Comparison of breeding management systems using either one or two injections of PGF2a in suckled
beef cows
by Gail Milton Vennes
A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE
in Animal Science
Montana State University
© Copyright by Gail Milton Vennes (1982)
Abstract:
Three herds of suckled beef cows (2 to 10 years old; n=656), at least 50 days post-partum, were used in
two trials. In trial 1, members within a herd were assigned randomly to three groups: 1) controls,
artificially inseminated (Al) 12 hr after detected estrus; 2) cows receiving two injections of 25 mg
PGF2α (free acid equivalent) 11 days apart followed by Al 12 hr after detected estrus until 80 hr
post-treatment at which time all members not yet bred were inseminated (LL-AI-E-80); and 3) cows
receiving the same PGF2α treatment as LL-AI-E-80 but inseminated only at 80 hr post-treatment
(appointment bred) (LL-AI-80). Observations of all groups for estrus began immediately after the
second PGF2α injection and were made twice daily for a 6-day period. PGF2α-treated cows, which
were detected in estrus after day 4 were reinseminated utilizing a genetic marker to determine sire of
calf. Clean-up bulls were introduced 12 hr after the last Al for the remainder of a 50-day breeding
season. The rate of detected estrus during the first 4 days of detection was signficantly higher (P<.05)
in the PGF2α -treated cows than in the controls. Cumulative Al pregnancy rates (no. pregnant - no. in
group) by day 4 of breeding were: 12, 45 and 39? for controls, LL-AI-E-80 and LL-AI-80,
respectively; the percent pregnant for LL-AI-E-80 and LL-AI-80 was higher (P<.05) than controls but
did not differ (P>.05) from each other. Total pregnancy rates of cows detected (no. pregnant - no.
detected) in 4 days were not different (PX05) among groups. Thirty-nine percent of the PGF^-treated
cows that were not detected in estrus during the 6 days post-treatment were pregnant from the 80 hr
breeding; none of those detected on days 5 or 6 were pregnant to this breeding. In trial 2, controls in
trial 1 from two herds (n=H4) were injected with PGF2α if they had not been detected in estrus by day
4.5 and Al was continued for 4 more days (AI-L-AI-E). Reproductive performance of this group was
compared with that of their LL-AI-80 herdmates (n=109). First Al pregnancy rates (no. pregnant to 1st
Al -no. inseminated) were 68 and 47? (P>.05) for AI-L-AI-E and LL-AI-80, respectively. Total Al
pregnancy rates (no. pregnant to 1st Al - no. in group) were 54 and 47? (PX05) for AI-L-AI-E and
LL-AI-80, respectively. Cumulative calving rates (no. calved - no. in group) by day of calving season
for AI-L-AI-E and LL-AI-80, respectively, were day 10, 60 and 64?; day 38, 75 and 89? (P<.05) and
day 60, 87 and 93?. Time of onset of estrus up to 96 hr after the double PGF2α injection system did not
influence pregnancy rate to an 80 hr breeding. The number of Al calves produced in either the
AI-L-AI-E or LL-AI-80 system did not differ, but more calves were born in the first 38 days of calving
after the LL-AI-80 plus clean-up bull system than after the AI-L-AI-E plus clean-up bull system. STATEMENT OF PERMISSION TO COPY
In p re s e n tin g t h i s
th e sis
in
p a rtia l
fu lfillm e n t
of
th e
r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t M ontana S t a t e U n i v e r s i t y , I
a g re e t h a t th e L ib ra r y s h a l l make i t f r e e l y a v a i l a b l e f o r in s p e c tio n .
I f u r t h e r a g re e t h a t p e rm is s io n f o r e x te n s iv e copying o f t h i s t h e s i s
f o r s c h o l a r l y p u r p o s e 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 absence, by th e D ir e c to r o f L i b r a r i e s .
I t i s u n d e rsto o d t h a t any
copying or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a in s h a l l not be
a llo w ed w ith o u t my w r i t t e n p e rm issio n .
S ig n a tu r e
L
Ji.
/ / / < fS 'flsyi/T ld / )
/7,
/ffna.
^
COMPARISON OF BREEDING MANAGEMENT SYSTEMS USING EITHER
ONE OR TWO INJECTIONS OF PGF2d IN SUCKLED BEEF COWS
by
GAIL MILTON VENNES
A t h e s i s s u b m itte d i n p a r t i a l f u l f i l l m e n t
of th e re q u ire m e n ts f o r th e degree
of
MASTER OF SCIENCE
in
Animal S cience
Approved:
___
TftL/^
Cti%irman, G r a d u a l Committee
Po
X
e
Head, Major Department
.
G raduate Dean
MONTANA STATE UNIVERSITY
Bozeman, Montana
March, 1982
ill
ACKNOWLEDGEMENTS
In itia lly ,
I w ould l i k e t o a c k n o w le d g e t h e l a t e Dr. Edward L.
Moody f o r g i v i n g me t h e o p p o r t u n i t y t o p u r s u e a g r a d u a t e d e g r e e i n
Animal Science.
His th o u g h tf u l c o n s i d e r a t i o n and encouragement w i l l
alw ays be remembered.
Also, I w ish t o e x p re ss g r a t i t u d e to Mr. R. P.
A n s o t e g u i , Dr. J . G. B e r a r d i n e l l i ,
Dr. L. L. J a c k s o n and Dr. J . E.
C a t l i n f o r t h e i r a d v ic e and guidance i n p re p a rin g t h i s t h e s i s .
A p p r e c i a t i o n i s a l s o d i r e c t e d t o w a r d Dr. R. E. Lund and Mr. R. L.
F r ie d r ic h f o r a s s i s t i n g i n th e s t a t i s t i c a l a n a ly s e s.
G ra titu d e i s
e q u a l l y e x t e n d e d t o Mark S p a u l d i n g , Rod L e a f d a l e and Dave Han f o r
a s s i s t i n g i n c o l l e c t i n g t h e d a t a and t o D iane Doede f o r t y p i n g t h e
V
m a n u sc rip t.
R ec o g n itio n i s a l s o d i r e c t e d t o Dr. David Cameron o f th e
Dana Ranch Company and Mr. Don S m ith and Mr. Gene H ensen o f t h e
M ontana S t a t e P r i s o n Ranch f o r s u p p l y i n g p a r t o f t h e a n i m a l s and
f a c i l i t i e s , used i n th e s e s t u d i e s .
I
w is h t o s i n c e r e l y
th a n k my p a r e n t s f o r t h e i r s u p p o r t and
g u i d a n c e and my w i f e ' s p a r e n t s , Mr. and Mrs. B i l l D e n n is , f o r t h e i r
e n c o u r a g e m e n t and s u p p o r t .
t h a n k my w i f e ,
L o rrie ,
F i n a l l y and m o st s i n c e r e l y , I w is h t o
f o r h e r e n c o u r a g e m e n t,
u n d e r s t a n d i n g and
a s s i s t a n c e i n a c c o m p l i s h i n g t h i s g o a l and o u r d a u g h t e r , D e n ic e , f o r
h e r charm and p a tie n c e w h ile h e r daddy was w r i t i n g h i s "phesus". .
TABLE OF CONTENTS
PAGE
V I T A ............................... . . ...................... ........................................................
ACKNOWLEDGEMENTS...................................
iii
TABLE OF CONTENTS.............................................................
LIST OF TABLES
. . . . . . . . . . . .
ii
.
.................. . . . . . . .
vi
LIST OF FIGURES . . .................... ....
v ii
ABSTRACT...................... .... . . ......................................................... ....
v iii
INTRODUCTION ................................................................................
REVIEW OF LITERATURE...............................................
iv
I
.
The Bovine E s tro u s Cycle . ..................................................................
D iv is io n s o f th e E s tro u s Cycle . . . . . . . . . . .
Hormonal C o n tro l o f th e E s tro u s Cycle
. . . . . . . .
C o n tro l o f E s tru s and O v u la tio n ............................................
Use o f P ro g e ste ro n e and P r o g e s t a g e n s ............................. .
Mechanism o f c o n t r o l ..........................
Types o f p ro g e s te r o n e .....................................................
Methods o f a d m i n i s t r a t i o n ........................................ .
Use . o f L u t e o l y t i c A g e n t s ........................................................
Mechanism o f l u t e o l y s i s ..........................
Types o f l u t e o l y t i c a g e n t s ............................................
Methods o f a d m i n i s t r a t i o n ............................................
Use o f P ro g estag en and L u t e o l y t i c Agent Com binations.
Mechanism o f c o n tr o l .........................................................
Methods o f a d m i n i s t r a t i o n ............................................
STATEMENT OF PROBLEM .......................................
M a te r ia ls and Methods ......................
. . . . . .
Animals ..................................
T r i a l s and T r e a t m e n t s ...................... . . ...................... .... .
T ria l- I
............................... .... . . : ...........................33
T r i a l 2 ..........................
D e te c tio n o f E s tru s and B reeding ........................................
S t a t i s t i c a l A n a l y s e s ..............................
. T r i a l I ..........................................................................
T r i a l 2 . . ................................... .... . ................... .. .
