
1979) and powered
10
by f r e e f a t t y a c i d s (Young I 9 7 5 a ) o b t a i n e d t h r o u g h t h e o x i d a t i o n o f
a d i p o s e t i s s u e ( B l a x t e r and Wainman 1961).
Acute c o l d s t r e s s o c c u r s i f an a n i m a l i s removed from i t s th erm o ­
n e u t r a l zone.
T h i s i s t h e r a n g e of t e m p e r a t u r e s i n which an a n i m a l ' s
heat production i s constant.
F i g u r e I shows t h e t h e r m a l n e u t r a l zone
and t h e r e g i o n s of t h e r m o g e n e s i s a s t e m p e r a t u r e s
drop below o r r i s e
above t h i s l e v e l .
Heat
Production
Cold \
Thermo-'
genesis
Thermo­
neutral
Zone
Cold
Thermal
Environment
F i g u r e I.
Heat p r o d u c t i o n a s r e l a t e d t o t h e t h e r m a l e n v i ro nm en t of
b e e f c a t t l e ( a d a p t e d from Young 1980).
As c o l d e x p o s u r e c o n t i n u e s ( c h r o n i c c o l d s t r e s s ) , r e s p o n s e s t o
c o l d c h a n g e , b u t t h e i n c r e a s e d m e t a b o l i c r a t e c o n t i n u e s ( S l e e 1971,
Young and C h r i s t o p h e r s o n 1974,
Young 1980).
Young and C h r i s t o p h e r s o n
( 1 9 7 4 ) r e p o r t e d a n 8 t o 40 p e r c e n t r i s e i n t h e r m o n e u t r a l m e t a b o l i c
h e a t p r o d u c t i o n d u r i n g p r o lo n g e d c o l d ex p o s u r e . The new l e v e l of h e a t
p r o d u c t i o n depended on t h e av er a ge t e m p e r a t u r e t o which a n i m a l s had
previously
been exposed.
S pecifically,
the average
increase
in
t h e r m o n e u t r a l r e s t i n g h e a t p r o d u c t i o n f o r e a c h 1°C r i s e i n a v e r a g e
t e m p e r a t u r e t o which a n i m a l s had been exp os ed was 0.6 k c a l p e r kg body
w e ig h t'? ^
p e r day.
D uring p ro lo n g ed
cold
exposure
the in c re a se d
11
m etab o lic
rate
acclim atization.
becom es
th e
b asis
for
cold
ad ap tatio n
or
The t h e r m o n e u t r a l z o n e s h i f t s t o i n c l u d e t h e new
l e v e l o f h e a t p r o d u c t i o n a s s e e n i n F i g u r e 2.
Heat
Production
Cold
adapted
Warm
adapted
Tem perature
F i g u r e 2.
Heat p r o d u c t i o n and co l d a d a p t a t i o n i n b e e f c a t t l e
from Young 1980).
(adapted
Each s h i f t i n t h e t h e r m o n e u t r a l zone b r i n g s a new l o w e r c r i t i c a l
tem perature.
critical
Even
W ebster
(1970a) r e p o r t e d
that
the
absolute
low er
t e m p e r a t u r e f o r p r e g n a n t b eef cows r a n g e s from -11 to -23°C.
though
tem peratures
drop
below
-23°C
in
w inter, c a ttle
can u s u a l l y s u r v iv e th e s e p e r io d s w ith a c u te cold re s p o n s e s .
Young
(1975b) s t u d i e d a group of cows a c c l i m a t i z e d t o J a n u a r y t e m p e r a t u r e s
a p p r o a c h i n g -25°C.
When exposed t o -30°C,
metabolic r a t e s increased
up t o 37%, b u t r e c t a l t e m p e r a t u r e s d e c r e a s e d s h o w i n g t h a t t h e cows
w er e n o t m a i n t a i n i n g homeothermy.
A cclim atization
also
involves oth er
m echanism s a s d e fe n s e s
a g a i n s t co ld such as an i n c r e a s e d h e a r t r a t e w hich
increased m etabolic r a te
(W ebster e t a l .
1970).
c o n t r i b u t e s to
R espiratory ra te
d e c r e a s e s t o m i n i m i z e l o s s o f h e a t f r o m w a t e r v a p o r ; Young ( I 9 7 5 a )
reported re sp ira to ry
r a t e s i n cows a s lo w a s 8 t o 11 b r e a t h e s p e r
12
m in u te .
V asoconstriction a t the skin surface continues,
v a s o d ila tio n occurs,
prevent tis s u e
follow ed
by s l o w
constriction,
but p e r i o d i c
in
order
to
damage a t t h e e x t r e m i t i e s (B l a x t e r and Wainman 1961).
H a i r s h e d d i n g i s r e d u c e d , which can l e a d t o a h a i r c o a t t w i c e a s heavy
a s unexposed a n i m a l s (Webster e t a l .
1970).
Cold e x p o s u r e b r i n g s on a
r e l a t i v e l y dehydrated c o n d itio n i n exposed an im als as t h e i r w ater
c o n s um p ti o n d r o p s (Young 1975a).
As c a t t l e
became a d a p t e d t o c o l d e r
tem peratures, m etabolic c a p a b ili ty i n r e s p o n s e to a c u t e co ld s t r e s s
i n c r e a s e d ( S l e e 1971).
These
mechanisms
combine t o i m p l y a g r e a t e r
e n e r g y consumption by a n i m a l s a c c l i m a t e d t o c o l d .
The h e a t c o n s e r v a t i o n a t t e m p t e d d u r i n g a c u t e c o l d s t r e s s i s
a c c o m p a n i e d by a d r o p i n f o o d i n t a k e ( W e b s t e r a n d Young 1 970, S l e e
1971)=.
The g r e a t e r e n e r g y o u t f l o w t h a t f o l l o w s d u r i n g c h r o n i c c o l d
s t r e s s i s a c c o m p a n i e d , by a n i n c r e a s e i n f o o d i n t a k e a b o v e n o r m a l
levels
(Webster and Young 1970, Webster e t a l . 1970, S l e e 1971, B a i l e
and F o r b e s 1974, Ames and Br in k 1977).
The pr o lo n g ed co l d changes t h e
a n i m a l s p h y s i o l o g i c and e n v i r o n m e n t a l c i r c u m s t a n c e s .
In o rd e r to
m a in ta i n a c o n s ta n t energy b alan ce w ith th e se changes, c a t t l e must
in crease
t h e i r food i n t a k e
( B a i l e a n d F o r b e s 1 97 4) .
H ow ev er,
the
i n c r e a s e d h e a t p r o d u c t i o n needed d u r i n g p r o lo n g e d co l d e x p o s u r e w i l l
o c c u r no m a t t e r w h at t h e f o o d i n t a k e l e v e l o f t h e a n i m a l (B l a x t e r and
Wianman 1961, Young 1975b).
t i o n to th e animal,
This shows t h e i m p o r t a n c e o f h e a t p r od u c­
and s u p p o r t s t h e f i n d i n g s t h a t a d i p o s e t i s s u e i s
a l s o us ed t o f u e l h e a t p r o d u c t i o n .
Thus f a r ,
te m p e r a tu r e alone has been d is c u s s e d to i n d i c a t e th e
d e g r e e o f c o l d exp os ur e.
Wind can a g g r a v a t e t h e e f f e c t o f t e m p e r a t u r e
13
w i t h p r o n o u n c e d a d d i t i o n s t o t h e e f f e c t i v e t h e r m a l .en vir onm en t,
cold tem peratures,
wind w i l l
At
i n v o k e h i g h e r h e a t p r o d u c t i o n (Webster
19 7 0 a) a n d a h i g h e r m e t a b o l i c r a t e
(C hristopherson e t al.
19 7 9 ).
I n s l e y and Ames (1972) d e t e r m i n e d t h a t wi nd v e l o c i t e s u n d e r 32 k m/ hr
rem oved an i n s u l a t i n g l a y e r of a i r s u r r o u n d i n g t h e a n i m a l and t r a p p e d
i n t h e h a i r co at . Above, 32 km/hr t h e wi nd a l s o d e s t r o y e d t h e s t r u c t u r e
o f t h e i n s u l a t i n g h a i r c o a t c a u s i n g a second,
accelerated r is e in heat
flow .
Cold e x p o s u r e n o t o n l y i n c r e a s e s an a n i m a l ’s m a i n t a i n e n c e ener gy
requirem ents, i t also in flu e n c e s th e d ig e s 'tiv e system of ru m in a n ts .
S e v e r a l s t u d i e s hav e shown a s i g n i f i c a n t d e c r e a s e i n DMD (dry m a t t e r
d i g e s t i b i l i t y ) d u r i n g p r o l o n g e d c o l d e x p o s u r e ( B l a x t e r a n d Wainman
1961 , Young a n d C h r i s t o p h e r s o n 19 7 4 , Kennedy e t a l . 1 9 7 6 , Ames and
B r in k 1977).
The mechanisms of t h i s d e c r e a s e i n d i g e s t i b i l i t y i n v o l v e
in c re a s e d d i g e s t s flow
t r a c t (Kennedy e t a l .
th r o ug h t h e rumen and l o w e r g a s t r o i n t e s t i n a l
1976,
Kennedy and M i l l i g a n 1978) a s s o c i a t e d w i t h
i n c r e a s e d r u m i n a t i o n t i m e (Gonyou e t a l .
1979) and i n c r e a s e d r e t i c u l a r
c o n t r a c t i o n s ( W es tr a and C h r i s t o p h e r s o n 1976).
The
increased
passage
rate
through
the
reticulorum en
is
p a r t i a l l y c o u n t e r a c t e d by t h r e e r e s p o n s e s : i n c r e a s e d i n t a k e d u r i n g
p r o l o n g e d c o l d e x p o s u r e and t h u s a n i n c r e a s e i n t h e t o t a l am ou nt o f
n u trien ts
p resen ted
for
d ig estio n
( Young
1981,
W estra
and
C h r i s t o p h e r s o n 1976), an i n c r e a s e i n t h e a p p a r e n t d i g e s t i b i l i t y i n t h e
in testin e s
(Kennedy e t
al.
197 6) ,
and an i n c r e a s e
in
m icrobial
e f f i c i e n c y a s s o c i a t e d w i t h t h e d e c r e a s e d t u r n o v e r t i m e (Kennedy e t a l .
1 976 ).
An e f f e c t o f c o l d e x p o s u r e p o s s i b l y r e l a t e d t o c h a n g e s i n
14
d i g e s t i b i l i t y i s a d e c r e a s e i n r u m e n f l u i d v o l u m e (D ege n an d Young
1980, Kennedy e t a l . 1 976) f o l l o w e d by a d e c r e a s e i n t h e v o l u m e o f
in terstitial
f l u i d and p l a s m a (Degen and Young 1980).
Young (1981) and Young and C h r i s t o p h e r s o n ( 1974) have su mmarized
t h e e f f e c t s o f cold. • They found a 16% av er a ge i n c r e a s e i n a n nu al f e e d
needs
caused
asso ciated
in
w ith
equal
proportions
increased
passage
by
rate
(I)
a
reduction
and d e c r e a s e d
in
DMD,
d igestive
e f f i c i e n c y , and ( 2 ) a h i g h e r m a i n t a i n e n c e r e q u i r e m e n t , a s s o c i a t e d w i t h
i n c r e a s e d r e s t i n g m e t a b o l i c r a t e and an i n c r e a s e d en er g y r e q u i r e m e n t .
These
authors
e f f e c t ",
also
discussed
th e need to
a "relativ ely
produce h e a t
minor
but
im portant
during ac u te cold s t r e s s
(i.e.
s t o r m s ) i n o r d e r t o m a i n t a i n homeothermy.
Pregnan cy as i t A f f e c t s D i e t a r y Re qu ir em ent s and I n t a k e
Added to t h e e f f e c t s o f p r o lo n g e d c o l d ex p o su re a r e some im p o r ­
t a n t e f f e c t s of l a t e pregnancy.
cavity i s lim ite d ,
volume,
as the fe tu s
S in c e t h e volum e of t h e a b d o m i n a l '
g r o w s a n d o c c u p i e s mo re o f t h a t
rumen volume d e c r e a s e s (Grahm and W i l l i a m s 1962; F o r b e s 1969,
1970; B in e s 1971;).
Although u t e r u s volume i n c r e a s e s s t e a d i l y ,
F or b es
( 1968) found t h a t rum en volum e d i d n o t d e c r e a s e u n t i l t h e l a s t f i v e
weeks of pregnancy.
I n an e x p e r i m e n t c o n d u c te d w i t h ewes (F o rb es
1969) i t was conc lu ded t h a t t h e volume o f t h e abdominal c a v i t y has an
u p p e r . l i m i t and t h a t th e ex p a n d a b le o r g a n s ' w i t h i n th e c a v i t y must
compete f o r t h a t space.
The t h r e e t i s s u e s most i n c o m p e t i t i o n a r e t h e
u t e r u s , t h e rumen, and d e p o s i t s of ab d o m in al f a t .
A decline in intake
i n th e l a s t weeks o f pregnancy has been a t t r i b u t e d to th e r a p i d l y
15
e x p a n d i n g u t e r u s c a u s i n g a r e s t r i c t i o n on t h e a m o u n t o f v o l u n t a r y
i n t a k e p o s s i b l e (John son e t a l . 1966, Cu r r an e t a l . 1967, F o r be s 1970,
B i n e s 1971).
Pregnancy d i d n o t seem t o a f f e c t t h e volume of d i g e s t a
i n t h e l o w e r i n t e s t i n a l t r a c t (For bes 1969).
C a m p l i n g (1966)
pregnancy.
h a s shown ch a n g e s i n i n t a k e
behavior during
P r e g n a n t cows a t e more s l o w l y and r u m i n a t e d l o n g e r th a n
t h e i r n o n - p r e g n a n t mo no z y go tic t w i n s .
Thi s b e h a v i o r r e s u l t e d i n a 13
p e r c e n t l o w e r hay i n t a k e f o r th e p r e g n a n t cows.
It
has also
been shown t h a t
in creased
passage
rate
is
a
p h y s i o l o g i c a l s i d e e f f e c t o f l a t e p r e g n a n c y (Grahm and W i l l i a m s 1962).
A lthough i n c r e a s e d p a s s a g e r a t e would te n d to o f f s e t t h e d e c re a s e d
i n t a k e caused by s m a l l e r rumen volume,
b o th f a c t o r s would c o n t r i b u t e
t o un de r n u t r i t i o n i n t h e l a s t weeks o f pregnancy.
Forb es (1970) p o s t u l a t e d t h a t a change i n e n d o c r i n e b a l a n c e cou ld
a l s o cause a d e p r e s s i o n i n fo o d i n t a k e .
p r o g e s t e r o n e w a s sh o w n t o d e p r e s s
Estrogen i n t h e
p r e s e n c e of
v o l u n t a r y i n t a k e , and e s t r o g e n
s e c r e t i o n by t h e p l a c e n t a i n c r e a s e s d u r i n g t h e l a s t t h i r d o f pregnancy
(Robin so n 1957 a s c i t e d i n F o rb es 1970).
R o b i n s o n a nd F o r b e s (1 967) s t u d i e d t h e p r o t e i n r e q u i r e m e n t s o f
m a t u r e b r e e d i n g ew es .
A d e c l i n e i n i n t a k e was s e e n a s p r e g n a n c y
advanced;
w as m o r e p r o n o u n c e d on l o w - p r o t e i n d i e t s
the
decline
(5.5 p e r c e n t v s .
H o w e v er ,
the
11 p e r c e n t
efficien cy
pregna nc y advanced.
of
crude
p ro tein in
digested
the e n t i r e
N u tilizatio n
ration).
im proved
as
The i n t a k e of a p p a r e n t l y d i g e s t e d N r e q u i r e d f o r
maximum r e t e n t i o n e f f i c i e n c y d e c r e a s e d from 0.623 g/kgW^'^^/day a t
10-12
weeks p r e g n a n t t o 0.567 g / k g W0,7 3 / d ay a t 18-20 weeks p re g n an t .
16
T he
fetu s
has
undernutrition.
p rio rity
for
am ino
acids
in
co n d itio n s
of
The d e c r e a s e i n e q u i l i b r i u m N r e q u i r e m e n t s s e e n i n
t h i s s t u d y s u g g e s t s some t r a n s f e r o f N from m a i n t a i n c e t o p r o d u c t i o n
d u r i n g pr egn anc y and u n d e r n u t r i t i o n .
B esid es
usin g
N for
feta l
developm ent,
the
anim al
also
e x p e r i e n c e s an i n c r e a s e d e n e r g y r e q u i r e m e n t d u r i n g p r e g n a n c y .
This
h a s been shown w i t h m e a s u r e s o f h e a t l o s s from p r e g n a n t and non­
p r e g n a n t ewes.
During t h e 145 days o f pregnancy,
p r e g n a n t ewes l o s t
39.5 m e a l m o r e h e a t t h a n - n o n - p r e g n a n t e w e s ( B r o c k w a y e t a l .
19 6 3 ).
During pr egn anc y t h e a n i m a l e x p e r i e n c e s g r e a t e r n u t r i t i o n a l n eed s w i t h
a d e c r e a s i n g a b i l i t y t o o b t a i n them.
S u p p l e m e n t a t i o n a s i t A f f e c t s W in te r F or ag e I n t a k e
The most i m p o r t a n t and most v a r i e d s u p p l e m e n t s f o r cows g r a z i n g
w i n t e r r a n g e a r e p r o t e i n and energ y.
As d i s c u s s e d p r e v i o u s l y ,
a r e o f te n l i m i t i n g i n a w in te r range s e t t i n g .
these
A compounding f a c t o r i s
t h e f a c t t h a t e n e r g y n eed s a r e met f i r s t and p r o t e i n w i l l be used f o r
e n e r g y u n t i l i t i s no l o n g e r l i m i t i n g ( C la n to n 1981).
When f e e d i n g a d i e t a r y s u p p l e m e n t t o cows on w i n t e r r a n g e , i t i s
im portant to feed ju s t th a t,
Therefore,
a supplem ent,
and n o t a r e p l a c e m e n t .
th e s u p p l e m e n t ' s e f f e c t s on t h e i n t a k e and d i g e s t i b i l i t y o f
t h e f o r a g e a r e m o s t i m p o r t a n t a n d w i l l be d i s c u s s e d h e r e .
S e v e r a l e x p e r i m e n t s have shown t h a t
p r o te in supplem ent
can
i n c r e a s e t h e i n t a k e of low p r o t e i n f e e d (Cla nto n and Zimmerman 1965,
Cook a n d H a r r i s
1 9 6 8 a,
To pp s 1972,
B r a n i n e a n d G a l y e a n ( 1 985)
C l a n t o n 1981,
Turner
rep o rte d increased passage r a te
1985).
(a n d
17
d e c r e a s e d t u r n o v e r t i m e ) a nd i n c r e a s e d i n t a k e w he n s t e e r s g r a z i n g
m a t u r e b l u e g r a m a r a n g e l a n d w e r e f e d .5 k g o f c o r n /
head /
day
c o m p a r e d t o s t e e r s f e d no s u p p l e m e n t a n d I kg o f c o r n / h e a d / da y .
However,
th is
e f f e c t i s n o t alw ays seen (R itte n h o u se
1 9 6 9 ).
The
i n f l u e n c e s seem t o be dep endent on t h e c o n c e n t r a t i o n o f crude p r o t e i n
i n the forage.
A gen era lly accepted r u l e i s
w ill
i n t a k e w h en p r o t e i n l e v e l s i n f o r a g e a r e b el o w 8%
increase
th a t p r o t e i n supplements
( A l l i s o n 19 8 5 ).
As h a s a l r e a d y been d i s c u s s e d ,
of p assag e i n
pr egn anc y,
the re tic u lo ru m e n ,
cold weather s t i m u l a t e s th e r a t e
rum en volume
during
and l i g n i n and c e l l w a l l c o n s t i t u e n t c o n t e n t s a r e h ig h i n
w i n t e r f o r a g e w h i l e p r o t e i n c o n t e n t i s low.
p article
decreases
G iven t h e s e f a c t o r s ,
s i z e r e d u c t i o n of i n d i g e s t i b l e f i b e r i n t h e rumen would
a p p e a r t o be t h e l i m i t i n g p r o c e s s i n r e m o v i n g m a t e r i a l from t h e rumen
and
allow ing
achieving
fu rth er
particle
ferm entation.
intake
size
(We lc h
reduction
1982).
are
The t w o
r u m i n a t i o n and
methods
of
m icrobial
R u m i n a t i o n i s a p r o c e s s d i r e c t l y c o n t r o l l e d by t h e
a n im a l i n r e s p o n s e t o . t h e f i b e r f r a c t i o n of th e f o r a g e .
The t i m e
s p e n t r u m i n a t i n g h a s shown a s t r o n g p o s i t i v e c o r r e l a t i o n t o t h e - c e l l
w a l l c o n s t i t u e n t c o n t e n t o f f e e d ( W e l c h a n d S m i t h I 9 6 9 ).
M icrobial
f e r m e n t a t i o n r e l i e s on t h e a c t i v i t y and numbers o f rumen m i c r o f l o r a .
Any f a c t o r , i n c l u d i n g a l l t h o s e m e n t i o n e d above, t h a t d e c r e a s e s m i c r o f l o r a a c t i v i t y o r n u m b e r s c a n be e x p e c t e d t o d e c r e a s e DMD ( C r a m p t o n
1952) and,
therefore,
decrease intake.
The p o s i t i v e e f f e c t of p r o t e i n
s u p p l e m e n t a t i o n on d i g e s t i b i l i t y a n d i n t a k e may be due t o a p o s i t i v e '
e f f e c t on m i c r o b i a l
dig estio n
(Cam pling e t a l .
1 962,
Eg an 19 6 5 )^
18
P r o t e i n s u p p l e m e n t a l l o w s t h e o p t i m i z a t i o n of m i c r o b i a l s y n t h e s i s ,
num bers, and a c t i v i t y a s th e a v a i l a b l e n i t r o g e n c o n t e n t of th e d i e t
in c r e a s e s a b o v e ,th a t a v a i l a b l e i n fo rag e alone (A rias e t a l.
1951,
Moir and H a r r i s 1962, Zin n and Owens 1981).
-1
' ,
These c o n c l u s i o n s a r e n o t s u p p o r t e d by r e c e n t s t u d i e s t h a t have
a t t e m p t e d t o show i n more d e t a i l t h e e f f e c t s of p r o t e i n s u p p le m e n t on
N d i g e s t i o n and rumen m i c r o b i a l e f f i c i e n c y .
G o e t s c h and Owens ( a s
c i t e d i n G o e t s c h e t a l . I 984) a n d G o e t s c h e t a l . ( 1 98 4 ) h a v e r e p o r t e d
c o n f l i c t i n g r e s u l t s on t h e im p a c t o f p r o t e i n s u p p le m e n t.
The f i r s t
s t u d y showed im p ro v ed m i c r o b i a l e f f i c i e n c y (g m i c r o b i a l N / kg o r g a n i c
m a t t e r f e r m e n t e d ) when a d i e t c o n t a i n i n g 12 p e r c e n t CP (crude p r o t e i n )
was s u p p l e m e n t e d w i t h soybean or c o t t o n s e e d meal t o a l e v e l p r o v i d i n g
17 p e r c e n t CP.
The s e c o n d s t u d y s h o w e d no s u c h i m p r o v e d m i c r o b i a l
e f f i c i e n c y a s CP l e v e l s w e r e i n c r e a s e d f r o m 9.2 t o I 5.1 p e r c e n t .
addition,
In
b a c t e r i a l numbers and t h e amount o f m i c r o b i a l N p a s s i n g t o
th e duodenum r e m a i n e d t h e same a s CP i n th e d i e t r o s e .
However, rumen
p r o t o z o a numbers and ADF ( a c i d d e t e r g e n t f i b e r ) d i g e s t i o n i n c r e a s e d i n
t h e se cond s t u d y when t h e b a s a l d i e t was s up p le m en te d . Grummer e t a l .
(1984) co n cl u d ed t h a t changes i n rumen ammonia c o n c e n t r a t i o n "do n o t
r e g u l a t e p r o t e i n or dry m a t t e r
degradation
by r u m i n a l m i c r o b e s " .
There r e m a i n s a need f o r c l a r i f i c a t i o n o f t h i s t o p i c .
There i s s t r o n g
e v i d e n c e s h o w i n g i n c r e a s e d i n t a k e o f l o w q u a l i t y f o r a g e when s m a l l
amounts o f p r o t e i n su p p le m e n t a r e p r o v id e d .
S t u d i e s sh owing e v i d en ce
t o t h e c o n t r a r y may ,have f e d d i e t s d i f f e r i n g t o s u c h a n e x t e n t t h a t
'
I
r e s u l t s s h o u l d h o t be compared.
1-9
W h i l e s u p p l e m e n t s may i n c r e a s e t h e d i g e s t i b l e p r o t e i n r e c e i v e d
from ra n g e f o r a g e ,
Cook a n d H a r r i s (1 96 8a ) sh o we d t h a t t h e r e i s a n
a c c o m p a n y i n g d e c r e a s e i n t h e d i g e s t i b i l i t y o f c e l l u l o s e and g r o s s
en erg y.
The cows r e c e i v e d l e s s m e t a b o l i z a b l e ener gy when r a n g e f o r a g e
was s u p p le m en te d.
A p o r t i o n o f t h e p r o t e i n i n any f e e d s t u f f i s u n a v a i l a b l e i n t h e
r u m e n , an d b y p a s s e s o r e s c a p e s t o t h e l o w e r g a s t r o i n t e s t i n a l t r a c t .
The amount o f bypass o r es ca p e p r o t e i n v a r i e s n o t o n l y b et we en f e e d s ,
b u t a l s o w i t h i n f e e d s due t o f e e d p r o c e s s i n g and "a n im al , d i e t a r y , and
m i c r o b i a l v a r i a b l e s " (NEC 19 8 4 ).
The NEC ( I 984) h a s s u g g e s t e d t h r e e
c a t e g o r i s e s o f f e e d s t u f f s based on t h e i r p e r c e n t a g e o f bypas s p r o t e i n :
( I ) low b y p a s s ( l e s s t h a n 40 p e r c e n t ) ,
i n c l u d i n g s o y b e a n m e a l and
peanut
to
m eal;
( 2 ) medium
bypass
(40
60
percent),
including
c o t t o n s e e d m e a l , d e h y d r a t e d a l f a l f a m e a l , c o r n g r a i n , and b r e w e r s
d r i e d g r a i n s ; and (3) h i g h bypass ( g r e a t e r th a n 60 p e r c e n t ) , i n c l u d i n g
me at me al,
c o r n g l u t e n me al, blood m e al , f e a t h e r me al, and f i s h meal.
The s u p p l e m e n t s u se d i n t h i s s t u d y had a so ybean meal base.
H arris
( 196 8 a) u s e d t h e
n y l o n b ag t e c h n i q u e
to
Cook and
determ ine th a t a
soybean meal s u p p le m e n t c o n t a i n i n g 48.2 p e r c e n t t o t a l p r o t e i n was 83.4
percent
d i g e s t i b l e i n t h e rumen.
Hume (1 974) r e p o r t e d a s i m i l a r
a p p a r e n t DMD f o r s o y b e a n m e a l o f 83.1 p e r c e n t .
bypass p r o te in ,
In h i s review
of
C h a l u p a ( 197 5) r e p o r t e d t h a t 40 t o 59 p e r c e n t o f
so ybean meal p r o t e i n w i l l bypas s or e s c a p e t h e rumen,
and t h e r e f o r e ,
w i l l be u n a v a i l a b l e t o rumen mi cr o b es .
The
benefits
of
bypass
protein
resu lt
from
a increase
in.
e s s e n t i a l amino a c i d s a v a i l a b l e t o th e a n i m a l i n t h e s m a l l i n t e s t i n e
20
and g r e a t e r t r u e d i g e s t i b i l i t y o f q u a l i t y p r o t e i n s c o m p a r e d t o t h e
digestibility
However,
of crude p r o t e i n from rumen m i c r o b e s
as p r o t e i n
b yp as s o r e s ca p e i n c r e a s e s ,
(Van S o e s t 1983).
t h e o p t i m i z a t i o n of
m i c r o b i a l s y n t h e s i s , n u m b e rs , and a c t i v i t y i s n o t p o s s i b l e , and t h e
p o s i t i v e fo ra g e in ta k e e f f e c t seen w ith p r o te i n supplem ent i s l e s s
likely.
E x p e r i m e n t s w her e s u p p l e m e n t a l en erg y ( c a r b o h y d r a t e ) was f e d have
g e n e r a l l y shown a d e c r e a s e i n f o r a g e i n t a k e due t o a s u b s t i t u t i o n of
t h e s u p p l e m e n t f o r f o r a g e ( H o l d e r I 9 6 2 , C a m p l i n g a n d Mu rdoch 1 966,
E llio tt
1 96?,
R ittenhouse e t
al.
1 970,
B e l l o w s a n d Thomas
M e r r i l l and K l o p h e n s t e i n 1984, A l l i s o n 1985).
been shown to
decrease
the
d ig estio n
1 976,
Energy s u p p le m e n ts have
of
cellu lo se
and o th e r
c a r b o h y d r a t e s (Cook and H a r r i s 1968a ) „
S t u d i e s w here both p r o t e i n and e n e r g y a r e f e d a r e i n c o n c l u s i v e .
C la nt on (1981) f e d c o m b i n a t i o n s o f p r o t e i n and en er g y t o cows, but saw
no s i g n i f i c a n t d i f f e r e n c e i n dry m a t t e r i n t a k e or d i g e s t i b i l i t y when
averages
for
supplem ented
i
groups
were
compared
to
the
control
i
( un s up p le m en te d ) group.
R al e ig h and W a l la c e (1963) found an i n c r e a s e
i n f o r a g e i n t a k e whe n l o w l e v e l s o f p r o t e i n w e r e f e d r e g a r d l e s s o f
energy le v e l.
When h i g h l e v e l s o f p r o t e i n w e r e f e d ,
d ecre ase d , ag ain , r e g a r d l e s s of energy le v e l.
forage in tak e
T u r n e r (1 985) f o u n d
i n c r e a s e d i n t a k e o f r a n g e f o r a g e w i t h 1.8 k g / d a y o f a 1 5 % p r o t e i n
supplem ent.
B u t w hen h a l f t h a t same s u p p l e m e n t a n d 0.9 k g / d a y o f a
30% p r o t e i n s u p p le m e n t w ere f e d ,
was seen.
no i n c r e a s e i n i n t a k e o v er c o n t r o l s
21
K a r t c h n e r (1981) s u p p l i e d a p r o t e i n and an en er g y su pp le m en t t o
g r o u p s of cows d u r i n g two s u c c e s s i v e w i n t e r s .
The f i r s t w i n t e r was
m i l d w i t h r e a d i l y a v a i l a b l e f o r a g e , no i n t a k e a d v a n t a g e w a s g a i n e d
fr om e i t h e r s u p p le m e n t.
The second w i n t e r was more s e v e r e and i n t a k e
and DMD w ere enhanced by p r o t e i n s u p p l e m e n t , bu t d e p r e s s e d w i t h energy
su p p le m en t.
The e f f e c t o f s u p p l e m e n t c a n a l s o be a f f e c t e d by t h e t i m i n g o f
supplem entation.
Adams
(1984b)
and
K artchner
and
Adams
(1982)
r e p o r t e d t h a t cows f e d e v e r y day g a i n e d w e i g h t a n d c o n d i t i o n w h i l e
t h o s e f e d e v e r y o t h e r day g a i n e d l e s s w e i g h t a n d l o s t
These f i n d i n g s
w ere a t t r i b u t e d
to
the
condition.
e f f e c t s w i t h i n t h e rumen.
A l t e r n a t e day f e e d i n g b r o u g h t r e d u c e d ph and i n c r e a s e d VFA c o n c e n t r a ­
tio n s.
Lower r u m e n ph b r i n g s a b o u t r e d u c e d f i b e r d i g e s t i o n w h i c h
c o u l d a c c o u n t f o r t h e l o w e r w e i g h t g ai n .
Adams ( 1 9 8 4 a , b) a l s o s t u d i e d t h e e f f e c t o f t h e t i m e o f day o f
supplement feeding.
S te e rs fe d i n the e a r l y afternoon spent l e s s time
g r a z i n g , but consumed more f o r a g e , and had a h i g h e r a v e r a g e d a i l y g a i n
t h a n s t e e r s f e d i n t h e morning.
supplem ent i n
The a u t h o r
postu lated th a t feeding
th e morning d is r u p te d normal g r a z in g a c t i v i t y
and
a f f e c t e d b o th b e h a v i o r and pe r f or m a n ce .
Many
stu d ies
have
d ealt
w ith
th e
c u r r e n t and s u b s e q u e n t
p e r f o r m a n c e o f co w s r e c e i v i n g w i n t e r s u p p l e m e n t .
Cows h a v e l o s t
s u b s t a n t i a l a m o u n t s o f body f a t o v e r t h e w i n t e r w i t h o u t a d v e r s e l y
a f f e c t i n g t h e i r s u b s e q u e n t p e r f o r m a n c e or th e p e r f o r m a n c e of t h e i r
c a l v e s (Thompson e t a l .
1983,
Turner 1985).
But s u p p le m en t l e v e l has
b e e n d i r e c t l y r e l a t e d t o a cow’s w i n t e r w e i g h t l o s s a n d i n v e r s e l y
22
r e l a t e d t o h e r co ns um pt ion o f s p r i n g , summer f o r a g e and summer w e i g h t
g a i n ( R i g h t 1 966, J o r d a n e t a l . 1 968, L u s b y e t a l . I 976, Thompson e t
a l . 1 9 8 3 , T u r n e r I 985 ).
Cows r e c e i v i n g l i t t l e
o r no w i n t e r s u p p l e m e n t h a v e sh own a
reduced reproductive cap a b ility .
S e v e r a l s t u d i e s have shown a d el a y e d
r e t u r n t o e s t e r u s i f p r e - c a l v i n g n u t r i t i o n i s low ( W i ltb a n k e t a l .
I 962, J o r d a n e t a l . I 968, Dunn e t a l . I 9 6 9 , W h i t m a n 1 975, B e l l o w s a n d
Short
1 978).
calving,
For
cow s i n
good,
m oderate,
and t h i n
condition a t
t h e i r l i k e l i h o o d of e s t r u s 60 days p o s t p a r t u m was 0.91, 0.61,
a n d 0.46 r e s p e c t i v e l y ( W h i t m a n 1 9 7 5 ) .
C o n c e p t i o n r a t e may a l s o be
l o w e r f o r cows on a low p la n e o f w i n t e r n u t r i t i o n ( H a r r i s e t a l . 1956,
W i l t b a n k e t a l . 1 962 , C l a n t o n an d Z i m m e r m a n 1 9 6 5) .
When cows on a
h ig h p la n e of n u t r i t i o n b e fo re and a f t e r c a l v i n g w ere bred,
percent
did not conceive,
only 5
c o m p a r e d t o 33 p e r c e n t o f t h e cows n o t
c o n c e i v i n g h a v i n g b e e n on a l o w p l a n e o f n u t r i t i o n ( W i l t b a n k e t a l .