3
3
3
5
8
8
8
8
9
12
12
18
20
29
29
29
32
33
33
33
34
34
36
36
37
V
R e s u l t s ..........................
T rial I . . . .
......................................................... .
T ria l 2
. . . . .......................................
D is c u s sio n . . . . . .
............................................ . . . .
C onclusions ........................... . . . . . . . . .
..................
37
37
40
41
46
APPENDIX.............................................................
48
LITERATURE C I T E D ...................... ...................................... .... . ......................
60
vi
LIST OF TABLES
TABLE
1
2
3
4
5
6
7
PAGE
COW DISTRIBUTION BY HERD AND GROUP IN THREE HERDS OF
SUCKLED BEEF COWS RECEIVING TWO INJECTIONS OF PGFp
11 DAYS APART, .................................................... ...............................
38
CUMULATIVE Al PREGNANCY RATES BY DAY FOUR OF BREEDING
SEASON FOLLOWING UNTREATED CONTROL, LL-AI-E-80 AND
LL-AI-8 0 .......................................................................
53
PREGNANCY RATES OF COWS DETECTED IN ESTRUS DURING THE
FIRST FOUR DAYS OF DETECTION FOLLOWING UNTREATED
CONTROL, LL-AI-E-80 AND L L - A I - 8 0 ..................................................
PREGNANCY RATES OF COWS EITHER DETECTED IN ESTRUS ON
DAYS FIVE OR SIX OR NOT DETECTED DURING THE FIRST SIX
DAYS OF THE DETECTION PERIOD FOLLOWING LL-AI-E-80 AND
LL-AI-80 ............................................................. . . . . . . . .
54
55
ESTRUS IN TWO HERDS OF SUCKLED BEEF COWS RECEIVING
THE AI-L-AI-E BREEDING MANAGEMENT SYSTEM ................................
56
COMPARISON OF TWO BREEDING MANAGEMENT SYSTEMS USED
FOR 8 .5 DAYS OF ARTIFICIAL INSEMINATION.....................................
57
CUMULATIVE CALVING RATES AT VARIOUS STAGES OF THE
CALVING SEASON FOLLOWING TWO DIFFERENT BREEDING
MANAGEMENT SYSTEMS ............................................................. . . .
58
vii
LIST OF FIGURES
FIGURE
PAGE
1
Design o f b re e d in g management system s i n t r i a l I . , .
49
2
Design o f b re e d in g management system s i n t r i a l 2 . . .
50
3
P e rc e n t d i s t r i b u t i o n (means ± S. E .) o f e s t r u s
i n c o n t r o l s and cows r e c e i v i n g two i n j e c t i o n s o f
PGFga 11 days a p a r t i n th r e e h e rd s o f su ck led cows . .
51
P e rc e n t d i s t r i b u t i o n (means ± S. E . ) o f e s t r u s i n
t h r e e h e rd s o f s u c k le d b e e f cows r e c e i v i n g two
i n j e c t i o n s o f PGFga 11 days a p a r t
^
52
4
.
viii
ABSTRACT
T h re e h e r d s o f s u c k l e d b e e f cows (2 t o 10 y e a r s o l d ; n=656), a t
l e a s t 50 d a y s p o s t - p a r t u m , w e re u s e d i n two t r i a l s .
In t r i a l I 5
m em bers w i t h i n a h e r d w e re a s s i g n e d r a n d o m ly t o t h r e e g r o u p s : I)
c o n t r o l s , a r t i f i c i a l l y in s e m in a te d (Al) 12 h r a f t e r d e te c te d e s t r u s ;
2) cows r e c e i v i n g two i n j e c t i o n s o f 25 mg PGF2a ( f r e e a c id e q u iv a le n t)
11 d a y s a p a r t f o l l o w e d by Al 12 h r a f t e r d e t e c t e d e s t r u s u n t i l 80 h r
p o s t - t r e a t m e n t a t which tim e a l l members n o t y e t bred w ere in s e m in a te d
(LL-AI-E-80); and 3) cows r e c e i v i n g th e same PGF2a t r e a t m e n t a s LL-AIE -80 b u t in s e m in a te d o n ly a t 80 h r p o s t - t r e a t m e n t (appointm ent bred)
(LL-AI-80).
O b se rv a tio n s o f a l l groups f o r e s t r u s began im m e d ia te ly
a f t e r th e second PGF2 a i n j e c t i o n and w ere made tw ic e d a i l y f o r a 6-day
p e rio d . PGF2a- t r e a t e d cows, which were d e te c te d i n e s t r u s a f t e r day 4
w ere r e in s e m i n a te d u t i l i z i n g a g e n e t i c m arker to d e te r m in e s i r e o f
c a l f . Clean-up b u l l s w ere in tro d u c e d 12 h r a f t e r th e l a s t Al f o r th e
r e m a i n d e r o f a 5 0 -d a y b r e e d i n g s e a s o n . The r a t e o f d e t e c t e d e s t r u s
d u rin g th e f i r s t 4 days o f d e t e c t i o n was s i g n f i c a n t l y h ig h e r (P<.05)
i n t h e PGF2 - t r e a t e d cows t h a n i n t h e c o n t r o l s .
C u m u la tiv e Al
p re g n a n c y r a t e s (no. p r e g n a n t - no. i n g ro iip ) by day 4 o f b r e e d i n g
w ere:
12, 45 and 39? f o r c o n t r o l s , LL -A I-E -80 and L L -A I-8 0 ,
r e s p e c t i v e l y ; t h e p e r c e n t p r e g n a n t f o r LL -A I-E -80 and LL-A I-80 was
h i g h e r (P<.05) t h a n c o n t r o l s b u t d i d n o t d i f f e r (P>.05) fro m e ach
o t h e r . T o t a l p r e g n a n c y r a t e s o f cows d e t e c t e d (no. p r e g n a n t - no.
d e te c te d ) i n 4 days w ere n o t d i f f e r e n t (PX05) among groups. T h i r t y n i n e p e r c e n t o f t h e P G F ^ - t r e a t e d cow s t h a t w e re n o t d e t e c t e d i n
e s t r u s d u rin g th e 6 days p o s t - t r e a t m e n t w ere p reg n an t from th e 80 h r
b re e d in g ; none o f th o se d e te c te d on days 5 o r 6 were p re g n a n t to t h i s
b re e d in g . I n t r i a l 2, c o n t r o l s i n t r i a l I from two h e rd s (n=H4) were
i n j e c t e d w ith PGFga i f they had n o t been d e te c te d i n e s t r u s by day 4.5
and Al w as c o n t i n u e d f o r 4 more d a y s (A I-L -A I-E ).
R ep ro d u ctiv e
p e r f o r m a n c e o f t h i s g ro u p w a s.c o m p a re d w i t h t h a t o f t h e i r LL-A I-80
h erd m ates (n=109). F i r s t Al pregnancy r a t e s (no. p re g n a n t to 1 s t Al no. i n s e m i n a t e d ) w e re 68 and 47? (P ,.0 5 ) f o r A I-L -A I-E and L L -A I-80,
r e s p e c t i v e l y . T o ta l Al pregnancy r a t e s (no. p reg n an t t o 1 st Al r no.
i n g ro u p ) w e re 54 and 47? (P X 0 5 ) f o r A I-L -A I-E and L L -A I-80,
r e s p e c t i v e l y . C um ulative c a lv in g r a t e s (no. calv ed - no. i n group) by
day o f c a lv i n g seaso n f o r AI-L-AI-E and LL-AI-80, r e s p e c t i v e l y , were
day 10, 60 and 64?; day 3 8 , 75 and 89? (P<.05) and day 6 0 , 87 and 93?.
Time o f o n s e t o f e s t r u s up t o 96 h r a f t e r t h e d o u b le PGF2 a i n j e c t i o n
s y s t e m d i d n o t i n f l u e n c e p re g n a n c y r a t e t o an 80 h r b r e e d i n g . The
num ber o f Al c a l v e s p ro d u c e d i n e i t h e r t h e A I-L -A I-E o r LL-A I-80
system d id n o t d i f f e r , b u t more c a lv e s w ere born i n th e f i r s t 38 days
o f c a lv in g a f t e r th e LL-AI-80 p lu s c le a n -u p b u l l system th a n a f t e r th e
AI-L-AI-E p lu s c le a n -u p b u l l system.
INTRODUCTION
I n t e r e s t i n t h e d e v e lo p m e n t o f m e th o d s t o c o n t r o l t h e e s t r o u s
c y c l e o f t h e b o v in e h a s e v o lv e d fro m t h e p o s s i b i l i t y t h a t one c o u ld
m a n i p u l a t e a g ro u p o f f e m a l e s so th e y w ould be a t t h e same s t a g e o f
th e c y c le a t a s p e c i f i c tim e f o r b re e d in g .
This would a llo w p ro d u cers
t o u t i l i z e a r t i f i c i a l i n s e m i n a t i o n (A l) w i t h o u t n e e d in g a d d i t i o n a l
p astu re,
f a c i l i t i e s and tim e r e q u ir e d f o r d e t e c t i n g e s t r u s (h eat) i n a
group o f randomly c y c lin g fe m a le s f o r up to 25 days to g e t them bred.
A r t i f i c i a l in s e m in a ti o n i s an a p p e a lin g management to o l f o r improving
th e g e n e t i c p o t e n t i a l w i t h i n a h erd becau se i t p ro v id e s a c c e s s to
proven s i r e s which may no t o th e rw is e be a v a i l a b l e because o f economic
or g e o g ra p h ic a l c o n s t r a i n t s .
A r t i f i c i a l in s e m in a tio n has been w idely
a c c e p te d i n th e d a ir y i n d u s tr y and has r e s u l t e d i n e x te n s iv e g e n e tic
and p h e n o t y p i c p r o g r e s s i n i n d i v i d u a l m i l k p r o d u c t i o n .
B u t; d a i r y
p ro d u c e rs a r e n o t la b o re d w ith th e e x t r a tim e f o r h e a t d e t e c t i o n
because t h e i r p ro d u c tio n a n im a ls a r e alw ays a v a i l a b l e d u rin g normal
ro u tin e j
program s.
and Al can be i n c o r p o r a t e d r e a d i l y i n t o d a i r y b r e e d i n g
The u s e o f Al i n b r e e d i n g p r o g r a m s f o r d a i r y r e p l a c e m e n t
h e i f e r s and b e ef c a t t l e has n o t been a c c e p te d e a s i l y .
Yet, th e d e s i r e
o f p ro d u c e rs to u t i l i z e Al i n th e s e a n im a ls s t i l l e x i s t s .
Beef and d a ir y p ro d u c e rs i n th e U nited S t a t e s have been provided
t
I
th e o p p o r tu n ity to use e s tr o u s s y n c h r o n i z a t i o n i n b r e e d i n g p ro g ra m s
b e c a u s e o f t h e r e l e a s e o f p r o s t a g l a n d i n F2a^PGF2i^ bY t h e Food and
2
Drug A d m i n i s t r a t i o n (FDA).
T h is d ru g i s a p p ro v e d f o r u s e i n d a i r y
h e i f e r s and a l l c l a s s e s o f b e e f f e m a l e s .
P r o s t a g l a n d i n F2 a i s a
n a t u r a l l y o c c u rrin g su b sta n c e t h a t w i l l e f f e c t i v e l y
s h o rte n th e
e s t r o u s c y c le when a d m in is te r e d d u rin g th e l u t e a l phase.
T h erefo re,
t h e i n t e r v a l o f e s t r u s i n a g ro u p o f ra n d o m ly c y c l i n g cows may be
"sy n c h ro n iz e d " w ith
th e use o f t h i s
p ro d u c t.
B re ed in g
sy ste m s
recommended f o r use f o llo w in g a d m i n i s t r a t i o n o f PGF2^ in c lu d e :
I) Al
e i t h e r a f t e r d e te c te d e s t r u s or a t 80 h r f o llo w in g two i n j e c t i o n s ,
t o 12 d a y s a p a r t ;
in je c tio n ;
10
2) Al a f t e r d e t e c t e d e s t r u s f o l l o w i n g a s i n g l e
o r 3) n a t u r a l s e r v ic e .
To im plem ent th e use o f PGF2^ i n a b re e d in g management system f o r
r a n g e b e e f c a t t l e , i t i s n e c e s s a r y t o u n d e r s t a n d t h e b o v in e e s t r o u s
c y c le and th e mechanisms in v o lv e d i n i t s r e g u l a t i o n .
T h e re fo re , th e
f o ll o w i n g review o f l i t e r a t u r e w i l l be p re s e n te d t h a t d e s c r ib e s th e
e stro u s
c y c le in
t h e b o v in e and i t s
c o n tro llin g
m e c h a n ism s.
A l t e r n a t i v e methods f o r e s t r o u s s y n c h r o n iz a tio n w i l l a ls o be covered,
and th e ad v antages and d is a d v a n ta g e s o f th e s e methods w i l l be compared
w ith th o se t h a t i n c o r p o r a t e PGF2a.
REVIEW OF LITERATURE
The Bovine E s tro u s Cycle
Events o f th e m atu re fem ale bovine r e p r o d u c tiv e system occur i n a
s y m m e t r i c a l p a t t e r n c a l l e d t h e e s t r o u s c y c l e ( S o r e n s o n , 1979).
Thp
n o r m a l e s t r o u s c y c l e h a s an a v e r a g e l e n g t h o f 20 t o 21 d a y s and i s
u s u a ll y only i n t e r r u p t e d by pregnancy.
V arious c y c l i c changes occur
i n t h e r e p r o d u c t i v e o r g a n s o f t h e f e m a l e b o v in e d u r i n g t h e e s t r o u s
c y cle .
T hese c h a n g e s a r e r e f l e c t i v e
o f b o th m o r p h o l o g i c a l and
p h y s i o l o g i c a l e v e n t s t h a t o c c u r i n t h e o v a ry and r e p r o d u c t i v e t r a c t
and a r e
t h o u g h t to be r e g u l a t e d
n eu ro en d o crin e
by i n t e r a c t i o n s
b e tw ee n th e
( h y p o th a lm u s ) and r e p r o d u c t i v e e n d o c r i n e s y s t e m s
( p i t u i t a r y and o v a r i e s ) .
T hese i n t e r a c t i o n s a r e c h a r a c t e r i z e d by
f e e d b a c k c o n t r o l m e c h a n is m s i n v o l v i n g t h e h y p o t h a l m i c - p i t u i t a r y o v a r i a n a x i s ( s e e r e v i e w by N is w e n d e r
197*0.
The f o l l o w i n g
d i s c u s s i o n on d i v i s i o n s o f t h e e s t r o u s c y c l e a r e b a s e d on c y c l i c
o v a r ia n and b e h a v io r a l changes.
D iv is io n s o f th e E s tro u s C y cle.
F o u r m a jo r d i v i s i o n s o f t h e e s t r o u s c y c l e can be d i s c e r n e d and
th ey a r e :
I) e s t r u s ,
2) m e te s tr u s , 3) d i e s t r u s and 4) p r o e s tr u s .
E s tr u s marks th e b eginning o f th e c y c le and i s u s u a l l y d e sig n a te d
day 0.
Sorepson (1979) d e fin e d e s t r u s as th e p e rio d o f d e s i r e or tim e
when t h e f e m a l e w i l l a c c e p t t h e m a le f o r m a tin g .
fo r
a p p ro x im a te ly
16 h o u r s
b u t may r a n g e
fro m
T h is p e r i o d l a s t s
12 t o
24 h o u r s
k
(R o b in s o n ,
1977).
D u rin g t h i s p e r i o d a t l e a s t one o f t h e o v a r i e s
c o n t a i n s a l a r g e , m a t u r e f o l l i c l e w h ic h w i l l o v u l a t e a b o u t 10 h o u r s
a f t e r t h e end o f e s t r u s (R o b in s o n , 1977) o r 24 t o 32 h o u r s a f t e r t h e
o n s e t o f e s t r u s (Manns and Hafs ,
1976),
• M e te s tru s b e g in s im m e d ia te ly f o llo w in g e s t r u s and i s u s u a ll y two
d a y s i n l e n g t h (d a y s 2 - 4 ) .
The m a jo r o v a r i a n e v e n t o f m e t e s t r u s i s
o v u l a t i o n o r r e l e a s e o f t h e ova fro m t h e o v a r y .
The c e l l u l a r and
b i o c h e m i c a l e v e n t s i n t h e o v u l a t o r y p r o c e s s h av e b e e n r e v i e w e d by
Espey (1974) and w i l l n o t be d i s c u s s e d i n t h i s t e x t .
o v u la tio n ,
F o llo w in g
th e p r o l i f e r a t i n g g ra n u lo s a and th e c a i n t e r n a c e l l s o f th e
r u p tu r e d f o l l i c l e d i f f e r e n t i a t e i n t o l u t e a l c e l l s t o form th e corpus
h e m o r r h a g ic u m .
T h i s s t r u c t u r e m a t u r e s t o e v e n t u a l l y fo rm a c o r p u s
luteum (CL) i n th e n e x t s ta g e .
D ie s tr u s i s c h a r a c t e r i z e d by th e p re sen c e of th e d e f i n i t i v e CL i n
th e
o v ary.
L e n g th
of
d ie stru s
a p p r o x i m a t e l y 11 d a y s (d a y s 5 - 1 6 ) .
is
v a ria b le
but
u su a lly
la sts
I f f e r t i l i z a t i o n and c o n c e p t i o n
fr o m m a t i n g d u r i n g e s t r u s h av e n o t o c c u r r e d r e g r e s s i o n o f t h e CL
( I u t e o l y s i s ) i s i n i t i a t e d on day 16 ( S t a b e n f e l d t . a t sJL., 1978).
has
been
n o te d
th a t
fo llic u la r
g r o w th
occurs
d u rin g
It
d ie stru s
( S t a b e n f e l d t e t . a l . r 1980), h o w e v er t h e s e f o l l i c l e s do n o t u s u a l l y
m atu re
b u t u n d e rg o a t r e s i a
(fo llic u la r
d e a th ).