1962) .
I t i s i m p o r t a n t t o r e m e m b e r t h a t a cow c a n o b t a i n t h e e x c e s s
e n e r g y needed d u r i n g t h e w i n t e r th r o u g h e x t r a f e e d o r m o b i l i z a t i o n of
fat.
I f cows a r e n o t r e c e i v i n g e x t r a p r o t e i n a n d e n e r g y p r i o r t o
calving,
t h e y w i l l l i k e l y be l o s i n g w e i g h t a s t h e y u s e body t i s s u e
reserves.
The f e r t i l i t y o f a cow 70 t o 90 d ay s p o s t p a r t u m i s d i r e c t l y
r e l a t e d t o t h e amount of body en er g y r e s e r v e s she ha s (Whitman 1975).
Tho mp son e t a l .
( 1983) d i s c u s s e d t h e t o t a l e n e r g y r e q u i r e m e n t f o r
t h r e e me thods o f w i n t e r i n g c a t t l e :
I) f a l l f a t t e n i n g and l i t t l e w i n t e r
s u p p l e m e n t , 2 ) k e e p i n g co w s i n a t h i n c o n d i t i o n y e a r r o u n d , and 3 )
k e e p i n g cows f a t y e a r round.
Al l cows were k e p t a t s i m i l a r p r o d u c t i o n
23
lev els.
energy,
Covzs t h a t w e r e f a t y e a r r o u n d r e q u i r e d t h e l e a s t t o t a l
and f a l l
fa tte n in g req u ired
t h e most.
The
body e n e r g y
r e s e r v e s o f t h e f a t oows a l l o w e d them t o o v e r w i n t e r w i t h l e s s s u p p l e ­
ment t h a n t h e t h i n cows w h i l e s t i l l r e m a i n i n g p r o d u c t i v e .
A l i m i t e d amount o f p r e - c a l v i n g w e i g h t l o s s i s n o t d e t r i m e n t a l .
Jones e t al.
( 19 79 ) f o u n d t h a t
cows c a n l o s e
up t o 60 kg (+3 6. 2)
w i t h o u t a f f e c t i n g p r e - weaning d a i l y g a i n o r weaning w e i g h t .
Weight
l o s s be y o n d t h i s l e v e l h a s b e e n s h o w n t o l o w e r c a l f b i r t h w e i g h t s ,
c a l f gain,
c a l f weanin g w e i g h t ,
and t h e number of c a l v e s weaned (Black
e t a l . 1 938, S p e t h e t a l . 1 963» C l a n t o n a n d Zimmerman. 1 9 6 5 , R i g h t
19 6 6 ,
H i r o n a k a a n d P e t e r s 1969 ,
1979 , B e l l i d o e t a l . 1981).
Corah e t a l .
19 7 5 ,
R ussell et al.
.
I n t a k e B eh av io r
B e h a v io r i s an i m p o r t a n t ,
tion.
u n d e r l y i n g f e a t u r e o f a n i m a l p r odu c­
I t i s i m p o r t a n t - t o produce b e e f e f f i c i e n t l y ;
therefore,
i t is
i m p o r t a n t t o u n d e r s t a n d b e e f c a t t l e b e h a v i o r ( S t r i c k l i n an d K a u t z Scanavy 1984).
But t h e r e s u l t s of b e h a v i o r s t u d i e s a r e o f t e n v a r i b l e
an d d i f f i c u l t
to i n t e r p r e t .
(H a n c o c k 1953,
cattle
(H a n c o c k
V ariation
S t o b b s 1970) due t o
1950
as
cited
in
among
anim als i s
high
the in h e re n t in d i v id u a l ity
Hancock
1953).
The f a c t
of
th at
o b s e r v e r s have a te n d e n c y t o av o id i n c l e m e n t w e a t h e r and d a r k n e s s adds
i n c o n s i s t e n c i e s w i t h i n an d b e t w e e n b e h a v i o r s t u d i e s
1970).
When s t u d y i n g i n t a k e b e h a v i o r ,
.
(Gary e t a l .
.
animal i n d i v i d u a l i t y i s expressed
t o th e g r e a t e s t e x t e n t a t n i g h t w h i l e d a y t im e g r a z i n g i s more l i k e l y
24
to be a group a c t i v i t y ( B a i l e and F o rb e s 1974, S t r i c k l i n e t a l . 1976).
Many s t u d i e s h a v e i d e n t i f i e d t h e h o u r s j u s t a f t e r s u n r i s e an d a t
s u n s e t a s t h e m o s t a c t i v e g r a z i n g p e r i o d s ( S t o b b s 1 9 7 0 , A r n o ld an d
D u d z i n s k i I 978, Bueno a n d B u c k e b u s c h 1 979, R o a th a n d K r u e g e r 1982,
S t r i c k l i n a n d K a u t z - S c a n a v y 1 9 8 4 ).
c o n s is te n t g ra z in g a c t iv it y
around
m i d n ig h t (S to b b s
S tu d ie s have a ls o
d u rin g th e
1970,
sh o w n l e s s
day a n d a t n i g h t ,
S tric k lin
e t a l.
D u d z in s k i 1978, S t r i c k l i n and K au tz-S can av y 1984).
1976,
u su a lly
A r n o ld and
Gary e t a l .
(1970)
r e p o r t e d t h a t 17 p e r c e n t o f b e e f c a t t l e g r a z i n g o c c u r ed a t n i g h t w h i l e
83 p e r c e n t o c c u re d d u r i n g d a y l i g h t .
G iv e n t h e
su n se t,
b a sic
p a tte rn
of d a y lig h t g ra z in g a t
su n rise
and
w e a th e r and tim e o f y e a r have been shown t o i n f l u e n c e g r a z i n g
p a t t e r n s (A rnold and D u d z in sk i 1978, Ruckebusch and Bueno 1978, Low e t
al.
1981,
Roath and K rueger 1982).
L ength o f d a y l i g h t h a s been shown
t o a f f e c t t h e t i m e o f day w hen g r a z i n g b e g i n s a n d e n d s ; a s d a y s g e t
s h o r t e r more d a y l i g h t h o u r s w ere s p e n t g r a z i n g ( T a y l e r 1951 a s c i t e d
i n Hancock 1953, A rnold and D u d z in sk i 1978, Bueno and Ruckebusch 1979,
W ils o n and F ly n n 1979,
Low e t a l . 1981).
However, d a y le n g th does n o t
d e t e r m i n e t h e t o t a l , am o u n t o f t i m e s p e n t g r a z i n g e a c h d a y ;
cow s
co m p en sa te f o r s h o r t d a y l i g h t h o u r s i n w i n t e r by g r a z i n g more a t n i g h t
(S tric k lin e t al.
1976, W ilson and F ly n n 1979).
A lth o u g h t e m p e r a t u r e h a s n o t b e e n show n t o i n f l u e n c e w hen a
g r a z i n g a c t i v i t y o c c u r s (A rnold and D u d z in sk i 1978,
Roath and K rueger
I 9 8 2 ), i t d o e s a f f e c t t h e a m o u n t o f d a i l y g r a z i n g t i m e .
Cows s p e n d
l e s s t i m e g r a z i n g on c o ld days th a n on warm days ( S m o liak and P e t e r s
1 955,
M a le c h e k a n d S m i t h I 976, Adams 1 9 8 4 a ).
T ab le 3
sh o w s t h e
25
e x te n t
to
w h ic h
g ra z in g
tim e
c a n be e x p e c t e d
t e m p e r a t u r e f a l l s o r w ind v e l o c i t y r i s e s .
to
d ecrease
w hen
This d e c r e a s e d g r a z i n g tim e
on c o ld days h a s been a s s o c i a t e d w i t h d e c r e a s e d en e rg y e x p e n d i t u r e i n
o r d e r t o c u t m a i n t a i n e n c e en e rg y r e q u i r e m e n t s . ' R i t te n h o u s e and S e n f t
(1982) showed t h a t g r a z i n g t i m e d e c r e a s e s w i t h any d e v i a t i o n from th e
th e r m a l n e u t r a l zo n e t o w h ich c a t t l e a r e a c c l i m a t e d .
been shown t o a f f e c t
g razin g a c t i v i t i e s
b u t m o s tl y i n warm o r t r o p i c a l s e t t i n g s .
g ra z in g tim e
H u m id ity h a s
(A rnold and D u d z in sk i 1978),
Adams (1984a) h a s shown t h a t
d e c r e a s e s a s w in d v e l o c i t y i n c r e a s e s .
T a b l e 4 sh o w s
s i g n i f i c a n t c o r r e l a t i o n c o e f f i c i e n t s b etw ee n v a r i o u s a n im a l a c t i v i t i e s
and t h r e e w e a th e r f a c t o r s .
T ab le 3 .
P r e d i c t e d g r a z i n g tim e o f cows a t v a r i o u s
wind v e l o c i t i e s (from Adams 1984a).
Mimimum d a i l y
a i r t e m p e r a t u r e °F
Average d a i l y wind v e l o c i t y (MPH)
O
5
10
15
30
9.1
8.8
8 .4
8.0
15
8.1
7 .8
7 .4
7 .0
0
7.1
6 .7
6 .4
6 .0
-15
6.0
5.6
5.3
4 .9
-30
5 .0 -
4.6
4.3
3 .9
D ra stic
b e h a v io r.
t e m p e r a t u r e s and
changes i n w e a th e r
Bueno and
d iso rg a n iz a tio n
of
th e
b rin g d r a s ti c
R ucke bus ch
(1 9 7 9 ) r e p o r t e d
d a y lig h t r a t i o
ex tre m e changes i n w e a th e r.
ch an g es i n an im al
a " c o m p le te
of g ra z in g " d u rin g q u ic k ,
S t r i c k l i n e t a l . (1 976) r e p o r t e d t h a t
26
c a t t l e d id n o t g r a z e a t a l l d u r in g a th u n d e r s to r m ; th e y t u r n e d t h e i r
b ack s t o t h e w ind and s to o d o r w alk ed w i t h t h e wind.
F orage a v a i l a b i l i t y
f o r a g e becomes s c a r c e ,
h as been shown t o a f f e c t g r a z i n g ti m e s .
As
th e number o f d a i l y g r a z i n g h o u r s i n c r e a s e s a s
a n i m a l s t r y to o b t a i n a c o n s t a n t i n t a k e l e v e l (A lld e n and W h i tta k e r
1970, H av stad e t a l . 1983, L a th ro p e t a l . 1985).
T ab le 4 .
S i g n i f i c a n t c o r r e l a t i o n c o e f f i c i e n t s betw een c a t t l e a c t i v i ­
t i e s and w e a th e r p a r a m e te r s ( a d a p te d from Malechek and Smith
1 9 7 5 ).
A c tiv itie s
D is ta n c e
T r a v e le d
A ir Temp
Baro P re s
change
Wind Speed
G ra z in g
ns
ns
.65
.56
VO
O
Weather
F acto rs
ns
Time s p e n t
R um inating
S ta n d i n g
ns
.63
ns
. 6 8
.70
ns'
ns - n o n s i g n i f i c a n t c o r r e l a t i o n c o e f f i c i e n t s
D a ily t r a v e l by c a t t l e h a s shown a c l o s e c o r r e l a t i o n t o th e tim e
spent
g razin g ,
w ith
in itia tio n
of
tra v e l
o ccu rin g
alo n g
w ith
i n i t i a t i o n o f g r a z i n g a t s u n r i s e a n d s u n s e t ( R u c k e b u s c h a n d Bueno
1978).
The t i m e s p e n t w a lk in g and t h e d i s t a n c e t r a v e l e d p e r day a r e
a ffe c te d
by
w e a th e r
a v a ila b ility ,
and
(esp.
w a te r
Ruckebusch and Bueno 1978).
as re p o rte d
w in d ),
fo rag e
lo c a tio n
a v a ila b ility ,
sh e lte r
( A r n o l d a n d D udzi n s k i . 1978,
The r a n g e o f d i s t a n c e s t r a v e l e d by c a t t l e
i n th e l i t e r a t u r e
( A r n o l d a n d D u d z i n s k i 1 9 7 8 ).
is q u ite
broad,
1.3 t o
12.6 k m /d a y
Some s p e c i f i c e x a m p l e s i n c l u d e :
M o n ta n a sum m er m o u n t a i n r a n g e
c a ttle
tra v e le d
On
3.7 t o 5.7 k m /d a y
27
(L ath ro p e t a l .
tra v e le d
19 8 5 ).
On o p e n r a n g e i n c e n t r a l A u s t r a l i a c a t t l e
9.3 k m / d a y (S.D.=2„6) (Low e t
al.
1981).
Texas r a n g e l a n d w alk ed 5.3 km/day (Hancock 1953).
B eef
c a ttle
on
28
METHODS AND MATERIALS
S tudy S i t e D e s c r i p t i o n
The S t u d y w as c o n d u c t e d i n a 324 h e c t a r e p a s t u r e l o c a t e d on Red
B l u f f R e s e a r c h R anch o p e r a t e d by t h e D e p a r t m e n t o f A n im a l a n d Range
S c i e n c e s , M o n ta n a S t a t e U n i v e r s i t y ,
fo o th ills
of
th e
M a d is o n R ange i n
in c lu d e d
in
th e
le g a l
I 8, T .3S ., R.1 E.
The r a n c h i s i n t h e n o r t h w e s t
so u th w e st
d e sc rip tio n
of
th e
M o n ta n a ,
s tu d y
S e c tio n s
p a stu re
are
P a s t u r e e l e v a t i o n s r a n g e f r o m 1 ,400 t o 1 ,9 0 0 m e t e r s
( 4 ,0 0 0 t o 6 ,2 0 0 f e e t ) w i t h l o n g , s l i g h t t o m o d e r a t e s l o p e s an d a r e a s
1
i
o f s t e e p s l o p e s and r o c k o u tc r o p s . Annual p r e c i p i t a t i o n a v e r a g e s from
350 to 406 mm (14 t o 16 i n c h e s ) ( USDA-SCS 1 976).
A 1980 S o i l C o n s e r v a t i o n S e r v i c e s u r v e y o f t h e r a n c h d e s c r i b e d
t h e p a s t u r e a s a s i l t y r a n g e s i t e i n good c o n d i t i o n w i t h v e g e t a t i o n
composed o f 6 5 p e r c e n t g r a s s e s and 35 p e r c e n t f o r b s and weedy s p e c i e s .
Dominant g r a s s e s i n c l u d e bluebunch w h e a t g r a s s ,
fescue,
and b a s in w ild r y e .
n e e d l e a n d t h r e a d , Idaho
O th e r m a jo r f o r a g e s p e c i e s l i s t e d
by
M ueggler and S t e w a r t (1980) and Payne (1 973) in c l u d e p r a i r i e J u n e g r a s s
( K o e l e r i a o v r a m i d a ta (Lam.) Beav,), t h r e a d l e a f s e d g e ( C a r e x f i l i f o l i a
N u tt.), green n e e d le g ra ss
(S tio a v ir id u la
( Bromus m a r g i n a tu s P i p e r (H itc h c .) ) ,
T rin .),
m o u n t a i n brom e
Kentucky blu e g r a s s (Poa o r a t e n s i s
L .) , w e s t e r n y a r r o w ( A c h i l l e a m i l l e f o l i u m L .), and f r i n g e d s a g e w o r t
( A r t e m i s i a f r i g i d a W illd .) .
S h allo w s i t e s s u r r o u n d i n g r o c k o u t c r o p s
i n t h e p a s t u r e c o n t a i n po n d ero sa p in e (P in u s p o n d e ro sa D ougl.), l i m b e r
p i n e ( P i n u s f l e x u l i s J a m e s ) , a n d Rocky M o u n t a i n j u n i p e r ( J u n i o e r u s
s c o D u lo r u m S a r g.)
A Red B l u f f Ranch p l a n t s p e c i e s l i s t c o m p i l e d by
P a t P la n t e n b u r g can be fo u n d i n T u rn e r ( 1 9 8 5 ).
29
Payne (1973),
i n r e v i e w i n g w e s t e r n M ontana's m a jo r r a n g e s i t e s ,
s t a t e d t h a t f o o t h i l l r a n g e l a n d d o m i n a t e d by b l u e b u n c h w h e a t g r a s s i s
one
of
th e
m ost
common f o r a g e
ty p e s in
th a t p a rt of
th e s t a t e .
E s t i m a t e d c a r r y i n g c a p a c i t y f o r t h i s f o r a g e ty p e was t h r e e a c r e s p e r
AUM (a n im a l u n i t month).
G ra z in g Management
I n 1984,
48 cows w e re p la c e d i n t h e s tu d y p a s t u r e on December 20
a n d r e m o v e d M arch 2. S t o c k i n g d e n s i t y w a s 0.15 AU ( a n i m a l u n i t s ) p e r
• h e c t a r e (0 .0 6 A U / a c r e ) .
The s t o c k i n g r a t e i n 1984 w as 2 .7 8 h e c t a r e s
p e r AUM (7 a c r e s / AUM).
I n 1 9 8 5 , 6 0 cow s w e r e i n t h e p a s t u r e f r o m
D e c e m b e r 14 t o M arch I .
( 0 .0 7 AU/a c r e ) .
S t o c k i n g d e n s i t y w as 0 .1 9 AU p e r h e c t a r e
The s t o c k i n g r a t e w a s 2.08 h e c t a r e s p e r AUM (5.6
acres/A U M ).
O b s e r v a t i o n s o f g r a z i n g d i s t r i b u t i o n w e r e made e a c h w i n t e r ;
how ever,
g r a z i n g d i s t r u b u t i o n was n o t q u a n t i f i e d .
was e s t i m a t e d w i t h a u t i l i z a t i o n gauge
(U.