It
may be t h a t
f o l l i c u l a r grow th d u rin g t h i s p e rio d i s one f a c t o r i n th e i n i t i a t i o n
o f l u t e o l y s i s.
5
I f l u t e o l y s i s i s i n i t i a t e d d i e s t r u s ends and p r o e s t r u s (days 1720) b eg in s.
During t h i s p e rio d l u t e o l y s i s i s com pleted and a corpus
a l b i c a n s i s th e r e s u l t o f t h i s p ro c e ss.
ta k e s p la c e d u rin g p r o e s t r u s ,
becom es
d e v e lo p e d
(S ta b e n fe ld t
fo r
E x ten siv e f o l l i c u l a r growth
and th e f o l l i c l e ( s ) d e s ti n e d to o v u la te
o v u la tio n
a fte r
th e
subsequent e s tru s
» 1978).
Hormonal C o n tro l o f th e E s tro u s C ycle.
The m a jo r h o rm o n e s i n v o l v e d i n r e g u l a t i o n o f t h e e s t r o u s c y c l e
are:
f o l l i c l e s t i m u l a t i n g hormone (FSH) and l u t e i n i z i n g hormone (LH)
from th e a n t e r i o r p i t u i t a r y ; p ro g e s te ro n e (Plf) from th e CL; e s tr o g e n s
( m a i n l y e s t r a d i o l - 1 7 g; Eg) fro m o v a r i a n f o l l i c l e s ; and g o n a d o t r o p i n
r e l e a s i n g horm one (GnRH) fro m t h e h y p o th a lm u s .
P r o s t a g l a n d i n Fga,
a l t h o u g h n o t c o n s i d e r e d a horm one p e r s e .
a n o th e r im p o rta n t
is
e f f e c t o r t h a t i s produced by th e endometrium o f th e u te r u s .
The p i t u i t a r y g o n a d o tro p in s, FSH and LH, a re n e c e ssa ry f o r grow th
and m a tu r a tio n o f th e f o l l i c l e and o v u la tio n (Sorenson, 1979).
Plasma
c o n c e n t r a t i o n p a t t e r n s o f t h e g o n a d o t r o p i n s show low t o n i c l e v e l s
t h r o u g h m o st o f t h e c y c l e u n t i l a f t e r l u t e o l y s i s .
T h e re a r e s l i g h t
i n c r e a s e s , m a i n l y on day 10, w h ic h a r e t h o u g h t t o be i n v o l v e d i n
m id cy cle f o l l i c u l a r grow th.
These i n c r e a s e s a r e s h o r t i n d u r a tio n and
c o n c e n tr a tio n s im m e d ia te ly r e t u r n t o b a s a l l e v e l s (R o b in s o n , 1977).
During p r o e s t r u s plasm a FSH c o n c e n tr a tio n s beg in t o r i s e s h o r t l y a f t e r
6
l u t e o l y s i s t o peak l e v e l s a t or n ear th e o n s e t o f e s t r u s th e n d e c lin e
r a p i d l y ( H a c k e t t and H a fs , I 969).
P la s m a LH c o n c e n t r a t i o n s " s u r g e ”
fro m 2 -3 n g /m l up t o 10 -5 0 n g /m l n e a r t h e o n s e t o f e s t r u s , r e m a i n
e l e v a t e d f o r 8 -1 0 h o u r s , t h e n r a p i d l y d e c l i n e ( S t a b e n f e l d t e t a l . f
1978).
The LH s u rg e i s a m ajor s tim u lu s f o r p v u la tio n (Espey,
1974),
and low b a s a l c o n c e n t r a t i o n s o f LH t h a t f o l l o w i n m e t e s t r u s a r e
n e c e s s a ry f o r th e f o r m a tio n and m aintenance of th e CL (Hansel
al« ,
1973).
Plasma c o n c e n tr a tio n s o f th e ovarian, hormones, P11 and e s tr o g e n s ,
f l u c t u a t e r e l a t i v e to th e a c t i v i t y of t h e i r r e s p e c tiv e s e c r e to r y
o v a ria n s tr u c tu r e .
P r o g e s t e r o n e , s e c r e t e d p r i m a r i l y by t h e c o r p u s
lu teu m , r i s e s from <1 ng/m l to 6-7 ng/m l between days 5 and 10 d u rin g
d i e s t r u s (S m ith && a t . , I 975) and r e m a i n e l e v a t e d u n t i l day 16 when
l u t e o l y s i s i s i n i t i a t e d (C atchpole,
of p ro g e ste ro n e
is
1977).
One of th e m ajor f u n c tio n s
p h y s io lo g ic a l p r e p a r a tio n o f th e u te ru s fo r
p r e g n a n c y , i f i t o c c u r s ( S o r e n s o n , 1979).
P la s m a Eg c o n c e n t r a t i o n s
i n c r e a s e d u r i n g d i e s t r u s when f o l l i c u l a r g r o w th i s a c t i v a t e ^ b u t
s u b s i d e a s a t r e s i a o c c u r s (S m ith e t a l . . I 975).
The m a jo r p e ak o f Eg
c o n c e n tr a tio n s (7-11 pg/m l) o c cu rs about one day p r i o r to e s t r u s and
i s th e m ajor s tim u lu s f o r th e p re o v u la to ry LH su rg e (C henault .§£.
1975) and in d u c in g b e h a v io r a l e s t r u s (Ganong, 1977).
I n j e c t i o n s o f Eg
r e s u l t e d in in d u c in g b e h a v io ra l e s tr u s in o v a rie c to m iz e d h e i f e r s
( G a r r i c k and S h e l t o n ,
1969) and a p r e o v u l a t o r y - l i k e LH s u r g e i n
7
p r e p u b e r ta l h e i f e r s ( S c h il lo s L sJL.» 1981).
E stro g e n s produced d u rin g
d i e s t r u s may i n i t i a t e t h e r e l e a s e o f PGFg^ fro m t h e u t e r u s t o c a u s e
l u t e o l y s i s (Goldberg and Hamwell9 1975).
R e l e a s e p a t t e r n s o f PGFg^, i n t o
th e
u te rin e
v e i n h ave b e e n ,
d e t e r m i n e d by m e a s u r in g p la s m a c o n c e n t r a t i o n s o f 13»14 - d ih y d r o - 15Iceto-PGFga , t h e m a jo r m e t a b o l i t e o f PGFga ( P e t e r s o n s i .
1975).
W e ll d e f i n e d s u r g e s o f t h i s PGFga m e t a b o l i t e o f a b o u t s i x h o u r s
d u r a t i o n o ccu r b e g in n in g on day 16, w ith t o t a l l u t e o l y s i s o c c u r rin g i n
about 36 ho u rs ( S ta b e n f e ld t .§£ a l . ,
1980).
The Iiypotha1Imus produces and r e l e a s e s GnRH w h ic h r e g u l a t e s t h e
re le a se
of
b o th
FSH and LH fro m
th e
a n te rio r
p itu ita ry .
The
hypothalam us i s thought to be th e r e g u l a t o r y c e n te r both f o r t o n ic and
e p i s o d i c r e l e a s e o f t h e g o n a d o t r o p i n s (Lamming
s i.,
1979).
The
t o n i c and e p i s o d i c r e l e a s e c e n t e r s a r e c o n t r o l l e d by n e g a t i v e f e e d
b a ck e f f e c t s o f P^ and Eg.
Thus, a s t h e p la s m a c o n c e n t r a t i o n s o f
t h e s e o v a r i a n h o rm o n e s i n c r e a s e ,
re su lts.
an i n h i b i t i o n
o f GnRH r e l e a s e
Y et, i n t h e ewe w i t h r e s p e c t t o LH r e l e a s e , Plt a c t s on t h e
hypothalm us to d e c re a s e th e frequency o f GnRH d is c h a rg e s w h ile Eg a c t s
i n th e p i t u i t a r y t o d e c re a se i t s re sp o n se t o each GnRH p u ls e (Goodman
and K a r s c h ,
1980).
s i t u a t i o n i n th e cow.
T h ese a u t h o r s s u g g e s t e d t h a t t h i s i s a l s o t h e
The p re o v u la to ry LH surge i s t r i g g e r e d through
a p o s i t i v e feedback o f Eg a c t i n g p r i m a r i l y on th e s u rg e c e n te r i n th e
hypothalm us and s e c o n d a r ily a t th e l e v e l o f th e p i t u i t a r y
(Lamming s i
8
&L,
1979).
W ith
th e
b a sic
u n d e rsta n d in g
of
th e
m o rp h o lo g ic a l
and
p h y s io lo g ic a l changes t h a t occur d u rin g th e bovine e s t r o u s c y cle and
th e n eu ro en d o crin e and e n d o c rin e hormones t h a t r e g u l a t e th e s e changes
i t i s p o s s i b l e to conclude t h a t one m ight m a n ip u la te th e e s t r o u s c y c le
h o r m o n a l l y so a s t o c o n t r o l t h e t i m e o f e s t r u s and o v u l a t i o n i n t h e
fem ale bovine.
C o n tro l o f E s tru s and O v u latio n
Use o f P ro g e s te ro n e and P ro g e sta g e n s.