S.
F orage u t i l i z a t i o n
F o re st S erv ice ).
g a u g e w as d e v e l o p e d u s i n g p l a n t h e i g h t / w e i g h t r a t i o s
g r a s s e s and s e d g e s .
The
o f m a jo r
M easurem ents i n c l u d e d u n g ra z e d and g ra z e d p l a n t
h e i g h t a v e r a g e s o f b lu e b u n ch w h e a t g r a s s o r n e e d l e a n d t h r e a d , and number
o f g r a z e d p l a n t s oh s i x s t e p t r a n s e c t s .
T ra n s e c ts w ere d i s t r i b u t e d
th r o u g h o u t th e p a s t u r e .
I n t a k e Measurment
The e x p e r i m e n t a l cows w ere ra n d o m ly s e l e c t e d from t h e Red B l u f f
R e s e a r c h Ranch h e r d b a s e d on a g e , e x p e c t e d c a l v i n g d a t e s , • and c a l f
sire s.
Herd s i z e was chosen based on t h e q u a n t i t y o f f o r a g e a v a i l a b l e
30
i n t h e s tu d y p a s t u r e ,
se le c tio n c r ite r ia .
and t h e number o f cows on t h e r a n c h t h a t f i t t h e
The cows w ere 3 to 7 y e a r s of age.
The cows w ere
a r t i f i c i a l l y in s e m in a te d th e p re v io u s June u sin g angus or h e re fo rd
semen.
C a lv in g was s c h e d u le d to s t a r t March 4 e a c h y e a r ;
S u p p l e m e n t w a s f e d i n d i v i d u a l l y on a l t e r n a t e d a y s i n t h e e a r l y
a fte rn o o n .
I n 1984, cow s w e r e f e d t h e sam e s u p p l e m e n t : 0.9 kg / day
o f a soybean meal su p p le m e n t p r o v i d i n g 250 g CF (cru d e p r o t e i n ) / day.
I n 1985 t h e cow s w e r e s p l i t i n t o f i v e t r e a t m e n t g r o u p s .
Cow a g e
g r o u p s , e x p e c t e d c a l v i n g d a t e s , and c a l f s i r e s w e r e d i s t r i b u t e d a s
e v e n ly a s p o s s i b l e th ro u g h a l l t r e a t m e n t s .
The t r e a t m e n t s ,
and t h e i r
I n t e r n a t i o n a l Feed Numbers (IFN#) w ere a s f o l l o w s :
TRT I - Forage o n ly (CON)
TRT 2 - F orage p lu s so y b ean m eal (SBM, IFN# 5-04-600)
TRT 3 - F orage p l u s soybean m eal and a n im a l f a t (FAT,
IFN# 4-00-409)
TRT 4 - F orage p l u s so y b ean m eal and b lood meal (SM,
IFN# 5 -0 0 -3 8 0 )
TRT 5 - F o r a g e p l u s s o y b e a n m e a l and c o r n g l u t e n meal(CGM,
IFN# 5 -2 8 -2 4 1 )
Blood m eal and c o rn g l u t e n meal w ere f e d a s s o u r c e s o f b y p a s s p r o t e i n ,
fro m a n a n im a l and p l a n t s o u r c e r e s p e c t i v e l y .
Animal f a t was f e d a s a
s o u r c e o f b y p ass en e rg y i n o r d e r to d e t e r m in e i f any e f f e c t s e e n w i t h
b y p ass p r o t e i n was due t o 1e x t r a e n e r g y o r e x t r a p r o t e i n .
A d e ta ile d
d e s c r i p t i o n o f t h e s u p p le m e n ts f e d i n 1985 i s shown i n T a b le 5.
C h r o m ic o x i d e w as u s e d a s a n e x t e r n a l m a r k e r t o e s t i m a t e f e c a l
o u t p u t ( R a le ig h e t a l .
sm all
1980).
am ount of ground
corn;
Chromic o x id e powder was m ixed w i t h a
th is
p r e m i x w as t h e n a d d e d t o
th e
31
T ab le 5 .
Supplem ent c o m p o s itio n f o r w i n t e r 1985 a t Red B l u f f R esearch
Ranch, N o r r i s , Montana (Miner e t a l . 1986).
TRT
I
Supplem ent
C o n stitu e n ts
g fed
2
SBM
570
250
430
50
200
3
FAT
SBM
210
51SL
0
252.
250
410
430
840
0
52.
50
0
2m
200
370
100
100
50
52.
200
40
162.
200
g TDN
Bypass (g)
780
290
60
SSL
0.
T o ta l
450
140
Ii
606
400
470
190
10
2.
■ 200
T o tal
230
4B0
680
200
222.
400
340
IM
480
160
M
200
BM
SBM
5
g CP
T o ta l
CGM
SBM
Urea
4
P ro te in A v a ila b ility
Rumen (g)
1P o ta s s iu m c h l o r i d e , d e calciu m p h o s p h a te , V itam in A, and a m o la s s e s
b o o s t e r w ere added t o a l l s u p p le m e n ts .
s u p p le m e n ts .
i n 1985.
The s u p p le m e n t was p e l l e t e d i n 1984,
F e c a l g ra b s a m p le s from t h e e n t i r e h e rd w e re t a k e n
i n 1984 and b iw e e k ly i n 1985.
also
b u t was f e d l o o s e
made on
I n 1985, t o t a l f e c a l
f o u r cows from each
group u s i n g
c o lle c tio n s
w ere
f e c a l bags and
u rin e
/ f e c e s s e p e r a t o r f l a p s (K a r tc h n e r and R it te n h o u s e 1979).
w ere made t w i c e d u r i n g t h e s tu d y p e r io d .
h o u rs f o r 4 c o n s e c u tiv e days.
m ixed, and sam pled.
w eekly
C o lle c tio n s
Bags w ere changed e v e ry 24
E ach d a y 's c o l l e c t i o n w a s w e i g h e d ,
Sam ples w ere f r o z e n f o r l a t e r a n a l y s i s .
A f t e r th a w in g , dry m a t t e r and o r g a n i c m a t t e r w ere d e te r m in e d f o r
e ac h f e c a l sam ple f o l l o w i n g AOAC (1975) p r o c e d u r e s .
th e s am p le was ground th ro u g h a 2mm s c r e e n .
tio n
in
The r e m a in d e r o f
Chromic o x id e c o n c e n tr a ­
e a c h -sam p le w a s d e t e r m i n e d u s i n g t h e
s p e c t r o p h o t o m e t r y te c h n i q u e ( W il li a m s e t a l . 1962).
a to m ic a b s o r p tio n
F e c a l dry m a t t e r
32
o u t p u t p e r day was e s t i m a t e d from g r a b s a m p le s based on t h e f o l l o w i n g
eq u atio n :
g chrom ic o x id e f e d / day .
g f e c a l o u t p u t / day = ---------------------------------------------------- % ioo
$ chrom ic o x id e i n dry f e c a l sam ple
Two a d j u s t m e n t s w ere made t o t h i s o r i g i n a l e s t i m a t e from g r a b sam p les.
C h r o m ic o x i d e r e c o v e r y w as c a l c u l a t e d a n d t h e q u a n t i t y o f c h r o m i c
o x id e fe d
per
day a d j u s t e d
a c c o rd in g ly .
A lso ,
fecal
o u tp u t
m e a su re m e n ts from t o t a l f e c a l c o l l e c t i o n s w e re used t o a d j u s t o u tp u t
c a l c u l a t e d f r o m g r a b s a m p l e s ( R i t t e n h o u s e 1969, R i t t e n h o u s e e t a l .
1970).
S am p les o f g r a z e d f o r a g e w e re c o l l e c t e d th r o u g h o u t t h e s tu d y
p e rio d s u sin g 4 e s o p h a g e a lly f i s t u l a t e d
r e v ie w e d by Van Dyne and T o r r e l l (1964).
freeze
d rie d
d ig e stib ility )
and
of
g round.
each
IVOMD
sam p le
w as
cow s.
The t e c h n i q u e w a s
E x tr u s a was f r o z e n and l a t e r
(in
v itro
d e te rm in e d
o rg a n ic
u sin g
m o d i f i c a t i o n o f th e , T i l l e y 1arid T e rry te c h n i q u e ( H a r r i s
m a tte r
th e
B arnes
1970).
Rumen
f l u i d f o r t h e IVOMD t r i a l s was c o l l e c t e d from rumen f i s t u l a t e d cows on
a 60% d i g e s t i b l e (IVOMD) a l f a l f a h a y d i e t .
The h a y w a s u s e d a s t h e
s t a n d a r d f o r t h e IVOMD c o m p ariso n s.
F e c a l o u tp u t and f o r a g e d i g e s t i b i l i t y
e s ti m a t e s w ere used to
e s ti m a t e in ta k e u sin g th e f o llo w in g eq u atio n :
g D a i l y f e c a l o u tp u t (OMB)
g o r g a n i c m a t t e r i n t a k e = —------------------------------------------I - IVOMD o f d i e t
T ab le 6 g iv e s a c o m p le te l i s t of th e c a l c u l a t i o n s u sed to e s t i m a t e
t o t a l o rg a n ic m a tte r in ta k e .
33
T ab le 6 .
E s t i m a t i o n o f f e c a l ouput and f o r a g e i n t a k e from f e c a l g ra b
s am p les.
Item
D e sc rip tio n
A
PPM Chromium i n f e c a l sample
B
O rganic m a t t e r o f sample
C
Weight o f sample
0.6842
C o n v ersio n o f PPM Cr t o Cr2 Og
0.1
D i l u t i o n f a c t o r f o r a c i d ' d i g e s t i o n t e c h n iq u e
D
g Cr2 Og f e d p e r day
E
Cr2 Og r e c o v e r y ($ o f f e d )
DxE=F
A d ju s te d Cr2 Og f e d p e r day
0.6842xCxBxF
---------------------=G
AxO. I •
kg f e c a l o u tp u t p e r day
H
A djustm ent f a c t o r f o r each TRT group comparing
t o t a l c o l l e c t i o n w ith g ra b sam ples
HxG=I
A d ju s te d f e c a l o u p u t
J
Body w e ig h t i n kg
(I/J)x 1 0 0 = K
L
F e c a l o u t p u t a s a % o f body w e ig h t
•.
.
IZI-L=M
(MZJ)x100=N
Forage d i g e s t i b i l i t y (IVOMD)
T o t a l i n t a k e (kgZday)
T o ta l i n t a k e (% BW)
Cows w e r e w e i g h e d a n d c o n d i t i o n s c o r e d i m m e d i a t e l y b e f o r e and
a f t e r th e s tu d y p e r io d s .
I n t e r m e d i a t e w e i g h t s an d c o n d i t i o n s c o r e s
w e re t a k e n once d u r i n g t h e 1985 s tu d y p e r io d .
C o n d itio n s c o r e s w ere a
34
v i s u a l and p a l p a b l e s c o r e f r o m one t o t e n ( t h i n t o f a t ) (L aM o n ta g n e
1981).
B e h a v io r E v a l u a t i o n ■
V i b r a c o r d e r s w e re u sed t o r e c o r d t h e t i m e s p e n t g r a z i n g .
Use of
v i b r a c o r d e r s i s d e s c r i b e d by S t o b b s (I 9 7 0 ), S t r i c k l i n e t a l . (1 97 6 ),
Bueno and Ruckebusch (1979),
and Adams (1984a).
each
5,
o f 3 age
groups,
3,
and 7 y e a r s
v i b r a c o r d e r s and g r a z i n g a c t i v i t y
>
F e b r u a r y 27.
I
I n 1984, 4 cows from
o ld ,
w ere f i t t e d
w ith
was r e c o r d e d betw ee n J a n u a r y 9 and
'I
I n 19 8 5 ,
4 cow s f r o m e a c h t r e a t m e n t g r o u p an d t h e
c o n t r o l group w ore v i b r a c o r d e r s from J a n u a r y 3 to F e b ru a ry 28.
b o th y e a r s ,
cow s w e a r i n g v i b r a c o r d e r s
p e d o m e te r s .
In d iv id u a l
w ere
a lso
fitte d
During
w ith
cows w ore t h e same v i b r a c o r d e r and pedom eter
th r o u g h o u t t h e r e c o r d i n g p e r io d .
P e d o m e te rs were s t r a p p e d t o e i t h e r
f r o n t f o o t i n 1984, b u t r e m a in e d on t h e l e f t f r o n t f o o t th r o u g h o u t t h e
1985 t r i a l .
V ib r a c o r d e r c h a r t s w ere r e a d to in c lu d e o n ly g r a z i n g o r n o t
g r a z i n g , no o t h e r l e v e l s o f a c t i v i t y w e r e a s s i g n e d .
w e re rounded t o 15 m in u te i n t e r v a l s .
G ra z in g tim e s
Each day was d i v i d e d i n t o t h r e e
p e r i o d s : 7AM t o 1PM, IPM to 7PM, and 7PM t o 7AM.
The number of h o u r s
s p e n t g r a z i n g d u r i n g e a c h p e r i o d a n d e a c h day w e r e r e c o r d e d a s a.
p e r c e n ta g e of th e t o t a l num ber o f h o u r s i n t h a t p e r io d .
w e re r e a d and z e r o e d e v e r y 6 to 8 days.
P e d o m e te rs
C a l i b r a t i o n was a c c o m p lish e d
by z e r o i n g and r e i n s t a l l i n g th e p e d o m e te r s , th e n moving th e cows w h ile
f o l l o w i n g w i t h a c a l i b r a t i o n w h eel.
The w heel i s 2 m i n c ir c u m f e r e n c e
and r e c o r d s th e number o f w heel r e v o l u t i o n s .
Cows w ere th e n p u t back
35
i n t h e c h u te and p e d o m e te r s removed,
read,
and compared t o t h e a c t u a l
d i s t a n c e r e c o r d e d by th e c a l i b r a t i o n w heel.
Ambient a i r t e m p e r a t u r e and r e l a t i v e h u m i d ity w ere r e c o r d e d each
y e a r u s i n g a h y g r o t h e r m o g r a p h p l a c e d on a n o r t h f a c i n g s l o p e i n t h e
a p p ro x im a te c e n te r of th e p a s tu re .
T e m p e r a t u r e an d h u m i d i t y w e r e
a v e ra g e d f o r eac h p e r i o d and each day u s i n g t e m p e r a t u r e s r e c o r d e d a t
tw o h o u r i n t e r v a l s .
D ata A n a ly s is
Data w e re a n a ly z e d f o r s i g n i f i c a n t d i f f e r e n c e s (p<.05) i n g r a z i n g
b e h a v i o r and t o . ta l in t a k e , among age g r o u p s and t r e a t m e n t groups.
w as a c c o m p lish e d u s in g
This
S t a t i s t i c a l A n a l y s i s S y stem ’s (SAS) General
L i n e a r Model (GLM) p r o c e d u r e ,
and th e a n a l y s i s o f v a r i a n c e p r o c e d u r e s
a v a i l a b l e i n MSUSTAT (Lund 1983).
The SAS GLM p r o c e d u r e was a l s o used
t o t e s t a l i n e a r r e g r e s s i o n model u s i n g tim e s p e n t g r a z i n g each day t o
e x p l a i n v a r i a t i o n i n t o t a l o r g a n ic m a t t e r i n t a k e :
I n t a k e = f ( D a ily G r a z in g Time)
A m o r e e x t e n s i v e m o d e l w as t e s t e d u s i n g t h e SAS S t e p w i s e p r e c e d u r e .
The
model was
u sed t o
e x p l a i n ■ v a r i a t i o n i n d a i l y g r a z i n g ti m e ; i t s
com ponents a r e fo u n d i n T a b le 7.
And f i n a l l y ,
A u to re g re ssiv e
t h e SAS A rim a p r o c e d u r e w as u s e d t o d e v e l o p a n
M oving A v e ra g e
(ARMA) m o d e l t h a t
d e sc rib e d
d a ily
g r a z i n g t i m e on any g iv e n day based on p a s t g r a z i n g t i m e s a lo n g w i t h
p r e s e n t and p a s t
te m p e ra tu re s.
T h is m o d e lin g
p r e v io u s ly been a p p lie d to a n im a ls ,
p r o c e d u r e had n o t
b u t w as u s e d i n t h i s s t u d y t o
d e t e r m i n e t h e e f f e c t o f p r e v i o u s e x p e r i e n c e s on p r e s e n t g r a z i n g
36
T ab le 7•
R e g r e s s io n model f o r e x p l a i n i n g v a r i a t i o n i n t h e d a i l y tim e
sp en t g ra z in g d u rin g w in te r.
T— ;
---------------------------------------—
Item
D e sc rip tio n
b0-7
C o n s ta n ts
I
T otal d a ily in ta k e
A
Age
IW
I n i t i a l W eight a t b e g in n in g o f s tu d y
T
Average d a i l y te m p e r a t u r e
H
Average d a i l y h u m id ity
DG
Day o f g e s t a t i o n
DT
D is ta n c e t r a v e l e d p e r day
GT
Time s p e n t g r a z i n g each day
R e g r e s s io n M odel:
GT=b0+ b 1( I ) + b 2 (A)+b3 (IW)+b4 (T )+b5 (H)+b6 (DG)+b7 (DT)
b eh av io r.
S uch a r e l a t i o n s h i p h a s b e e n s u g g e s t e d a s t h e b a s i s f o r
t h e r m a l a c c l i m a t i o n i n b e e f c a t t l e ( S e n f t and R it te n h o u s e 1985).
The
f i r s t s t e p i n t h i s p r o c e d u r e was an a u t o r e g r e s s i o n o f t e m p e r a t u r e and
d a i l y g r a z i n g ti m e .
The e f f e c t s o f a u t o r e g r e s s i o n w e re t h e n removed
w i t h a " p r e w h ite n i n g " p r o c e s s which t r a n s f o r m s an a u t o c o r r e l a t e d i n p u t
s e r i e s t o an u n c o r r e l a t e d ,
w h i t e n o i s e ( p u r e ly random) s e r i e s (Box and
J e n k i n s 1 976, C h a t f i e l d 1 980).
The tw o v a r i a b l e s w e r e t h e n c r o s s -
c o r r e l a t e d to e s t a b l i s h a tim e s e r i e s r e l a t i o n s h i p .
t h i s model a r e fo u n d i n T able 8.
C o m p o n e n ts o f
37
T ab le
8.
Time s e r i e s a n a l y s i s o f d a i l y g r a z i n g tim e b ased
g r a z i n g tim e s and p r e s e n t and p a s t te m p e r a t u r e s .
Item
past
D e sc rip tio n
GTd
G r a z in g tim e on day d
GT^_p
G ra z in g tim e on p t h day p r e v io u s t o d
Td
Average t e m p e r a t u r e on day d
Tp - q
Average t e m p e r a t u r e on q t h day p r e v io u s t o d
a ,b
on
C o n s ta n ts
A u t o r e g r e s s i v e Moving Average .(ARMA)
Model:
GTd=E1 GTd e ^ a 2 GTde2+ . . . + a ^ GTd_p+ T ^ b 1Tde1+b2Tde2+ . . .+bq Td_q
These m o d e lin g p r o c e d u r e s w e re u sed t o p ro v id e i n f o r m a t i o n and
c l a r i f i c a t i o n o f th e p a r a m e t e r s m e a su re d i n
d ev elo p ed a r e
not s t a t is tic a lly
c o m p le te ,
in c o m p l e t e a n a l y s i s o f th e o v e r a l l d a t a s e t .
th is
s tu d y .
The m odels
and t h e r e f o r e show an
As t h i s s tu d y c o n tin u e s
t h e m o d e l s a n d t h e i r v a r i a b l e s s h o u l d be r e - f o r m e d ,
and d i f f e r e n t
p ro c e d u re s u sed , i n an a t te m p t to i n c r e a s e th e s i g n i f i c a n c e of th e
m o d e ls and t h e outcome.
38
RESULTS
1Q84 T r i a l
Body Weight and C o n d it io n S co re
The t h r e e y e a r o ld cows e n t e r e d t h e s tu d y a t s i g n i f i c a n t l y lo w e r
w e i g h t t h a n t h e 7 y e a r o l d cow s.
The o t h e r a g e g r o u p s ( 4 , 5, and 6)
f e l l i n betw ee n t h e 3 and 7 y e a r o ld s .
T h is w e ig h t p a t t e r n p e r s i s t e d
t h r o u g h o u t t h e t r i a l w i t h w e i g h t c h a n g e s r a n g i n g f r o m - 1 0 . 8 t o +1.2
lb .
Mean w e i g h t changes among t h e age g ro u p s w ere n o t s i g n i f i c a n t l y
d iffe re n t.
C o n d itio n s c o r e s fo llo w e d th e w e ig h t p a tte rn ^
and, a g a in ,
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 c o n d i t i o n s c o r e c h a n g e am ong a g e g r o u p s
w e re seen.
A ll g ro u p s l o s t
c o n d itio n over th e w in te r.
The f i n d i n g s
a r e s u m m a rized i n A ppendix T ab le 19.
G ra z in g B e h a v io r
The o v e r a l l a v e r a g e o f d a i l y g r a z i n g t i m e w a s 8.8 h o u r s p e r day
o r 36.8 p e r c e n t o f t h e 24 h o u r p e r i o d b e g i n n i n g a n d e n d i n g a t 7AM.
T a b l e 9 g i v e s a c o m p a r i s o n o f g r a z i n g t i m e s f o r 3 age g r o u p s .
The
t h r e e y e a r o l d cow s s p e n t m o re t i m e g r a z i n g e a c h day t h a n t h e 5 o r 7
y e a r o ld cows.
The p ed o m e te r r e c o r d i n g s showed t h a t t h e 3 y e a r o l d 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 t h a n t h e 5 and 7 y e a r o ld cows.
Age group means
o f d i s t a n c e t r a v e l e d p e r day can be s e e n i n T able 9.
For a l l th e g ro u p s,
t h e a f t e r n o o n p e r i o d ( 1PM-7PM) w as m o s t
i m p o r t a n t f o r g r a z i n g w i t h an a v e r a g e o f 4.3 (72.0%) o f t h e 6 h o u r s
sp en t g razin g .
A s u b s t a n t i a l p o r t i o n o f t h e m orning p e r i o d (7AM-1PM)
39
T ab le
9.
D a ily g r a z i n g tim e s and d i s t a n c e s t r a v e l e d f o r 3
g r o u p s , 1984.
cow
age
G ra z in g Time ( % )
D is ta n c e
T r a v e le d (km)
Age
7AM-IPM
I PM-7PM
7PM-AM
3
5 4 .3a
7 5. I a
1 2 .7a
3 8 .7a
5 .6 a
. 5
4 8 . Ob
6 9 .2b
1 2 .3a
3 5 . 4b
4 .8 b
7
50. I b
7 2 . Oab
11.3 a
36 *2b
4 .7 b
D aily
a >'-’Means i n t h e same column w ith d i f f e r e n t s u p e r s c r i p t s a r e d i f f e r e n t
(p < .0 5 ).
was s p e n t g r a z i n g ; t y p i c a l l y ,
o f th e p e r io d .
g r a z i n g o c c u p ie d j u s t o v e r 3 h o u rs (51%)
N ig h ttim e g r a z i n g (7PM-7AM) was f a i r l y c o n s i s t e n t , but
r e p r e s e n t e d a r e l a t i v e l y s m a l l p o r t i o n o f each d a y 's g r a z in g .
G razing
d u r i n g t h i s p e r i o d was a d i s t i n c t l y i n d i v i d u a l a c t i v i t y w h i l e g r a z i n g
d u r in g t h e day u s u a l l y in v o lv e d groups.
F ig u r e 3 show s a t y p i c a l w i n t e r t e m p e r a t u r e
r e s u l t i n g g ra z in g b eh av io r.
s e c t i o n of th e g rap h ,
p a t t e r n and th e
The t e m p e r a t u r e s r e c o r d e d on t h e t o p
s h o u ld be: w i t h i n th e cow's t h e r m o n e u t r a l zone;
th e re fo re ,
th e g ra z in g p a t t e r n
situ a tio n s.
The m i d - s e c t i o n show s t h e g r a z i n g t i m e p e r c e n t a g e s f o r
e a c h d a y 's 3 p e r i o d s .
tim e m eans.
sh o u ld
be t y p i c a l
of u n s tre s s fu l
The b o t t o m p o r t i o n s h o w s t h e d a i l y
g razin g
D u rin g t h e s e s i x d a y s, d a i l y g r a z i n g tim e a v e ra g e d 4 1
p e r c e n t o f t h e day.
F i g u r e 4 sh o w s a much c o l d e r 6 d a y p e r i o d i n J a n u a r y .
The
a v e ra g e d a i l y g r a z i n g ti m e was lo w e r th a n d u r in g t h e w arm er p e r io d , 36
p e rc e n t.
On J a n u a r y I 6 t h e t e m p e r a t u r e d r o p p e d f r o m - 1 0 ° t o - 2 4 ° C .
40
TEMP
TIME
SPENT 40
GRAZING
24
HRS 30
SPENT 20
GRAZING in
F ig u re 3.
A n o r m a l w i n t e r t e m p e r a t u r e p a t t e r n an d t h e a s s o c i a t e d
g razin g a c t i v i t y .
a , b, c, d, e, f , g M eans r e pr e s e n t e d by s i m i l a r b a r s c o n t a i n i n g d i f f e r e n t
l e t t e r s are d if f e r e n t (p < .0 5 ).
41
TEMP
0C
%0F
TIME
SPENT
GRAZING
%0F
2 4 HRS
SPEN T
GRAZING
J a n . 14
F ig u re 4.
J a n . 15
G ra z in g a c t i v i t y
te m p e ra tu re s.
i
J a n . 16
J a n . 17
J a n . 18
J a n . 19
a s s o c i a t e d w i t h th e 1984 t r i a l ' s c o l d e s t
g> h, i , j Me a n g r e p r e s e n t e d by s i m i l a r b a r s c o n t a i n i n g d i f ­
f e r e n t l e t t e r s a r e d i f f e r e n t (p<.05).
42
The f o l l o w i n g d ay
t h e h ig h t e m p e r a t u r e w as - 2 2 ° and g r a z i n g tim e
d r o p p e d t o 30.0 p e r c e n t o f t h e d a y ,
p e rio d s.
H o w e v er,
a ll
th re e
on t h e 18 t h and 1 9 t h , g r a z i n g t i m e r o s e t o t h e
l e v e l i t h a d b e e n b e f o r e t h e 1 7 th .
p e rio d in c re a s e d
w ith a d ec re a se in
slig h tly
G r a z i n g t i m e i n t h e IPM t o 7PM
d u rin g t h i s
co ld p e rio d w h ile g ra z in g
d e c r e a s e d i n t h e m o rn in g and a t n i g h t .
T h i r t y - s e v e n p e r c e n t o f th e v a r i a t i o n i n d a i l y g r a z i n g ti m e was
e x p l a i n e d by th e s e v e n f a c t o r s i n c l u d e d i n t h e r e g r e s s i o n model.
o rd er of e n tra n c e in to
sta tistic s
are
The
t h e s t e p w i s e r e g r e s s i o n and t h e r e s u l t i n g
show n i n
T ab le
10.
O nly
tw o o f
th e
in d e p en d en t
v a r i a b l e s had a s i g n i f i c a n t e f f e c t on d a i l y g r a z i n g t i m e : h u m id ity and
(
day o f g e s t a t i o n .
I n c r e a s i n g h u m i d ity h ad a n e g a t i v e im p a c t on d a i l y
g r a z i n g t i m e w h i l e g e s t a t i o n had a s l i g h t l y p o s i t i v e e f f e c t .
T a b l e 11 s h o w s t h e r e s u l t o f t h e t i m e s e r i e s a n a l y s i s o f d a i l y
g r a z i n g t i m e and t e m p e r a t u r e .
G razin g t i m e on any g iv e n day was n o t
s i g n i f i c a n t l y e x p l a in e d by t h e a u t o r e g r e s s i v e m o v in g a v e r a g e m o d e l
u sin g
past
g razin g
tim e s
and p r e s e n t
and p a s t
te m p e ra tu re s
as
co v ariab les.
In ta k e
As s h o w n i n
T ab le
12,
age
d if f e r e n c e s i n t o t a l d a ily in ta k e .
o f body w e ig h t p e r day.
gro u p s e x h ib ite d
sig n ific a n t
The o v e r a l l mean i n t a k e was 0.87%
The l i n e a r r e g r e s s i o n model u s i n g i n t a k e and
d a i l y g r a z i n g tim e showed no s i g n i f i c a n t r e l a t i o n s h i p .
model a p p e a r i n T a b le 13»
no
D e t a i l s of th e
43
T ab le 10.
S te p w is e l i n e a r r e g r e s s i o n of 1 d a i l y g r a z i n g tim e , 1984.
E n tr a n c e
in to
Model
Source
S ig n ific a n t
P aram e ter
V alues
Mean
Alpha=. I d f S quare
f
Prob>f
Model r^
a t each
step
R e g r e s s io n
I
Humidity^
2
Day o f G e s t a t i o n
3
-0 .2 4
I
86.9
2 .8 9
0 .1 0
0.26
0 .1 4
I
119
3.96
0 .0 5
0 .3 2
I n i t i a l Weight
I
27.6
0.92
0 .3 5
0.34
4
Tem perature^
I
31.6
1 .05
0.31
0.37
5
D a il y I n ta k e
I
2.71
0 .0 9
0 .7 7
0.37
6
Age
I
1 .10
0 .0 4
0 .8 5
0.37
7
D a il y T ra v e l
I
0.11
0.00
0 .9 5
0 .3 7
27
30.1
R e s id u a l
I
D a ily a v e r a g e
T ab le
Lag
(Days)
11.
Time s e r i e s a n a l y s i s o f t o t a l d a i l y
a v e ra g e d a i l y t e m p e r a t u r e , 1984.
g razin g
tim e
and
C ross C o r r e l a t i o n s
-------——— —---------------------------------------------------------------------------- :—
C o e ffic ie n t
-I - .8 -.6 - .4 - .2
0 .2 .4 .6 .8 I
Marks two s t a n d a r d e r r o r s o r a l p h a = . 05
44
T ab le
12.
T o ta l d a i l y i n t a k e (OMB %BW) e s t i m a t e d from g ra b sam ples
and a d j u s t e d f o r Cr2 Og r e c o v e r y ( T u r n e r 1 9 8 5 ), 1984.
Age
T otal In ta k e
(0MB %BW)
3
0 . 9 1 + 0 . 05a
4
0 .8 9 ± P .0 4 a
5
0 .8 4 + 0 .0 4 a
6
0 .9 0 ± 0 .0 3 a
7
0 . 8 3 + 0 .0 3 a
a Means i n th e same column w ith th e same s u p e r s c r i p t a r e n o t d i f f e r e n t
(PC.0 5 ) .
T able 13.
L in ear r e g r e s s io n o f d a ily t o t a l in ta k e as r e l a t e d to d a ily
g r a z i n g tim e , 1984.
S ource
df
Mean
S quare
I
0 .0 2
48
0 .1 2
f
prob> f
Model r^
0 .7 2
0 .0 0
R e g r e s s io n
D a ily g r a z i n g tim e
R e s id u a l
0 .1 3
1085 T r i a l
Body Weight and C o n d it io n S c o re
As i n
1 984,
3 year
o ld
cow s e n t e r e d
and l e f t
th e t r i a l
s i g n i f i c a n t l y lo w e r w e i g h t s th a n some o f th e o l d e r age g r o u p s ;
at
th e re
was no s i g n i f i c a n t d i f f e r e n c e i n t h e w e i g h t change o r c o n d i t i o n s c o r e
change e x p e r i e n c e d by th e age groups.
Appendix T a b le 20.
These r e s u l t s a r e su m m arized i n
45
T h e r e w e r e no w e i g h t o r c o n d i t i o n s c o r e d i f f e r e n c e s am ong t h e
t r e a t m e n t g ro u p s a t th e b e g in n in g o f t h e t r i a l .
group
lo s t
w e ig h t
(I
kg)
d u rin g
s u p p le m e n te d gro u p s g a in e d w e i g h t .
s c o r e d u r in g t h e t r i a l , ,
c o n t r o l group.
th e
However, th e c o n t r o l
tria l
w h ile
a ll
of
th e
W h i le a l l g r o u p s l o s t c o n d i t i o n
t h e f a t group l o s t s i g n i f i c a n t l y l e s s t h a n t h e
The f a t group f i n i s h e d t h e t r i a l w i t h t h e h i g h e s t mean
c o n d itio n s c o re w ith o u t h av in g g ain ed th e m ost w e ig h t.
c o n d itio n s sc o re s fo r
W e i g h t s and
t r e a t m e n t g r o u p s a r e f o u n d i n A p p e n d ix T a b l e
21.
G ra z in g B e h a v io r
Appendix T a b le 22 shows t i m e s p e n t g r a z i n g by age g ro u p s i n 1985.
T h r e e y e a r o l d cow s g r a z e d s i g n i f i c a n t l y l o n g e r e a c h day t h a n t h e
o l d e r age g ro u p s.
D istan ce s tr a v e le d ,
a l s o i n T ab le 22, d id n o t show
th e same age p a t t e r n a s i n 1984.
Of t h e t r e a t m e n t g ro u p s,
cows r e c e i v i n g a n im a l f a t su p p lem en t
s p e n t l e s s tim e g r a z in g th a n d id th e
r e c e i v i n g b lo o d m eal s u p p le m e n t.
c o n t r o l g ro u p and th e group
The b lo o d meal group and t h e c o n t r o l
group d id n o t d i f f e r s i g n i f i c a n t l y i n g r a z i n g tim e ,
g r o u p 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 e a c h day .
b u t t h e blood meal
The c o r n g l u t e n m e a l
g r o u p t r a v e l e d m o re t h a n t h e c o n t r o l , s o y b e a n m e a l , a n d b l o o d m e a l
g ro u p s.
Mean g r a z i n g t i m e s and d i s t a n c e s t r a v e l e d f o r each t r e a t m e n t
group can be s e e n i n T ab le 14.
F i g u r e s 5 and 6 show t e m p e r a t u r e and g r a z i n g p a t t e r n s f o r tw o
p e rio d s
in
Jan u ary .
D u rin g
th e
t e m p e r a t u r e r o s e from - 1 8 ° t o O0C.
p e rio d
show n i n
F ig u re
5 th e
The a f t e r n o o n p e r i o d l o s t r e l a t i v e
46
T ab le
14.
D a ily g r a z i n g tim e s and t r a v e l o f each
1985.
tre a tm e n t
group,
G r a z in g Time (%)
D is ta n c e
T ra v e le d (km)
TRT
7AM-IPM
CON
5 8 . 6a
6 7 .8a
1 5 . Oa
3 9 .3a
4 .8 b
SBM
5 6 . I ab
6 5 . 7 ab
1 4 .5 a
3 7 . 6 bc
4 .5 b
FAT
5 4 . 5b
6 3 . 9b .