M echanism o f c o n t r o l .
I t i s h y p o th e size d t h a t p ro g e s te ro n e
i n h i b i t s th e r e l e a s e o f GnRH from th e hypothalm us which r e g u l a t e s th e
r e l e a s e o f g o n a d o tro p in s from th e p i t u i t a r y .
T h e re fo re ,
when plasma
p r o g e s t e r o n e l e v e l s a r e h i g h , g r o w th and m a t u r a t i o n o f f o l l i c l e s ,
e s t r u s and o v u l a t i o n a r e i n h i b i t e d .
Thus, by t r e a t i n g a g ro u p o f
ra n d o m ly c y c l i n g b o v in e f e m a l e s w i t h e x o g e n o u s p r o g e s t e r o n e o r
p r o g e s t a g e n s f o r a t l e a s t 16 d a y s ( t h e l e n g t h o f t h e c y c l e th r o u g h
d ie stru s)
a ll
a n i m a l s w o u ld
be i n
p ro e stru s
when t r e a t m e n t
is
withdrawn and sy n ch ro n ized e s t r u s and o v u la tio n would fo llo w .
Tvoes o f p ro g e s te ro n e .
Suspensions o f Plf i n corn o i l were f i r s t
used i n p ro g e s te ro n e tr e a tm e n t regim ens.
O ra lly a c t i v e p ro g e stag e n s
w e re d e v e lo p e d i n w ork on human c o n t r a c e p t i o n and t h i s g e n e r a t e d
i n t e r e s t in fe e d in g th e se p ro g e stag e n s to c a t t l e .
T h ese compounds
9
in c lu d e :
6- m e t h y l - I 7 -a c e to x y p r o g e s te rn e (MAP), 6 -c h lo ro -6 -d e h y d ro -1 7 -
a c e to x y p ro g e s te ro n e (CAP), dihydroxy p r o g e s t e r o n e a c e t o p h e n i d e (DHPA)
and m e le n g e s tro l a c e t a t e (MGA) and can be mixed w ith fe e d c o n c e n tr a te s
or w a te r fo r a d m in is tr a tio n .
O th e r t y p e s o f p r o g e s t a g e n s h ave b e en
developed arid in c o r p o r a te d i n t o i n t r a v a g i n a l d e v ic e s and subcutaneous
im p la n ts .
These in c lu d e :
p r o g e s t e r o n e (C ro n o lo n e® ,
(N ile v a r® ,
SC -5914)
17 a - a c e t o x y - 9 - f I u r o - 1 1 S - h y d r o x y -
S C -9 8 8 0 ),
and
I 7 a -e th y l-1 9 -n o rte sto ste ro n e
17 a - a c e t o x y - 1 I S - I 9 - n o r p r o g e s t e r o n e
( N o r g e s t a m e t ^ SC-21009).
Methods o f a d m i n i s t r a t i o n .
to
D aily i n j e c t i o n s o f 50 mg P^ f o r 13
17 d a y s o r a s i n g l e i n j e c t i o n o f 560 mg Pjj a r e
e ffe c tiv e
in
s u p p re s s in g h e a t and p re v e n tin g o v u l a t i o n i n bovine fe m a le s ( C h r is tia n
and C a s i d a , 1948; W i l l e t t , 1950; O l b e r g s l s l . , 1951; T r i m b e r g e r and
H ansel,
1955; N e llo r and Cole,
1956).
S tu d ie s on f e r t i l i t y i n bovine
fe m a le s in s e m in a te d a t th e e s t r u s a f t e r th e s e tr e a tm e n ts showed low er
t h a n n o r m a l f e r t i l i t y ( W i l l e t t , 1950, T r i m b e r g e r and H a n s e l, 1955;
N e llo r and Cole,
1956).
But,
f e r t i l i t y a t the second p o s t - t r e a t m e n t
e s t r u s was n o r m a l (H a n s e l s i s i . t 1959; O sla n d s l a l . »
1970).
R aysl
S i . (1961) s t u d i e d t h e p h y s i o l o g i c a l and m o r p h o l o g i c a l e f f e c t s o f
exogenous P^ on th e bovine fem a le r e p r o d u c tiv e t r a c t .
in c lu d e d :
lo w e re d
p itu ita ry
FSH and LH p o t e n c i e s ;
These e f f e c t s
sm aller
CL
d ia m e te r s ; and lo w e r c e l l h e ig h ts o f g la n d u la r e n d o m e tria l e p ith e liu m .
10
'f
It
/
was s u g g e s t e d
th a t
f e r t i l i t y a fte r
■
th e se e f f e c t s
c o n tr ib u te d to th e lo w ered
tr e a tm e n t.
The use o f more s t a b l e o r a l l y - a c t i v e p ro g e stag e n s was s tu d ie d as
an a l t e r n a t e r o u te o f a d m i n i s t e r i n g
to bovine fe m a les.
S u c c e s s fu l
i n h i b i t i o n o f e s t r u s and o v u la tio n was r e p o r te d a f t e r fe e d in g MAP f o r
11 t o 20 d a y s (H a n s e l and M alv en , I9 6 0 ; H a n s e l S ^ a X , , 1961; C o l l i n s
.§£. s i . ,
1961; Nelms and Combs, 1961; Zimbelman, 1961; Anderson e t a l . ,
1962; Fahning e t a l . f 1966).
A more p o te n t p ro g e stag e n , CAP, was l e s s
e f f e c t i v e i n sy n c h ro n iz in g e s t r u s when fe d f o r th e same le n g th o f tim e
(Van B la k e £ £ s i . ,
1961; H a n s e l s i aJL., I 966; Wagner
s i . . » 1968).
B u t, s u c c e s s f u l s y n c h r o n i z a t i o n o f e s t r u s o c cu rred a f t e r fe e d in g an
even more p o te n t p ro g e stag e n , MGA (Zimbelman and Sm ith,
1966; Roussel
and B e a t t y , I 969; R o u s s e l s i . s i . » I 969; H i l l s i s i . , 1971).
A lso DHPA
e f f e c t i v e l y sy n ch ro n ized e s t r u s i n b e ef h e i f e r s when fe d f o r 20 days
(W ilb a n k s i S i.»
1967).
F e r t i l i t y to in s e m in a tio n s a t th e e s tr u s
a f t e r c e s s a t i o n o f t r e a t m e n t w i t h t h e s e p r o g e s t a g e n s was a lw a y s a t
l e a s t 10 to 15 p e rc e n t lo w e r th a n t h a t i n u n tr e a te d c o n t r o l s (Hansel
e t s i . > 1966; W iltb a n k s i S i . > 1967, R o u s s e l s i S i . ,
S i.,
1969» H i l l s i
1971).
Due
to
th e
in a b ility
p ro g e sta g e n in ta k e
p ro g e s ta g e n s ,
a n o th e r
to
p re c ise ly
by i n d i v i d u a l s
c o n tr o l
th e
amount
of
in a group o f a n im a ls fe d
i n t r a v a g i n a l and subcutaneous im p la n ts w ere s tu d ie d as
method
of
ad m in istra tio n .
C ronolone-im pregnated
sponge
11
p e s s a r i e s p l a c e d i n t r a v a g i n a l l y i n b o v in e f e m a l e s f o r 18 o r 19 d a y s
w e re e f f e c t i v e i n s y n c h r o n i z i n g e s t r u s and o v u l a t i o n ( G a r r i c k and
S h e lto n ,
1967;
S h im iz u JLksJL.,
1967;
W i s h a r t and H o sk in ,
1968).
R e t e n t i o n o f t h e s e p e s s a r i e s t h r o u g h t h e t r e a t m e n t p e r i o d was l e s s
th a n s a t i s f a c t o r y , bu t t h i s was rem edied by ap p ly in g a n t i b i o t i c s p r i o r
to i n s e r t i o n
(S c a n lo n e t a l . .
1972).
R o ch e ( 1 9 7 6 a ) r e p o r t e d
s a t i s f a c t o r y r e t e n t i o n and s y n c h r o n iz a tio n o f e s t r u s i n bovine fe m a les
re c eiv in g a s i l a s t i c c o il p r o g e s te r o n e - r e le a s in g - in tr a v a g in a l- d e y ic e
(PRID) f o r 12 d a y s .
S u c c e s s f u l s y n c h r o n i z a t i o n o f e s t r u s i n cows
r e c e i v i n g e i t h e r MAP-impregnated subcutaneous ru b b e r im p la n ts f o r 22
t o 64 d a y s o r p l a s t i c s u b c u t a n e o u s N i l e v a r i m p l a n t s f o r 16 d a y s was
r e p o r t e d by D z u i k s i s jI . (1966) and C u r l s i a l . (1 9 6 8 ), r e s p e c t i v e l y .
Although th e s e methods o f a d m i n i s t r a t i o n d id improve th e r e g u l a t i o n o f
p ro g e s te ro n e or p ro g e stag e n in t a k e th e problem o f low f e r t i l i t y a t th e
e s t r u s a f t e r removal o f th e so u rce s t i l l p e r s i s t e d .