1 3 . 9a
3 6 .6 °
5 . Oab
CGM
5 4 . 2b
6 4 . 8 ab
1 3 .9 a
3 6 . 9 bc
5 .4 a
BM
5 6 .3 ab
6 5 . Oab
1 6 .2 a
3 8 .2 ab
3 .9 °
I PM-7PM
a , b , c l e a n s i n th e same
d if f e r e n t (p < .0 5 ).
column
7PM-7AM
w ith
D a ily
d iffe re n t
su p e rsc rip ts
are
im p o rta n c e i n th e d a ily g ra z in g sc h e d u le as th e te m p e ra tu re ro s e .
T h i s w a s a c c o m p a n i e d by a n i n c r e a s e i n m o r n i n g g r a z i n g a c t i v i t y .
T o t a l g r a z i n g t i m e d e c l i n e d on J a n u a r y 14, t h e day t h e t e m p e r a t u r e
peaked a t 0°.
The a v e r a g e o f d a i l y g r a z i n g t i m e s f o r t h e s e s i x d a y s
was 38.6 p e r c e n t ,
v e ry c l o s e t o t h e tw o 1984 p e r i o d s shown i n F ig u r e s
3 a n d 4.
F i g u r e 6 show s a t e m p e r a t u r e d e c l i n e fro m - 2 ° to -2 4 °C .
On
J a n u a r y 28 and 29 t h e te m p e r a t u r e d e c l i n e d s t e a d i l y , and d a i l y g r a z i n g
t i m e f e l l t o 28.4 p e r c e n t .
a fte rn o o n
in c re a se d
As t e m p e r a t u r e d e c l i n e d , g r a z i n g i n t h e
sig n ific a n tly
and
n ig h t
g ra z in g
decreased
s i g n i f i c a n t l y . B e fo re and a f t e r t h e 2 9 th , d a i l y g r a z i n g t i m e was c l o s e
t o 40 p e r c e n t .
The 6 day av era g e d a i l y g r a z i n g ti m e was 38.2 p e r c e n t ,
v e r y c l o s e t o t h e p e r i o d s shown i n F i g u r e s 3» 4 and 5.
47
-2
TEMP -6
°C - I O
-14
-18
7 am
%0F
TIME
SPENT
GRAZING
% OF
2 4 HRS
SPENT
GRAZING
4U
30
20
m
J a n . 12
J a n . 13
J a n . 14
J a n . 15
J a n . 16
J a n . 17
1985
F i g u r e 5.
A warming t r e n d and th e a s s o c i a t e d g r a z i n g a c t i v i t y .
a ,b ,c ,d ,e ,f,g ,h ,i
Means
rep resen ted
by s i m i l a r
bars
d i f f e r e n t l e t t e r s a re d i f f e r e n t (p < .0 5 ).
c o n ta in in g
48
TIME
SPENT
GRAZING
2 4 HRS 40
SPENT 30
GRAZING 20
Jan. 2 6
Jan. 2 7
Jan. 2 8
Jan. 2 9
Jan. 3 0
Ja n . 31
1985
F ig u re 6 .
A t e m p e r a t u r e d e c l i n e and t h e a s s o c i a t e d g r a z i n g a c t i v i t y .
a , b , c , d , e , f , g , h , i Means r e p r e s e n t e d
by s i m i l a r
bars
d if f e r e n t l e t t e r s a re d if f e r e n t (p < .0 5 ).
c o n ta in in g
49
F o r t h e 1985 t r i a l ,
t r e a t m e n t g ro u p w as added t o t h e l i s t o f
v a r i a b l e s i n t h e l i n e a r r e g r e s s i o n m o d e l.
T h i s m o d e l e x p l a i n e d ' 51
p e r c e n t o f t h e v a r i a t i o n i n d a i l y g r a z i n g tim e .
Once a g a i n ,
h u m id ity
was t h e f i r s t v a r i a b l e t o e n t e r t h e m odel, b u t w i t h a p o s i t i v e i n s t e a d
of n e g a tiv e e f f e c t.
T e m p e ra tu re e n t e r e d seco n d w i t h a n e g a t i v e e f f e c t
on d a i l y g r a z i n g tim e .
S t a t i s t i c a l d e t a i l s of t h e model, can be found
i n T a b l e 15.
T able 15.
S tep w ise l i n e a r r e g r e s s i o n o f d a i l y g r a z i n g tim e , 1985.
S ig n ific a n t
P a ra m e te r
V alues
A lpha=. I
df
E n tr a n c e
in to
Model
S ource
Mean
S quare
f
]Prob>f
Model r ^
a t each
ste p
R e g r e s s io n
I
Humidity^
2
Tem perature^
3
1 .4
I
302
17.5
0 .0 0
0 .3 7
-0 .5
I
6 7 .6
3 .9 2
0 .0 5
0 .4 2
D a ily I n ta k e
I
3 7 .7
2 .1 9
0 .1 5
0 .4 5
4
D a ily T r a v e l
I
4 4 .8
2 .6 0
0 .1 2
0 .4 7
5
Age
I
35.6
2 .0 7
0.16
0 .4 8
I n i t i a l Weight
I
2 7 .5
1.59
0 .2 2
0.50
7
Day o f G e s t a t i o n
I
12.3 ' 0 .7 2
0 .4 0
0.51
8
T re a tm e n t Group
I
5 .7 5
0 .5 7
0.51
32
17.2
■6
R e s id u a l
*1
0 .3 3
D a il y a v e ra g e
The t i m e s e r i e s a n a l y s i s o f 1985
shown i n T ab le 16.
g r a z i n g and t e m p e r a t u r e d a t a i s
G ra z in g tim e and t e m p e r a t u r e on t h e f i f t h p r e v io u s
day h ad a s i g n i f i c a n t ( a l p h a = . 0 5) p o s i t i v e e f f e c t on c u r r e n t g r a z i n g
50
T able
Lag
(Days)
16.
Time s e r i e s a n a l y s i s o f t o t a l d a i l y
a v e ra g e d a i l y t e m p e r a t u r e , 1985.
g razin g
tim e
and
C ro ssc o rre la tio n s
------------------------------------------- — —— ------------------------- --------------------C o e ffic ie n t
-I - .8 -.6 - .4 - .2
0 .2 .4 .6 .8
I
-
0.26
Marks two s t a n d a r d e r r o r s o r a l p h a = .05.
tim es.
However,
none o f t h e days b e tw e e n t h e f i f t h p r e v io u s day and
t h e c u r r e n t day h a d a n e f f e c t , a n d n o n e o f t h e d a y s p r e v i o u s t o t h e
fifth
day had an e f f e c t .
In ta k e
Grab s a m p le s t a k e n once d u r in g t h e t o t a l f e c a l c o l l e c t i o n p e r io d
a l l o w e d f o r t h e r e c o v e r y o f 6 0 .3 p e r c e n t o f t h e
s u p p le m e n t.
-fed w ith th e
Mean r e c o v e r y f o r each t r e a t m e n t group r a n g e d from 44 to
7 1 p e r c e n t , a lth o u g h t h e s e m eans w ere 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
( A p p e n d ix T ab le 23).
Chromic o x id e r e c o v e r y from s a m p le s ta k e n from each day’s t o t a l
c o l l e c t i o n s h o w e d a d i s t i n c t p a t t e r n ( A p p e n d ix F i g u r e 7 ).
H o w e v er,
LSD m u l t i p l e c o m p a r i s o n o f r e c o v e r y m e a n s s h o w e d f e w s i g n i f i c a n t
d iffe re n c e s
-
51
The CrgO^ r e c o v e r y f o r 1985 w as l o w e r t h a n p r e v i o u s s t u d i e s a t
Red B l u f f R e s e a r c h R anch ( T u r n e r 1 9 8 5 ).
The r e c o v e r y
le d
to
an
o v e r e s t i m a t i o n o f f e c a l o u tp u t com pared t o t o t a l f e c a l c o l l e c t i o n .
These co m p ariso n s a r e l i s t e d i n A ppendix T ab le 24.
A ppendix T ab le 25 shows t h e t o t a l o r g a n i c m a t t e r i n t a k e f o r each
t r e a t m e n t g r o u p a n d e a c h c o l l e c t i o n day .
These f i g u r e s have been
a d j u s t e d f o r CrgOg r e c o v e r y and g r a b s a m p le o v e r e s t i m a t i o n .
I n T ab le
17» th e amount o f s u p p le m e n t f e d each day h a s been rem oved i n o r d e r t o
a l l o w t h e c o m p a r i s o n o f f o r a g e i n t a k e am ong a l l g r o u p s .
The b lo o d
m eal and f a t g ro u p s e x h i b i t e d th e h i g h e s t d a i ly f o r a g e in t a k e .
The
c o n t r o l and c o r n g l u t e n m e a l g r o u p s c o n s u m e d t h e l e a s t f o r a g e e a c h
day.
T a b le 17.
D a ily f o r a g e o r g a n i c m a t t e r i n t a k e (%BW), 1985.
Day
T rea t­
ment
J a n 17
J a n 23
Feb 6
Feb 20
A ll Days
C
CON
0 .9 4 + 0 .1 0
I .01+0.07
0 .9 2 + 0 .0 8
1 .04+ 0.08
0 .9 8 ± 0 .0 4
SBM
1 .5 1 + 0 .0 9
I .0 7 ± 0 .0 5
1 .0 3 ± 0 .0 7
1.26±P .10
I .2 3 ± 0 .0 5 ab
FAT
I .13+ 0.14
0 .9 1 + 0 .1 4
1 .5 6 + 0 .1 7
2 .1 3 + 0 .4 3
1 . 4 4 + 0 .13a
COM
I .01+ 0.13
1 .0 2+ 0.79
I .0 0 ± 0 .1 0
1.08+ 0.13
1 .0 8 ± 0 .0 5 bc
BM
I .89+ 0.22
I .08+0.11
I .3 5 + 0 .1 3
1.94+ 0.33
1 .5 6 ± 0 .1 1 a
Mean
of a ll
TRT’ s
1 .3 0+ 0.07
de
f
I .02+ 0.04
ef
I • 17±0.06
d
1 .49±P.13
1.25
a »b>cMeans i n th e same column w ith d i f f e r e n t s u p e r s c r i p t s a r e
d if f e r e n t (p < .0 5 ),
d»e >^Means i n t h e same row w ith d i f f e r e n t s u p e r s c r i p t s a r e d i f f e r e n t
( p < .0 5 ) .
52
The l i n e a r r e g r e s s i o n model u s i n g i n t a k e and d a i l y g r a z i n g t i m e
a s v a r i a b l e s s h o w e d no s i g n i f i c a n t r e l a t i o n s h i p .
T a b l e 18 l i s t s
d e t a i l s o f t h e model.
T ab le 18.
L in ear r e g r e s s io n o f d a ily t o t a l in ta k e as r e l a t e d to d a ily
g r a z i n g ti m e , 1985.
S ource
df
Mean
S quare
f
prob> f
Model r 2
I
I .29
2 .1 3
0 .1 5
0 .0 5
40
0.60
R e g r e s s io n
D a ily G ra z in g Time
R e s id u a l
•X
53
DISCUSSION
F o rag e U t i l i z a t i o n and F o r a g in g P a t t e r n s
The, s t o c k i n g r a t e d u r in g both 1984 and 1985 was w e l l below t h a t
s u g g e s t e d by P ayne ( I 9 7 3 ).
H o w e v e r, o b s e r v a t i o n s a n d u t i l i z a t i o n
m e a s u r e m e n t s d i d n o t show e v e n g r a z i n g d i s t r i b u t i o n t h r o u g h o u t t h e
p a stu re ,
so a n o v e r a l l
sto c k in g
ra te
fig u re
d isc u ssin g fo rag e u t i l i z a t i o n p a tte rn s .
is
m i s l e a d i n g w hen
The p a s t u r e c o n t a i n s l a r g e
a r e a s w i t h a c o n s t a n t , s l i g h t s l o p e ; t h e s e a r e a s r e c e i v e d h e a v i e s t u se
w ith
a p p r o x im a te ly 75 p e r c e n t u t i l i z a t i o n o f th e key f o r a g e s p e c i e s .
A re a s w i t h c o n s t a n t , m o d e ra te s lo p e showed l i g h t g r a z i n g p r e s s u r e ,
a p p r o x i m a t e l y 30 p e r c e n t u t i l i z a t i o n .
The a r e a s c o n t a i n i n g s t e e p
s l o p e s w e re l e a s t u t i l i z e d show ing o n l y 15 p e r c e n t u t i l i z a t i o n of key
sp e c ie s.
T h i s u t i l i z a t i o n p a t t e r n w a s m o re p r o n o u n c e d i n I 984 t h a n
1 9 8 5 ; p e r h a p s t h e h i g h e r s t o c k i n g r a t e i n 1985, a n d d i f f e r e n c e s i n
f o r a g e c h a r a c t e r i s t i c s , f o r c e d more ev e n f o r a g e u t i l i z a t i o n .
T h r e e a r e a s i n t h e p a s t u r e w e r e u s e d by t h e co w s f o r s h e l t e r :
ro ck o u tc ro p s,
draw s
s h a llo w
s i t e s w i t h an o v e r s t o r y o f c o n i f e r s ,
c o n t a i n i n g s h r u b s and
b a sin
w ild ry e .
and deep
J u d g in g from
fecal
d ep o sits,
t h e cows s p e n t a c o n s i d e r a b l e amount o f ti m e i n t h e s e a r e a s ;
how ever,
t h e a r e a s d i d n o t c o n t a i n l a r g e q u a n t i t i e s o f key f o r a g e
s p e c i e s ( e x c e p t b a s i n w i l d r y e ) and so w e re p r o b a b ly n o t i m p o r t a n t
fo ra g in g a re a s.
The b e h a v i o r d a t a r e a d i l y show t h a t d a y l i g h t h o u r s w e r e p r e f e r r e d
o v e r n i g h t t i m e f o r g r a z i n g , and t h e h o u r s betw ee n IPM and 7PM a r e m ost
preferred ,
e s p e c i a l l y a t c o l d e r te m p e r a tu r e s *
grazin g a c t i v i t y
As t e m p e r a t u r e s warm,
spread out th ro u g h th e day; m o rn in g and a f te r n o o n
54
became e q u a l l y i m p o r t a n t and n i g h t a c t i v i t y
5).
al.
These f i n d i n g s a r e
(19 7 0 ),
i n c r e a s e d ( F i g u r e s 3 and
c o n s i s t e n t w i t h f i n d i n g s r e p o r t e d by Gary e t
A rn o ld and D u d z in s k i (1 9 7 8 ),
and S t r i c k l i n a n d K a u t z -
S canavy ( 1 9 8 4 ) .
C o n tr a ry t o t h e f i n d i n g s o f Hancock (1953) and S to b b s (1970), t h e
v a r i a t i o n among cows f o r d a i l y g r a z i n g t i m e i n t h i s s tu d y was low.
In
1984 t h e c o e f f i c i e n t o f v a r i a t i o n f o r d a i l y g r a z i n g t i m e r a n g e d from
13.7 t o 20.6 ( a v g . 1 8 .6 ) ; i n 1 985 t h e c o e f f i c i e n t s r a n g e d f r o m 12.8 t o
19.7 (avg.
15.6).
W in te r may im pose s t r i c t e r l i m i t s on b e h a v io r th a n
o th e r seasons, r e s u l t i n g i n l e s s v a r ia tio n .
E n v iro n m e n ta l S t r e s s
C o m p a riso n s
of
th e
b eh av io r
and w e a th e r
i m p o r t a n c e o f w e a t h e r a s a n e f f e c t on
d ata
in d ic a te
g ra z in g b eh av io r.
th e
F ig u re s 3
t h r o u g h 6 show r e a c t i o n s a n d a d j u s t m e n t s made t o d a i l y f o r a g i n g
p a tte r n s as te m p e ra tu re f lu c tu a te s .
H o w e v e r,
th e se
d a ta f a i l
to
e x p l a i n 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 s e e n i n tim e s p e n t
g razin g .
I n tw o s t u d i e s
( M a le c h e k a n d
S m ith
1 976,
Adams 1 9 8 4 a )
t e m p e r a t u r e w as r e p o r t e d a s b e in g c l o s e l y c o r r e l a t e d to t i m e s p e n t
g r a z i n g . Adams (1984a) d e v e lo p e d a p r e d i c t i v e t a b l e
g ra z in g
tim e
te m p e ra tu re s
as
a ir
te m p e ra tu re
d u rin g th a t
stu d y
decreased
ra n g e from
show ing d e c r e a s e d
(see
8 to
T ab le
-3 4 °C .
3).
The
G ra z in g
b e h a v i o r was r e c o r d e d w i t h v i b r a c o r d e r s from December 9 t o J a n u a r y 14.
The a u t h o r c a l c u l a t e d t h a t ,
b e g in n in g a t 0°C, f o r e v e r y 10° r e d u c t i o n
i n t e m p e r a t u r e , a one h o u r r e d u c t i o n i n d a i l y g r a z i n g t i m e c o u l d be
e x p e c te d .
I n d ic a tio n s of t h i s
r e l a t i o n s h i p w ere a l s o s e e n i n t h i s
55
s tu d y .
The d i f f e r e n c e i n a v e ra g e t e m p e r a t u r e betw ee n t h e two p e r i o d s
s h o w n i n F i g u r e s 3 a n d 4 w a s 16.6°C .
T h i s w a s a c c o m p a n i e d by a 1.2
h o u r r e d u c t i o n i n ' a v e r a g e d a i l y g r a z i n g ti m e .
d id n o t e x p la in a s u b s t a n t i a l
p o rtio n
However,
te m p eratu re
of th e v a r i a t i o n in
d a ily
g r a z i n g t i m e d u r in g t h i s s tu d y . A lso, a s s e e n i n F i g u r e 6, r e d u c t i o n s
i n g r a z i n g t i m e w i t h c o l d e r t e m p e r a t u r e s may be o n ly te m p o ra ry .