Since p ro g e s te r o n e and p r o g e s ta g e n t r e a t m e n t s w e re u n d e s i r a b l e
because o f low f e r t i l i t y o th e r methods t o c o n t r o l e s t r u s and o v u la tio n
were needed.
With th e developm ent o f a p a r t i a l u n d e rs ta n d in g o f th e
mechanism o f l u t e o l y s i s d u rin g th e e s t r o u s c y c le , th e use o f exogenous
lu te o ly tic
of co n tro l
a g e n ts has been s tu d ie d
a s an a l t e r n a t i v e
m e th o d
12
Use o f L u t e o l v t i c A gentsMechanism o f l u t e o l v s i s .
I t h as been e s t a b l i s h e d t h a t th e u te r u s
i s n e c e s s a r y f o r i n i t i a t i n g l u t e o l y s i s i n t h e b o v in e .
W iltb a n k and
C a s id a (1956) r e p o r t e d t h a t r e m o v a l o f t h e u t e r u s ( h y s t e r e c t o m y )
p r o l o n g e d n o rm a l CL f u n c t i o n i n t h e n o n p r e g n a n t cow.
From t h i s and
s i m i l a r w ork i n o t h e r mammals i t w as h y p o t h e s i z e d t h a t t h e u t e r u s
produced a s u b s ta n c e t h a t caused r e g e s s i o n o f th e CL.
Through th e use
o f a u t o - t r a n s p l a n t s o f o v a r i e s and u t e r i i n ew es (M cC racken e t a l . f
1972) and p a r t i a l h y s te r e c to m ie s i n cows and ewes (Cumming,
1975) i t
was e s t a b l i s h e d t h a t t h e e f f e c t o f t h e u t e r u s on t h e CL i s l o c a l i n
n a tu re
and r e q u i r e d
th e
u te rin e
ho rn i p s i l a t e r a l
to
th e
o v a ry
c o n ta in in g th e CL. .
P h a r is s and Wyngarden (1969) s u g g e ste d t h a t a p r o s ta g la n d i n might
be th e u te rin e -p ro d u c e d s u b s ta n c e t h a t caused l u t e o l y s i s .
They showed
t h a t p r o s t a g l a n d i n F2 a i s fo u n d i n a b u n d a n c e i n t h e u t e r u s and h ig h
doses a d m in iste re d
to
ra ts
(I
s h o r te n in g o f pseudopregnancy.
th a t
m g /k g /d a y )
caused
a
s ig n ific a n t
B abcock (1966) had f i r s t s u g g e s t e d
p r o s ta g la n d i n s m ight be l u t e o l y t i c and t h i s was c u lm in a ted by
r e s e a r c h done by M cCracken e t a l . (1972) i n t h e ewe ( a s r e v i e w e d by
Hansel
a l,,
1973).
T h eir c o n c lu s io n was based on:
I)
in fu sio n of
PGF2aBt a l e v e l o f 25 u g / h r i n t o t h e a r t e r i a l s u p p ly o f t h e a u t o t r . a n s p l a n t e d o v a r y ( i n t h e n e ck a r e a ) c a u s e d a r a p i d
d e c lin e
in
p ro g e s te r o n e s e c r e t i o n , fo llo w e d by a r i s e i n e s t r a d i o l s e c r e t i o n and
13
a p e ak i n LH s e c r e t i o n w h ic h o c c u r r e d s h o r t l y a f t e r t h e o n s e t o f
e stru s;
2)
th e l e v e l o f PGFga i n th e u t e r i n e venous blood o f th e ewe
i n c r e a s e s a t a b o u t t h e sam e t i m e t h e CL b e g i n s t o r e g r e s s ;
and 3)
p e ak l e v e l s o f PGF2a o f 42 n g /m l o f u t e r i n e v e i n p la s m a h av e b e en
measured.
Assuming a u t e r i n e v e in blood flow o f 15 m l/m in, i t may be
c a lc u la te d
t h a t t h e u t e r u s c a n r e l e a s e up t o 25 u g / h r o f PGF2 a .
I n f u s i o n o f PGF2a a t t h i s r a t e i n t o th e u t e r i n e v e in has been shown to
c a u s e p r e m a t u r e l u t e o l y s i s and a d e c l i n e i n p la s m a p r o g e s t e r o n e i n
t h r e e i n t a c t ew es t r e a t e d on d a y s 6 , 10 and 14 ( l u t e a l p h a s e ) o f t h e
c y cle .
H ansel
( I 973) r e f u t e d t h i s c o n c l u s i o n i n r e f e r e n c e t o
th e bovine by c i t i n g evid en ce t h a t PGF2a and o th e r p r o s ta g la n d i n s were
l u t e o t r o p i c when added to bovine l u t e a l t i s s u e i n v i t r o .
W ith
th e
id e a
th a t
PGF2a c o u ld
be t h e
endogenous u t e r i n e
lu te o ly sin ,
a t t e m p t s to ind u ce l u t e o l y s i s w ith exogenous PGF2a were
perform ed.
S u c c e s s f u l CL r e g r e s s i o n w as a t t a i n e d i n c a t t l e u s i n g
i n t r a - u t e r i n e i n f u s i o n s ( L i e h r n l. a l . ,
L a m o h d n in l.,
1973; L o u i s n l n l . ,
1972; Rowson Mi.
1972;
1974), s u b c u t a n e o u s i n j e c t i o n s
( L a u d e r d a l e , 1972) and. i n t r a m u s c u l a r i n j e c t i o n s ( S t e l l f i u g e t a l . f
197 5 ).
S u p p o r t f o r t h e c o n c l u s i o n t h a t PGF2^ i s t h e e n d o g en o u s
u t e r i n e l u t e o l y s i n i n th e bovine has been provided by measurement o f
t h i s s u b sta n c e i n th e u t e r i n e endometrium,
a rte ry .
u t e r i n e v e in and o v a ria n
Shemish and Hansel (1975) and Lamothe s i a l .
(1977) r e p o r te d
c y c l i c v a r i a t i o n s i n u t e r i n e s e c r e t i o n s o f PGF2 a w ith h ig h e s t v a lu e s
14
b e in g ob serv ed d u rin g l u t e a l r e g r e s s io n .
LaVoie sfc aJU (1975) f u r t h e r
s u p p o rte d t h i s c o n c lu s io n by d e m o n s tra tin g t h a t CL r e g r e s s i o n could be
induced i n t o t a l l y h y s te r e c to m iz e d cows w ith s i n g l e i n j e c t i o n s o f 30
mg PGF2ct.
I t h a s b e e n d e t e r m i n e d t h a t a l o c a l u t e r o - o v a r i a n p a th w a y i s
in v o lv e d i n u t e r i n e induced l u t e o l y s i s i n th e bovine (as review ed by
G in th e r,
1974).
The n a tu r e o f t h i s pathway has been h y p o th e size d to
in v o lv e th e c lo s e a p p o s itio n o f th e u te r o - o v a r ia n v e in w ith th e
o v a r ia n a r t e r y .
This a llo w s f o r a " co u n ter c u r r e n t" mechanism where
by PGF2a from u t e r i n e venous blood i s passed through th e w a ll o f th e
u t e r o - o v a r i a n v e i n i n t o t h e o v a r i a n b lo o d s u p p l y .
tra n s fe r
to o ccur w ith o u t e n t e r i n g
th e
T h is a llo w s th e
sy ste m ic
c irc u la tio n .
McCracken s t . a l , (1972) r e p o r te d t h a t i n ewes, t r i t i u m l a b e l l e d PGFg01
in fu sio n in to
th e
u te ro -o v a ria n
v e i n was f o l l o w e d
by a h i g h e r
c o n c e n t r a t i o n o f l a b e l l e d PGF2oi b e i n g d e t e c t e d i n t h e i p s i l a t e r a l
o v a r ia n a r t e r y th a n t h a t d e te c te d i n th e i l i a c a r t e r y .
This s u p p o rts
th e c o u n te r c u r r e n t exchange concept.
F u r th e r a tte m p ts t o su p p o rt t h i s concept i n r e f e r e n c e t o th e cow
have
been
q u e stio n e d
due
to
fa ilu re
to
observe
in c re a s e d
c o n c e n t r a t i o n s o f PGF201 i n o v a r i a n a r t e r i a l b lo o d a t t i m e s when
c o n c e n tr a tio n s o f PGF2^ i n u t e r i n e venous plasm a were c l e a r l y e le v a te d
( I n s k e e p and M urdoch, 1980).
H a n se l e £ a l . (1976) p o i n t e d o u t t h a t
p r o b le m s i n m e a s u r i n g p la s m a PGF201 a r e e n c o u n t e r e d due t o w id e
15
d i s t r i b u t i o n o f p r o s t a g l a n d i n s y n t h e t a s e i n many t i s s u e s .
w o rk ers
c ite d
e v id e n c e
th a t
These
m e c h a n ic a l m a n ip u la tio n o f th e
r e p r o d u c tiv e t r a c t and even s a l i n e i n j e c t i o n s i n t o o v a r ie s can e l e v a t e
PGFgot c o n c e n t r a t i o n s .
To f u r t h e r
confound
th e
p ro b le m
of
d e t e r m i n a t i o n o f PGFga I n b lo o d i t w as n o t e d t h a t b lo o d p l a t e l e t s
p r o d u c e p r o s t a g l a n d i n s i n t h e c l o t t i n g p r o c e s s a l t h o u g h t h i s can be
re m e d ied
by r a p i d
w ith d ra w a l.
c e n trifu g a tio n
and
free zin g
fo llo w in g
b lo o d
Y e t, i t i s a p p a r e n t t h a t t h e s i g n i f i c a n c e o f p la s m a
p r o s t a g l a n d i n c o n c e n tr a tio n s i s d e b a ta b le .
I t h a s b e e n h y p o t h e s i z e d t h a t p r o g e s t e r o n e and e s t r o g e n p l a y a
key r o l e i n s t i m u l a t i n g PGFga s y n t h e s i s i n th e u te r u s ,
S t a b e n f e ld t e t
a l . ( 1980) r e v i e w e d e v i d e n c e t h a t e s t r o g e n s a r e n e c e s s a r y f o r t h e
s y n t h e s i s o f enzym es n e e d e d t o e i t h e r h y d r o l i z e t h e p h o s p h o l i p i d
s o u rc e
of
a ra c h id o n ic a c id ,
the p r e c u r s o r o f PGFga ,
PGFga .
A ls o , i t was h y p o t h e s i z e d t h a t
or s y n th e s iz e
exposure o f th e u te ru s to
p r o g e s t e r o n e was n e c e s s a r y f o r d e v e l o p i n g t h e l i p i d d r o p l e t s w h ic h
c o n ta in th e p h o sp h o lip id s.
T h is my h e l p
t o e x p l a i n why s i n g l e
i n j e c t i o n s o f PGFga a r e n o t e f f e c t i v e on C ycling cows t h a t a r e i n the
m e t e s t r u s s t a g e (Rowson jg£ a l . . ,
u te ru s has not re c e iv e d
H ow ever,
B e a l afc. S i .
1972; H e n r ic k s a l a l . *
a m p le e x p o s u r e to
(1980)
re p o rte d
P^ d u r i n g
su ccessfu l
1974).
The
m e te stru s.
in h ib itio n
of
p ro g e s te r o n e s e c r e t i o n by CL i n H o ls te i n h e i f e r s t h a t w ere i n days 3
and 4 o f t h e i r c y c le w ith tw ic e d a i l y in tr a m u s c u la r i n j e c t i o n s o f 25
16
mg PGF201.
The p r e c i s e m ech an ism by w h ic h PGF2a c a u s e s d e m i s e . o f l u t e a l
t i s s u e h a s no t been r e p o r te d u n e q u iv o c a lly .
Many h y p o th eses have been
p r e s e n te d but most o f th e s e have been r e f u t e d .
H e n d e rs o n and M cN atty ( 1975) h a v e h y p o t h e s i z e d a p l a u s i b l e
b i o c h e m i c a l m ech an ism o f PGF2a- I n d u c e d l u t e o l y s i s .
T hese w o r k e r s
c i t e d ev id en ce t h a t e x p la in e d th e mechanism o f p ro g e s te ro n e p ro d u c tio n
o f th e l u t e a l c e l l .
The p la s m a mem brane o f l u t e a l c e l l s c o n t a i n
s p e c i f i c b i n d i n g s i t e s f o r LH w h ic h , upon r e c e p t i o n o f LH, a c t i v a t e
th e
adenyl
c y c la se
s t e r i o d o g e n i c en zy m e s.
sy ste m
n ecessary
fo r
a c tiv a tio n
of
th e
F o l l o w i n g t h e p r e o v u l a t o r y LH s u r g e , t h e s e
r e c e p t o r s i t e s become a c t i v a t e d ; t h i s r e s u l t s i n m o r p h o l o g i c a l and
fu n c tio n a l
(p ro g este ro n e
p ro d u c tio n ) i u t e i n i z a t i o n .
The p la s m a
membrane o f l u t e a l c e l l s a l s o c o n t a i n s p e c i f i c b i n d i n g s i t e s f o r
PGF2 a ( K im b a ll and L a u d e r d a l e ,
1975) b u t when LH h a s f i l l e d
membrane r e c e p t o r s th e s e s i t e s a r e masked f o r PGF2a r e c e p tio n .
may a l s o
PGF2a
e x p la in
why t h e e a r l y
(H e n d e rs o n and M c N a tty ,
1.977).
r e c e p t i o n o f PGF2a by t h e m em brane.
in c re a sin g
This
CL ( m e t e s t r u s ) i s r e f r a c t o r y t o
As t h e
d i s s o c i a t i o n o f LH from i t s r e c e p t o r s o ccu rs.
to w a r d
its
CL a g e s ,
g radual
This opens th e way f o r
Thus, a s t h e b a l a n c e s h i f t s
PGF2a c o n c e n t r a t i o n s
o v e r LH c o n c e n t r a t i o n s ,
a c t i v a t i o n o f adenyl c y c la s e i s i n h i b i t e d w i t h i n th e membrane. . This
r e s u l t s i n d e c l i n i n g p ro g e s te ro n e s e c r e t i o n and su b sequent demise o f
17
t h e CL.
I n o p p o s i t i o n t o t h e h y p o t h e s i s t h a t LH s a t u r a t i o n o f l u t e a l
re c e p to rs
p re v e n te d
PGF2a - i n d u c e d
lu te o ly sis
in
th e
e a rly
CL,
G o n z a le z - M e n c io a l a l . ( 1977) r e p o r t e d t h e f a i l u r e o f ex o g en o u s LH,
g iv e n
to h e i f e r s
on d a y s
10 t o
12 o f
th e ir
c y cle ,
l u t e o l y s i s when fo llo w e d fo u r ho u rs l a t e r by 25 mg PGF2 a .
to
p revent
I t may be
p o s s i b l e t h a t t h e l o s s o f b i n d i n g c a p a c i t y (H ic h e n s g£ S i . , I 974) by
days
th e
10
to
PGF2a
12
p re v e n ted
th e
exogenous
LH from
in h ib itin g
effect.
O ther p o s s i b l e proposed mechanisms in v o lv e th e v a s c u l a t u r e o f th e
CL c o n t a i n i n g o v a r y .
P r o s t a g l a n d i n F 2a c o n t r a c t s a l l f o u r k i n d s o f
smooth m uscle and i t s
v e n o c o n s t r i c t i v e a c t i o n may induce hypoxia i n
t h e o v a r y , w h ic h i n t u r n may l e a d t o l u t e o l y s i s ( G o ld b e rg and Ram
w e ll,
1975).
Niswender
,al. (1976) n o ted t h a t d e c l i n i n g blood flow
t o t h e CL c o n t a i n i n g o v a r y o r t h e CL i t s e l f
a r e among t h e f i r s t
r e s p o n s e s d u r i n g n a t u r a l l u t e o l y s i s o r a f t e r e x o g e n o u s PGF2a (a s
r e v ie w e d , by I n s k e e p and M urdoch,
1980).
T h ese r e v i e w e r s
c ite d
o p p o s itio n t o d e crea se d blood flow as th e mechanism o f l u t e o l y s i s i n
which t o t a l p re v e n tio n o f blood flow t o th e CL f o r 45 m in u te s did n o t
cause CL r e g r e s s io n .
p ro b a b ly
I t has been concluded t h a t reduced blood flow i s
a " c o n s e q u e n c e *1 r a t h e r
(Inskeep and Murdoch,
M cC lellan sfc. a l .
th a n
th e
"cause"
of
lu te o ly sis
1980).
(1977) r e p o r te d in c r e a s e d ly so so m a l a c t i v i t y i n
18
re g e ssin g lu te a l c e lls .
T h is d i d n o t o c c u r u n t i l a f t e r t h e i n i t i a l
d e c lin e in p ro g e stero n e s y n th e s is .
I t may be h y p o t h e s i z e d t h a t
lysosom es a r e f u n c tio n a l in m o rp h o lo g ic a l l u t e o l y s i s but a re n o t
in v o lv e d i n i n i t i a t i n g f u n q t i o n a l l u t e o l y s i s i n d i c a t e d by d e c l i n i n g ,
plasm a p ro g e s te ro n e c o n c e n tr a tio n s .
Types o f l u t e o l v t i c a g e n ts .
P rec o c io u s l u t e o l y s i s i n th e bovine
c a n be i n d u c e d w i t h e x o g e n o u s o x y t o c i n (A rm s tr o n g and H a n s e l, I 959;
H a n s e l and W agner,
1960; G i n t h e r _§£. a l . t 1967) when a d m i n i s t e r e d
betw een days 3 and 7 o f th e c y c le .
Hansel £& &L. (1959) r e p o r te d a 7 -
day i n t e r v a l i n s u b s e q u e n t o n s e t o f e s t r u s i n h e i f e r s r e c e i v i n g
o x y to c in d u rin g th e f i r s t seven days o f t h e i r c y c le .
F e r t i l i t y to
t h i s e s t r u s was c o m p a r a b le t o u n t r e a t e d c o n t r o l s b u t low a n im a l
numbers n egated s i g n i f i c a n c e .