Adams
and F i g u r e s 3 and 4 s u g g e s t a s t r a i g h t f o r w a r d r e l a t i o n s h i p b e t w e e n
t e m p e r a t u r e a n d g r a z i n g t i m e , t h e r e g r e s s i o n m o d e l s a n d F i g u r e 6 do
n o t.
T e m p e ra tu re and h u m i d ity by t h e m s e lv e s d e s c r i b e a p o r t i o n o f t h e
th e r m a l e n v iro n m e n t, and w ere somewhat r e l a t e d t o d a i l y g r a z i n g ti m e
a s s e e n by t h e i r e a r l y e n t r a n c e i n t h e r e g r e s s i o n m o d e l s .
may n e e d t o be c o m b in e d w i t h w i n d s p e e d ,
But t h e y
b a ro m e tric p re ssu re ,
and
r a d i a n t h e a t l o s s o r g a i n t o d e v e lo p a t h e r m a l in d e x t h a t would more
c o m p le te ly d e s c r ib e th e th e rm a l e n v iro n m e n t as i t
is
re la te d
to
g r a z i n g b e h a v io r .
The r e l a t i v e
c o n sta n c y
of
d a ily
g ra z in g
in d e p e n d e n c e o f g r a z i n g tim e and t e m p e r a t u r e s e e n i n
in d i c a t e a la c k o f s e v e re e n v iro n m e n ta l s t r e s s .
tim e s
and t h e
th is
s tu d y may
When d a i l y g r a z i n g
d e c r e a s e d i t d id so i n c o n j u n c t i o n w i t h s e v e r e t e m p e r a t u r e changes (up
or
d o w n ),
but
re m a in e d
lo w
fo r
one
i n d i c a t i o n of a c u te th erm al s t r e s s ;
day
o n ly .
T h is
may
be a n
o t h e r s t u d i e s (W e b ste r and Young
1 9 7 0 , S l e e 1971) h a v e s h o w n t h a t a c u t e s t r e s s i s a c c o m p a i'n e d by a
d e c lin e in in tak e.
a p p ro x im a te ly
However, a t no tim e d id d a i l y g r a z i n g r e m a in below
40 p e r c e n t f o r
m ore th a n
one d a y ,
even i f
th e
t e m p e r a t u r e change p e r s i s t e d , and e v e n t h o u g h r e c o r d e d t e m p e r a t u r e s
56
r a n g e d f r o m 8 ° t o - 2 6 °C. Change i n t h e d a i l y g r a z i n g s c h e d u l e s h o w s
d e f in i te behavioral adjustm ent as tem peratures f lu c a tu a te ,
prolonged
change i n t o t a l
daily
b u t l a c k of
g r a z in g tim e as d a i l y sc h e d u le s
c h a n g e d may i n d i c a t e a l a c k o f p h y s i o l o g i c a d j u s t m e n t .
w ords,
behavioral
adjustm ents
physiologic adjustments.
w ere
made
w ithout
In o th e r
the
need
of
Perhaps b e h a v i o r a l a d j u s t m e n t s a l l o w th e cow
to r e m a in p h y s i o l o g i c a l l y s t a b l e d u rin g ti m e s o f a c u te s t r e s s . This
e o n s l u s i o n i s - s i m i l a r t o o n e made by S e n f t a n d E i t t e n h b u s e ( 1 9 8 5 ) .
They pr op os e " b e h a v i o r a l
a c c l i m a t i o n " a s a "mechanism f o r o f f s e t t i n g
STTS ( s h o r t t e r m t h e r m a l s t r e s s ) " .
In t h i s study, such b e h a v io ra l
a c c l i m a t i o n i n v o l v e d a d j u s t m e n t s o f w he n d u r i n g t h e day t h e cows
grazed,
but d id n o t n e c e s s a r i l y in v o l v e a d ju s tm e n t of t o t a l d a i ly
g razin g tim e.
I f t h e cow s w e r e r e m o v e d f r o m t h e i r TNZ f o r b r i e f
p e r i o d s , a d j u s t m e n t s w e r e made q u i t e r a p i d l y a n d t h e co w s q u i c k l y
r e t u r n e d t o nor ma l p h y s i o l o g i c s t a t u s .
Young (1981) e s t i m a t e d t h e l o w e r c r i t i c a l t e m p e r a t u r e of t h e dry
p r e g n a n t cow t o be =20o C,
t o be - 2 3 0C.
W eb s te r (1970a) r e p o r t e d t h i s t e m p e r a t u r e
These two e s t i m a t e s o f t h e l o w e r boundary o f t h e TNZ a r e
s u p p o r t e d by t h i s s tu d y.
t h e i r TNZ down t o ,
I t would a p p e a r t h a t t h e s e cows r e m a i n e d i n
and p o s s i b l y below, - 2 3 ° .
R e s u l t s of t h e t i m e s e r i e s a n a l y s i s a l s o i n d i c a t e t h a t cows w er e
not fo rced to r e - a c c l i m a t e them selves during e i t h e r w in te r.
Grazing
t i m e on an y g i v e n day w a s i n d e p e n d e n t o f p r e v i o u s g r a z i n g t i m e a n d
present
and
past
E i t t e n h o u s e (1985).
tem perature.
This
is
supported
by
Senft
and
T h e i r " t h e r m a l a c c l i m a t i o n model" i s based on th e
c o n c e p t t h a t p h y s i o l o g i c a l a c c l i m a t i o n d e p e n d s on a t i m e l a g t h a t
57
a llo w s th e i n t e g r a t i o n of e x p e rie n c e over tim e.
The t i m e s e r i e s
a n a l y s i s would i n d i c a t e t h a t s uch i n t e g r a t i o n and a c c l i m a t i o n was n o t
o c c u r r i n g ; t h e r e f o r e , t h e cows w e r e w i t h i n t h e i r TNZ.
F or age I n t a k e
I n t a k e e s t i m a t e s i n 1985 w e r e s i m i l a r t o t h o s e o f t h e p r e v i o u s
s t u d y a t Bed B l u f f Ranch (T ur n er 1985).
E s t i m a t e s i n 1984 were l o w e r
t h a n t h e I 985 e s t i m a t e s a n d s l i g h t l y l o w e r t h a n t h e p r e v i o u s s t u d y .
The o v e r a l l i n t a k e a v e r a g e f o r 1984 was 0.87 p e r c e n t of body w e i g h t ,
f o r 1985 i t was 1.25 p e r c e n t ,
and i n t h e s tu d y by Turn er ( 1985) i n t a k e
r a n g e d f r o m 0.8 t o 1.4 p e r c e n t w i t h a n a v e r a g e o f a b o u t 1.1 p e r c e n t .
These i n t a k e
d i f f e r e n c e s may s t e m f r o m t h e f o r a g e
p o r t i o n of t h e i n t a k e e q u a t i o n .
vitro
d ig estib ility
used i n t h i s
study)
Holechek e t a l .
d ig e stib ility
(1986) s t a t e d t h a t i n
t e c h n i q u e s u s i n g a 48 hour i n c u b a t i o n p e r i o d (as
poorly e s tim a te fo rag e
d ig e stib ility .
-True
d i f f e r e n c e s i n d i g e s t i b i l i t y among y e a r s , e r r o r s i n e s o p h a g e a l e x t r u s a
c o l l e c t i o n s , and e r r o r s i n i n v i t r o te c h n i q u e co u ld a l l a c c o u n t f o r
i n t a k e d i f f e r e n c e s s e e n b et w ee n 1981 and 1985.
The model r e l a t i n g d a i l y i n t a k e t o d a i l y g r a z i n g t i m e f a i l e d t o
show a s i g n i f i c a n t r e l a t i o n s h i p .
th is failure.
F irst, intake i s
Again t h e r e may be tw o r e a s o n s f o r
a f u n c t i o n of t h r e e f a c t o r s :
grazing
t i m e , b i t e r a t e , and b i t e s i z e ( S p e d d i n g e t a l . a s c i t e d i n Chacon e t
al.
1976).
need to
Second,
These t h r e e f a c t o r s can o p e r a t e i n d e p e n d e n t l y and. a l l may
be q u a n t i f i e d
before a re la tio n s h ip
c a n be e s t a b l i s h e d .
e s t i m a t e s of f o r a g e i n t a k e w e r e made f o r o n l y 6 days i n 1984
58
and 4 days i n 1985.
E s t i m a t e s f o r more days may be r e q u i r e d b e f o r e a
r e l a t i o n s h i p can be e s t a b l i s h e d .
S u p p le m e n ts used i n 1985 had d e f i n i t e e f f e c t s i n 3 r e l a t e d a r e a s .
F i r s t , i t w o u l d seem t h a t s u p p l e m e n t l o w e r e d t h e c o s t o f o b t a i n i n g
forage.
Supplem ented
grazing,
b ut consumed more f o r a g e th a n th e u n s u p p le m e n te d group.
Second,
groups
trav eled
less
an d s p e n t
less
tim e
t h e h i g h e r i n t a k e o f s u p p l e m e n t e d co w s may i n d i c a t e a
s u p p l e m e n t e f f e c t on d i g e s t i o n ,
p o s s i b l y on p a s s a g e r a t e th r o u g h t h e
r e t i c u l o - r u m e n . F a s t e r p a s s a g e r a t e may h a v e b e e n a p r e q u i s i t e f o r
h i g h e r i n t a k e u n d e r t h e b u l k - l i m i t i n g c o n d i t i o n s i m p o s e d by m a t u r e
w in te r forage.
This i s
s u p p o r t e d by f i n d i n g s o f C a m p l i n g e t a l .
(1 9 6 2 ) , a n d B r a n i n e a n d G a l y e a n ( 1 9 8 5 ) . I n a d d i t i o n , t h e b l o o d m e a l
supplem ent w ith i t s
bypass p r o t e i n had th e l a r g e s t in t a k e e f f e c t .
P a rt of the d ig e s t iv e e f f e c t i n t h i s
indirect,
since i t
was
assumed t h a t b y pa ss p r o t e i n d i d n o t d i r e c t l y
a f f e c t rumen f e r m e n t a t i o n .
study
may
have
c a s e would have t o have been
Two o t h e r mechanisms n o t me as u re d i n t h i s
contributed
to
the
increased
intake
seen
w ith
s u p p l e m e n t : an i n c r e a s e i n rumen dry m a t t e r c o n t e n t and a n i n c r e a s e i n
ru m in a tio n tim e.
Welsh (1982) c o n cl u d ed t h a t r u m i n a t i o n was t h e most
i m p o r t a n t method of a c h i e v i n g p a r t i c l e s i z e r e d u c t i o n and p a r t i c l e
p a s s a g e (more i m p o r t a n t t h a n rum en m ic ro b ia l a c t i v i t y ) .
tim e
showed c l o s e
a s s o c ia tio n w ith
intake;
anim als
Rum ination
deprived
of
r u m i n a t i o n showed d e c r e a s e d i n t a k e and s p e n t f e e d i n g t i m e s r u m i n a t i n g
in s t e a d of eatin g .
And t h i r d , t h e s u p p l e m e n t s a p p e a r t o h a v e h e l p e d t h e cow s m e e t
th eir
m aintainence
requirem ent.
K leiber
(I 96 I ) . e x p r e s s e d
th is
59
r e q u i r e m e n t a s t h e s t a t e i n which a n i m a l s n e i t h e r l o s e nor g a i n body
substance.
is
Expanding on t h i s d e f i n i t i o n , t h e m a i n t a i n e n c e r e q u i r e m e n t
the le v e l
condition,
o f n u t r i t i o n r e q u i r e d t o m a i n t a i n body w e i g h t ,
c o n s t a n t body t e m p e r a t u r e ,
and a g r o w in g f e t u s .
body
I n 1985,
a l l s u p p le m e n te d cows g a i n e d w e i g h t , a p p r o x i m a t e l y t h e w e i g h t o f t h e i r
calf.
Also,
alm ost
t h e a n i m a l f a t s u p p l e m e n t h e l p e d t h a t group m a i n t a i n a n
co n stan t
body
cond itio n .
This
in
co n trast
to
the
u n s u p p le m e n te d cows t h a t g e n e r a l l y l o s t w e i g h t and l o s t s i g n i f i c a n t l y
more c o n d i t i o n t h a n t h e f a t group.
to
m ain tain in g
The su p p le m en te d cows w e r e c l o s e r
body s u b s t a n c e ,
and
th erefo re
m eeting
m a i n t a i nance r e q u ir e m e n t,
t h a n t h e u n s u p p l e m e n t e d cows.
surface
(i.e.
body
in dications.
tem perature
in
the
ear)
would
th e ir
Measuring
v erify
these
I t w ould g i v e a c o n t i n u o u s and a c c u r a t e i n d i c a t i o n of
t h e h e a t p r o d u c t i o n , h e a t l o s s , and m e t a b o l i c s t a t u s of th e a n im a l.
The p e r i o d i c v a s o d i l a t i o n and wa rming a t t h e s k i n s u r f a c e r e p o r t e d by
B l a x t e r a n d Wainman ( 1 9 6 1 ) s h o u l d i n d i c a t e n o r m a l w i n t e r m e t a b o l i c
status.
Other t e m p e r a t u r e p a t t e r n s may i n d i c a t e an i n a b i l i t y t o meet
t h e m a i n t a i nance r e q u i r e m e n t and r e m o v a l from t h e TNZ.
The s u p p le m e n t e f f e c t s r e p o r t e d h e r e a r e open t o q u e s t i o n i n two
areas,
d i g e s t i b i l i t y and n u t r i e n t b a la n c e .
When f o r a g e i n t a k e i s
e s t i m a t e d u s i n g e s t i m a t e s o f f e c a l o u t p u t and f o r a g e d i g e s t i b i l i t y , an
i n c r e a s e i n f e c a l o u t p u t may i n d i c a t e a n i n c r e a s e i n i n t a k e o r a
decrease
however,
in
d ig e stib ility .
digestibility
This
study
has assumed
the
form er;
changes w i t h s u p p l e m e n t were n o t me asu re d and
may r e p r e s e n t a p o r t i o n o f t h e e f f e c t s seen.
For i n s t a n c e , t h e an im al
f a t s u p p l e m e n t (which r e s u l t e d i n t h e h i g h e s t f e c a l o u t p u t ) may have
60
decreased forage d i g e s t i b i l i t y
by c o a t i n g t h e f i b e r p a r t i c l e s w i t h a
l a y e r of f a t and p r e v e n t in g or r e d u c i n g m i c r o b i a l a tta c h m e n t.
This
same mechanism may have d e c r e a s e d rumen d i g e s t i o n o f t h e soybean meal
i n the supplement,
t h u s t r a n s f o r m i n g t h i s s u p p le m e n t so t h a t i n s t e a d
o f p r o v i d i n g r u m e n d e g r a d a b l e p r o t e i n a n d b y p a s s e n e r g y i t may h a v e
p r o v i d e d b y p as s e n e r g y and p r o t e i n ,
protein.
and l i t t l e
or no rumen d e g r a d a b l e
Such a m e c h a n i s m may h a v e p r o d u c e d n i t r o g e n a n d e n e r g y
b a l a n c e s o t h e r t h a n t h o s e e x p e c t e d and assumed.
t h e rumen, i n t h i s c a s e ,
Nitrogen balance i n
may have been s i m i l a r t o t h a t e x p e c t e d i n t h e
u n s u p p le m e n te d gro u p ; a p o s i t i v e n i t r o g e n and e n e r g y b a l a n c e i n th e
lower g a s t r o i n t e s t i n a l
t r a c t may have o f f s e t rumen d e f i c i e n c i e s and
a l l o w e d f o r t h e p o s i t i v e e f f e c t s s e e n w i t h - f at s u p p le m en t.
I n 1984 and 1985 t h e r e s u l t s o f age group a n a l y s i s b r o u g h t o u t an
i m p o r t a n t f a c t o r i n a cow’s a b i l i t y
range.
I n b o t h y e a r s , t h e 3 y e a r o l d co w s w e r e s p e n d i n g t h e i r f i r s t
w i n t e r on ran ge .
mo re f o r a g e .
This group s p e n t more t i m e g r a z i n g w i t h o u t consuming
This s u g g e s ts t h a t g r a z in g e f f i c i e n c y in c r e a s e d w ith
rangeland experience.
able
t o m a i n t a i n i t s e l f on w i n t e r
to
low er
the
G r a z i n g may be a l e a r n e d b e h a v i o r w i t h cow s
n u tritio n al
cost
f a m i l i a r i z e them selves w ith w i n t e r range.
(
of
th is
activ ity
as they
61
SUMMARY
The two main n u t r i t i o n a l c o s t s f o r t h e r a n g e b eef cow a r e (I) t h e
m a i n t a i n e n c e r e q u i r e m e n t a n d (2) t h e l e v e l o f a c t i v i t y ,
g r a z i n g and t r a v e l .
especially
Bo th o f t h e s e c o s t s a r e h i g h i n w i n t e r due t o
e n v i r o n m e n t a l s t r e s s and t h e a s s o c i a t e d i n c r e a s e i n h e a t
production,
an d due t o t h e r e l a t i v e l y low n u t r i t i o n a l v a l u e o f m a t u r e d o r m a n t
forage.
these
Cows r e c i e v i n g p r o t e i n s u p p l e m e n t a r e b e t t e r a b l e t o m e e t
costs,
and a r e
able
to
rem ain p ro d u ctiv e under the harsh
c o n d i t i o n s imposed by t h e w i n t e r r a n g e e n v i r o n m e n t.
In
the
w in ters
of
1 984 and
198 5,
a study
w as c o n d u c t e d on
f o o t h i l l r a n g e l a n d i n s o u t h w e s t Montana t o e s t i m a t e f o r a g e i n t a k e , and
m e a su r e f o r a g i n g b e h a v i o r ,
o f s u p p le m e n te d and unsupplemented, cows i n
t h e t h i r d t r i m e s t e r of g e s t a t i o n .
In t h i s
intake
s tu d y ,
cows r e c e i v i n g p r o t e i n s u p pl em en t showed h i g h e r
t h a n u n s u pp le m en te d cows w i t h o u t s p e n d i n g more t i m e g r a z i n g .
T h i s s u g g e s t s a p o s i t i v e d i g e s t i v e i n f l u e n c e of 250g o f CP su pp le m en t
p e r day.
Of p a r t i c u l a r i n t e r e s t i s t h e b lo o d meal s u p p le m e n t (200g of
r u m e n d e g r a d a b l e p r o t e i n a n d 200g o f b y p a s s p r o t e i n ) w h i c h b r o u g h t
about the g r e a t e s t i n c re a s e i n d a ily fo rag e intake.
It is
d i f f i c u l t t o make c o n c l u s i o n s c o n c e r n i n g t h e r e l a t i o n s h i p
of f o r a g e i n t a k e and t h e t h e r m a l e n v i r o n m e n t .
intake,
D aily e s t i m a t e s of
though d i f f i c u l t t o o b t a i n and p r o c e s s , a r e n e c e s s a r y i n o r d e r
t o show how a c u t e and c h r o n i c co l d s t r e s s a f f e c t f o r a g e i n t a k e .
G r a z in g t i m e h a s shown an i m p o r t a n t b ut som ew hat am biguous
relatio n sh ip
to
tem perature
in
th is
study.
As t h e
tem perature
f l u c t u a t e d b et w e e n 8 and - 2 6 °C t h e d a i l y g r a z i n g s c h e d u l e s h i f t e d t o
62
i n c l u d e m o r e a f t e r n o o n g r a z i n g a n d l e s s m o r n i n g an d n i g h t g r a z i n g .
Also,
severe tem perature
daily
g razin g tim e.
changes caus ed a s h o r t (one day) d e c l i n e i n
T h e s e a d j u s t m e n t s may h a v e b e e n b e h a v i o r a l
r e a c t i o n s to acu te cold s t r e s s .
T h is s tu d y a l s o showed t h a t p a s t
grazing tim e,
and p a s t t e m p e r a t u r e d i d n o t have a
present tem perature,
s i g n i f i c a n t e f f e c t on p r e s e n t g r a z i n g ti m e.
Thi s may i n d i c a t e a l a c k
o f any c h r o n i c c o l d s t r e s s d u r i n g t h e t r i a l s .
U n f o r t u n a t e l y , t e m p e r a t u r e a l o n e i s n o t i n d i c a t i v e of t h e t h e r m a l
e n v i r o n m e n t.
An i n d e x t h a t c o n t a i n s t e m p e r a t u r e , h u m i d i t y , windspeed,
and b a r o m e t r i c p r e s s u r e may e x p l a i n a g r e a t e r p o r t i o n o f t h e v a r i a t i o n
i n b e h a v i o r s e e n i n cows on w i n t e r r a n g e .
63
RECOMMENDATIONS AND QUALIFICATIONS
Four of th e d a t a s e t s c o l l e c t e d d u r i n g t h i s s t u d y may n o t p r e s e n t
a c o m p l e t e o r c o m p l e t e l y a c c u r a t e i n d i c a t i o n o f t h e cow's s i t u a t i o n on
w i n t e r range.
Three o f t h e s e w ere m e n t i o n e d i n o t h e r p o r t i o n s of t h i s
t e x t , b u t w i l l be d i s c u s s e d h e r e , a l s o .
M o d ific a tio n of th e se fo u r
d a t a s e t s w o u l d p r o v i d e a m or e c o m p l e t e p i c t u r e o f w i n t e r f o r a g i n g
behavior.
P e d o m e t e r s may n o t g i v e a n a c c u r a t e i n d i c a t i o n o f t h e d ai ly d i s t a n c e t r a v e l e d by c a t t l e .
movement o f t h a t l e g ,
d irectly
Pedom eters a tta c h e d to th e l e g r e c o r d
but i t i s n o t alw ay s p o s s i b l e to t r a n s l a t e
fro m l e g movement to
d istance
trav eled
since
movement p r o d u c e s a d i f f e r e n t q u a n t i t y o f f o r w a r d m ot ion .
each le g
Given t h i s
i n a d e q u a c y , p e d o m e te r i n f o r m a t i o n i s n o t a c c e p t a b l e t o a l a r g e p a r t of
the s c i e n t i f i c
trav el
com munity,
rep resen ts
expenditure.
and i t i s
an im p o rta n t
b a s ic a lly ignored.
part
of a cow 's
d aily
Howe ver ,
energy
F i n d i n g a n a c c u r a t e m e a su r e of d i s t a n c e s t r a v e l e d would
h e lp a g r e a t deal i n e x p la in in g the n u t r i t i o n a l
w i n t e r r an g e.
I t may be p o s s i b l e ,
c o s t of s u r v i v i n g on
and w o r t h w h i l e ,
t o d e v e l o p a more
s e n s i t i v e r e c o r d i n g d e v i c e w i t h t h e g o a l o f more a c c u r a t e l y r e l a t i n g
movement t o t r a v e l .
A second a r e a of in a d e q u a te i n f o r m a tio n has been d a i ly in ta k e .
As m e n t i o n e d p r e v i o u s l y , d a i l y f e c a l g r a b s a m p l e s f r o m a p o r t i o n o f
th e herd,
previous
adjusted
studies,
using
w ould
to tal
g reatly
fecal
co llection
enhance
our
in th is
ab ility
c o n c l u s i o n s a n d show r e l a t i o n s h i p s b e t w e e n i n t a k e ,
environm ental fa c to r s .
as
to
behavior,
and
make
and
64
W eather
tem perature,
im p o rtan t
in fo rm atio n
hum idity,
part
of
should
w indspeed,
th is
also
and
in fo rm atio n
be
expanded to in c lu d e
barom etric
pressure.
An
w o u l d be d e t e r m i n i n g t h e
c o n t r i b u ti o n of each catag o ry to the o v e r a l l th e rm al environm ent.
T h i s may be a s t u d y i n i t s e l f ,
the
understanding
of
the
but would c o n t r i b u t e s u b s t a n t i a l l y t o
environm ental
pressures
placed
on t h e
animals.
Finally,
t h e e s t i m a t e s o f f o r a g e d i g e s t i b i l i t y have shown a g r e a t
deal of v a r ia tio n .
I f t h i s v a r i a t i o n i s a c t u a l , i t would be i m p o r t a n t
t o i n s u r e t h a t g r a z e d f o r a g e s a m p l e s be o b t a i n e d i n a l l a r e a s o f t h e
p a s tu re throughout the t r i a l .
R e c o r d i n g s a m p l e l o c a t i o n may h e l p
e x p l a i n some o f t h e v a r i a t i o n seen.
Also,
t h e i n v i t r o te c h n i q u e may
need t o be m o d i f i e d t o more c l o s e l y i m i t a t e a c t u a l rumen f e r m e n t a t i o n
conditions.
A r e c e n t s t u d y by H o l e c h e k e t a l . ( 1986) may p r o v i d e a
b a s i s f o r modifying t h i s technique.
Once a b a s e l i n e o f w i n t e r f o r a g i n g b e h a v i o r i s e s t a b l i s h e d , i t
may be e n l i g h t e n i n g t o s t u d y b e h a v i o r a t o t h e r t i m e s of t h e y e a r .
s p e c i a l i n t e r e s t m i g h t be O c t o b e r a n d N o v em b er ,
Of
t h e m o n t h s when
c h r o n i c c o l d s t r e s s and a c c l i m a t i o n t o c o l d a r e most l i k e l y t o oc cu r.
The o t h e r m a j o r a r e a of i n t e r e s t i n t h i s s tu d y , i s t h e s up ple m ent
and i t s e f f e c t on cow p erf or ma nce .
shown d e f i n i t e b e n e f i t s ,
Providing p r o te i n supplement has
but t h e r e r e m a i n two a r e a s o f concern.
m echanism s of p r o t e i n b e n e f i t a r e n o t u n d e rs to o d ,
bypas s p r o t e i n e f f e c t
especially
s e e n w i t h blood meal i n t h i s s tu d y .
Also,
The
the
the
e c o n o m i c s o f s u p p l e m e n t a t i o n , i n c l u d i n g w hen a n d how much t o f e e d ,
65
have n o t been s a t i s f a c t o r i l y d e t e r m i n e d .
Study of t h e s e two q u e s t i o n s
s h o u ld c o n t i n u e and expand i f p o s s i b l e .
So f a r t h e end p o i n t o f t h e s t u d y each y e a r h a s been body w e i g h t
and c o n d i t i o n changes,
i f t h i s e n d p o i n t w e r e r e - f o c u s e d i t may be
m o r e h e l p f u l i n e x p l a i n i n g a n d d e s c r i b i n g so me o f t h e e f f e c t s s e e n .
Body w e i g h t and c o n d i t i o n changes a r e one i n d i c a t i o n ,
inadequate
indication,
of w hether or not th e
m a i n t a i n e n c e r e q u i r e m e n t over t h e w i n t e r .
bu t p e r h a p s an
co w s h a v e m e t t h e
Me etin g t h e m a i n t a i n e n c e
r e q u i r e m e n t i s t h e o v e r a l l g oal and t h e r e may be o t h e r m e a s u r e s t h a t
would b e t t e r i n d i c a t e w h e th e r or n o t th e g o al i s b e i n g met.
a c c u r a t e m e a su r e of t h e amount o f a d i p o s e t i s s u e ,
show
the
extent
maintainence.
to
Also,
w hich
that
tissue
measuring s u r f a c e
was
A more
for instance,
being
would
u tilized
body t e m p e r a t u r e (i . e .
for
in the
e a r ) w o u l d i n d i c a t e i f t h e cows w e r e w i t h i n t h e i r TNZ a n d a b l e t o
m a i n t a i n t h e h e a t p r o d u c t i o n r e q u i r e d i n t h e w i n t e r r a n g e en v i ro n m en t.
66
LITERATURE CITED
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APPENDIX
79
Table 19 .
Body w e i g h t s
1984.
and
c o n d i t i o n s c o r e s f o r 5 cow age g ro u p s ,
Initial
Age
, (yrs)
Ending
Weight C o nd it ion i
(kg)
Score
Change■
Weight
C o n d it io n
Sco re
5.7°
503b
5.3°
-1 0 .5a
-0 .5 a
5.6° •
478b
5 . I bc
+1.2a
-0 .6 a
- 1 0 . 8a
-0 .4 a
C o n d it io n
Score
Weight
7
518a
6
477a b
5
482ab
5 . 5 bc
4 7 I ab
5 . 2 bc
4
470ab
5 . I ab
470ab
4.8b
-6 .4 a . -0.4a
3
43 5b
4.8a
435a
4.3a
-3 .6 a
a , ^»0Means i n t h e same column
d i f f e r e n t (p<.05).
T ab l e 20.
Body w e i g h t s
1985.
In itial
Age
(yrs)
Weight C o n d it io n
(kg)
Score
and
with
different
-0 .4 a
superscripts
are
c o n d i t i o n s c o r e s f o r 4 cow age gr oups,
Ending
Weight
Change
C o n d it io n
Sc o re
Weight
Condition
S co re
6
502ab
6 .Ib
534b
5 .Ib
32a
-0 .9 a
5
537b
5.8b
56lb
4 . 7 ab
24a
-1.2a
4
495ab
5 .Ia
542b
4 . 3 ab
41a
-0 .7 a
3
461a
4.9a
490a
3.9a
29a
- I . Oa
a >^Means i n th e same column w i t h d i f f e r e n t s u p e r s c r i p t s a r e d i f f e r e n t
(p<.05).
80
Tabl e 21 .
Body w e i g h t s and c o n d i t i o n s c o r e s o f each t r e a t m e n t group,
1985.
In itial
TRT
Ending
Weight C o n d it io n
(kg)
Score
Weight
Change
C o n d it io n
S co re
Weight
Condition
Sco re
CON
501a
5.4a
500a
3 .9 a
-Ia
-1 .4 a
SBM
523a
5.6a
556a
4 . 5 ab
33b
- I . I ab
FAT
520a
5 . Ta
547a
5 . 3b
27b
- 0 . 4b
CGM
502a
5.6a
546a
4 . 5 ab
44b
- K I ab
BM
499a
5.3a
538a
4 . 6 ab
37b
- 0 . 7 ab
3. b
’ Means i n t h e same column w i t h d i f f e r e n t s u p e r s c r i p t s a r e d i f f e r e n t
(p<.05).
Ta b le 22,.
D a il y g r a z i n g
gr ou ps , 1985.
times
and d i s t a n c e s t r a v e l e d f o r 4 cow age
G r a z in g Time ( %)
Age
7AM-1PM ■ I PM-7PM
7PM-7AM
Dail y
D is ta n c e
T r a v e l e d (km)
3
6 0 . 9a
68. 7a
14.I a
39.4a
4 . Ob
4
5 5 .8 ^
6 6 .Sab
11. 2b
3 6 . 3b
3.8b
5
53.9^
6 4 . 8b
1 4 .8a
37.3b
7 .9 a
6
55.Ib
6 4 .2b
1 5 . 9a
37.7b
3 . 7b
'
i n t h e same column w i t h d i f f e r e n t s u p e r s c r i p t s a r e d i f f e r e n t
(p<.05).
a ’ ^M eans
81
Ta b le 23.
Chromic o x i d e r e c o v e r y (% f e d ) , 1985.
T r ea tm e nt Group
Source
SBM
Samples from
to ta l collection
95 .7
Grab samples
71 . I a
FAT
a
CGM
a
BM
a
A ll TRTf s
a
60.9
7 0 .2
102
43.7a
6 2 .4a
64.I a
82.3
•
a Means i n th e same row w i t h th e same s u p e r s c r i p t a r e n o t
(p <. 05)
T a b l e 24.
60 .3
different
D a i l y f e c a l o u t p u t (0MB % BW) e s t i m a t e d u s i n g t o t a l
c o l l e c t i o n and CrgOg, 1985.
fecal
T rea tm en t
Method
Tot al^
C ollection
CON
SBM
FAT
ab
a
CGM
b
BM
ab
ab
C
0.56
0 .6 3
0.71
Samples^
from t o t a l
collection
-----
a
0 .6 8 '
0 .7 0
0 .8 9
1.10
0.90
Grab
----
0.94a
1.00a
I .IOa
1.40a
I .IOe
s a m p le st > 3
0 .6 0
Al l TRT
0.60
ab
a
0.64
b
d
cL b
’ Means i n t h e same row w i t h d i f f e r e n t s u p e r s c r i p t s a r e d i f f e r e n t
(p<.05).
c > ’ eMeans i n t h e same column w i t h d i f f e r e n t s u p e r s c r i p t s a r e
d i f f e r e n t (p<.05).
■‘Average f o r 24 h o u r s c a l c u l a t e d from a 96 hour c o l l e c t i o n p e r i o d .
^ E s t i m a t e d w i t h chromic o x id e t e c h n i q u e .
^Grab s am pl es t a k e n once d u r i n g t h e 96 hour t o t a l c o l l e c t i o n p e r i o d .
82
Ta b le 25.
T o t a l d a i l y i n t a k e (0MB % BW), 1985.
Day
Treat­
ment
J a n 17
J a n 23
Feb 6
Feb 20
Mean o f
Al l Days
CON
0 . 9 4 + 0 .1 0 °
I . 0 1 + 0 . OTa
0.92+0.08°
1 . 04 +0 .08 °
0 . 9 8 + 0 .0 4 d
SBM
I . 6 2 + 0 . 09ab I . I 8 ±0. 05 a
1 . 14 ±p .0 7 bc 1 . 3 7 + 0 . 10bc
1.3 4+0 .05 b°
FAT
I . 2 8 + 0 . I 4bc I . 0 6 + 0 . 14a
I . 7 1 + 0 . 17a
2.28+0.43a
I . 5 9 + 0 . 14ab
CGM
I . 2 3 + 0 . I 3bc I . 2 4 + 0 . 09a
1 . 1 2 + 0 . 1 Obc 1. 20 +0. 13 °
1 . 20+0.06° d
BM
2.02+p.22a
I . 4 8 + 0 . 13ab 2 . 0 7 + 0 . 3 3 ab
I . 6 9 + 0 . 12a
Mean
a l l of
TRT’ s
I .21+0. I l a
ef
I .45+0 .08
S
1,1 5+0 .04
e
fg
1. 31 +0. 07
I .62+0.14
1.37
a > b , c , d Means i n th e same GOlumn w i t h d i f f e r e n t s u p e r s c r i p t s a r e
d iffe re n t (p<.05).
e > >^Means i n t h e same row w i t h d i f f e r e n t s u p e r s c r i p t s a r e d i f f e r e n t
(p<.05).
83
120
- -
110- -
Cr O
recovery
IOO-
9 0 --
80-
70--
60 -■
Day
I
Day
Feed
SBM
F i g u r e 7.
2
Day
3
day
BM
Day
Feed
FAT
4
day
CGM
Chromic o x i d e r e c o v e r y p a t t e r n d u r i n g t o t a l f e c a l
c o l l e c t i o n , I 985.
MONTANA STATE UNIVERSITY LIBRARIES
3
762 100 3603 3
Main
Jf37Q
D922
c o p .2
Dunn, Roger W i l l i am
Physiological and ben a v io ra l responses o f . . .
Main
N378
D922
co p . 2
4