E stro g e n s
have
been r e p o r te d
to
in d u c e
a d m in is te r e d to c y c lin g h e i f e r s (W iltbank s i a l , ,
a l.f
1964) o r
cows
(R ahlm ann and Cupps,
lu te o ly s is
1961; K altenbach s i
1962) d u r i n g
F e r t i l i t y a t th e su b seq u en t e s t r u s i s low (W iltbank
Brunner
si
S i.
si S i . ,
th e
d ie stru s.
1961).
(1969) s tu d ie d th e l u t e o l y t i c e f f e c t s o f o x y to cin
and e s t r o g e n by u t i l i z i n g h y s t e r e c t o m i z e d h e i f e r s .
th a t
w hen
lu te o ly tic
m echanism
of
th e se
They c o n c lu d e d
two compounds i n v o l v e d
s t i m u l a t i o n o f normal u t e r i n e m ediated l u t e o l y s i s , which was review ed
i n an e a r l i e r s e c tio n .
19
With th e d is c o v e ry o f th e l u t e o l y t i c e f f e c t s o f PGF2 a , a t t e n t i o n
has been tu rn e d tow ard th e use o f t h i s compound to sy n ch ro n ize bovine
fe m a le s f o r a r t i f i c i a l in s e m in a tio n .
A s t a b l e trom etham ine s a l t of
PGF2 a (THAM) has been developed and i s now m arketed a s L u taly se® (The
U pjohn Company).
A ls o , p o t e n t PGF2a a n a l o g u e s ( I C I - 7 9 9 3 9 and I C I -
80996, I m p e r ia l Chemical I n d u s t r i e s ) have been s y n th e s iz e d and shown
t o be e f f e c t i v e l u t e o l y t i c a g e n t s i n c a t t l e ( T e r v i t s i , sJL.$ 1973;
C ooper,
1974; D obson s i . S i . » 1 9 75).
c lo p ro ste n o l)
is
m a r k e te d i n
E stru m a te ®
(IC I-8 0 9 9 6 ,
t h e U n ite d Kingdom b u t i s
not y et
approved f o r u se i n th e U nited S ta te s .
E x ten siv e r e s e a r c h has been c a r r i e d o u t i n th e p a s t te n y e a r s t o
d e v e l o p e f f e c t i v e and e f f i c i e n t t r e a t m e n t s y s t e m s f o r . PGF201. E a r l y
r e s e a r c h d e term in e d t h a t PGF2a was e f f e c t i v e only on c a t t l e t h a t a r e
i n d i e s t r u s o f t h e i r c y c l e (d a y s 5 t o 16).
60% o f a randomly c y c lin g herd.
T h is i n c l u d e s o n ly a b o u t
To be t o t a l l y a c c e p ta b le , system s o f
tr e a tm e n t were n e c e s sa ry t o accommodate a n im a ls between days I to 4
and 17 t o 21 o f t h e c y c l e .
S m all doses o f PGF2a (0.5-6.0 g) a d m in is te r e d i n t r a u t e r i n e l y (IU)
w e re f i r s t s t u d i e d a s a m ethod o f t r e a t m e n t ( L i e h r e t a l . . 1972;
Rowson s i a i . ,
1972; H a fs s i a l ..
1974).
The h a z a r d o f i n d u c i n g
u t e r i n e i n f e c t i o n s w ith t h i s method o f tr e a tm e n t has prompted the use
o f o th e r r o u t e s o f a d m i n i s t r a t i o n (Seg u in, 1980).
su b cu tan eo u s (SC) and
in tr a v e n o u s
(IV)
In tr a m u s c u la r (IM),
in je c tio n s
of
25 t o 3Q mg
20
PGFga
o r 0.5 mg c l o p r o s t e n o l a r e e f f e c t i v e i n in d u c in g l u t e o l y s i s i n
c a t t l e ( L a u d e r d a l e , 1972; C o o p er, 197^; H a fs jgjLSl., 1974; S t e l l f l u g
e t a l . f 1975;
L a u d e r d a l e sJl a l . ,
1977).
S in c e t h e IM m ethod i s
p r o b a b l y t h e m p st c o n v e n i e n t i t h a s b e e n a c c e p t e d a s t h e r o u t e o f
a d m i n i s t r a t i o n f o r p ro d u c e rs t o use.
M ethods o f a d m i n i s t r a t i o n .
S in c e PGFg01 i s o n l y e f f e c t i v e on
c a t t l e t h a t a r e i n t h e d i e s t r u s , L a u d e r d a l e jg±.
(1974) p ro p o s e d
u s in g r e c t a l p a l p a t i o n o f th e o v a r ie s t o d e te rm in e r e p r o d u c tiv e s t a t u s
and t r e a t i n g o n ly t h o s e i n d i v i d u a l s d i a g n o s e d t o h a v e a c t i v e CL’s.
Cows n o t t r e a t e d i n i t i a l l y a r e e i t h e r p a l p a t e d one week l a t e r and
t r e a t e d a c c o r d in g ly or sim p ly i n j e c t e d w ith o u t p a lp a t io n .
A 30 mg
PGFga -THAM ( t r o m e t h a m i n e ) d o s e was a d m i n i s t e r e d e i t h e r IM o r SC t o
t r e a t e d cow s.
One g ro u p o f t r e a t e d cows was i n s e m i n a t e d 12 h o u r s
a f t e r d e te c te d e s t r u s f o r a 7-day p e rio d w h ile a n o th e r was in s e m in a te d
a t 72 and 96 h o u r s p o s t - t r e a t m e n t w i t h o u t r e g a r d t o e s t r u s .
The
u n t r e a t e d c o n t r o l s w ere in s e m in a te d 12 h ours a f t e r e s t r u s d u rin g an 18
t o 25 day p e r i o d . F e r t i l i t y was b a s e d on number o f a n i m a l s e i t h e r
r e s p o n d i n g t o PGFga o r o b s e r v e d i n e s t r u s .
The r e s u l t s showed no
d i f f e r e n c e (P>.05) i n f e r t i l i t y among t r e a t e d and u n tr e a te d cows.
Another method t o d e te rm in e s u s c e p t i b l e c a n d id a te s f o r PGFga i s
h e a t d e t e c t i o n p r i o r t o t r e a t m e n t and i n j e c t i n g o n ly t h o s e a n i m a l s
which a r e 5 t o 16 days p o s t e s t r u s (Tervi t e t al.« 1973; M acm illan e t
I
21
&!.,
1980).
E ffe c tiv e
s y n c h ro n iz a tio n
of
e stru s
w as r e p o r t e d
f o ll o w i n g t h i s method.
Both o f th e s e sy stem s a r e e f f e c t i v e re d u c in g w astag e o f drug on
a n im a ls t h a t a r e n o t i n th e p ro p e r s ta g e
to resp o n d .
B u t,
th e
p r a c t i c a l i t y o f a p p ly in g th e s e methods t o range c a t t l e s i t u a t i o n s i s
q u e s tio n a b le .
A more a t t r a c t i v e system to b e e f c a t t l e p ro d u c e rs would
in c o r p o r a t e a s i n g l e p re d e te rm in e d tim ed in s e m in a tio n w ith o u t th e need
to d e t e c t e s t r u s (appointm ent breed).
Lambert
a l . f (1975) f i r s t proposed a system whereby a group o f
b e e f cows and h e i f e r s were d e te c te d f o r e s t r u s and in s e m in a te d about
12 h r a f te r w a r d f o r a 5-day p e rio d .
A ll a n im a ls n o t d e te c te d by t h i s
tim e w ere i n j e c t e d (IM) w ith 33*5 mg PGF2a - THAM and in s e m in a te d a t 12
h r a f t e r e s t r u s u n t i l 72 hr p o s t - t r e a t m e n t .
At t h i s tim e a l l unbred
cows w e re i n s e m i n a t e d w i t h o u t r e g a r d t o e s t r u s ( a p p o i n t m e n t b r e d ) .
The r e s u l t s o f t h i s t r i a l i n d i c a t e d a s h ig h f i r s t s e r v i c e co n cep tio n
ra te
in
th e
tre a te d
g ro u p
(53$)
as
in
th e
u n tre a te d
c o n tro ls
i n s e m i n a t e d f o r a 22 t o 30 day p e r i o d (5 7 $ ), b u t , f e r t i l i t y a t t h e 72
hr
a p p o in tm en t
b re e d in g
was
a l s o r e p o r t e d low f e r t i l i t y
low
(17$).
D aily
si.
jlL,,
(1980)
i n t h e a p p o i n t m e n t b r e d cow s i n t h i s
system .
A ttem pts t o improve f e r t i l i t y
i n t h i s system by sch e d u lin g th e
a p p o i n t m e n t b r e e d i n g a t 80 h r i n s t e a d
o f 72 h r P o s t-P G F 2a w e re
r e p o r t e d (Lambert s i . 3h>t 1976; Donaldson,
1977, Han and Moody, 1979;
22
Hanks e t a l . f 1980).
C o n c e p tio n r a t e s i n t r e a t e d c a t t l e b r e d t o an
ob serv ed e s t r u s was a t l e a s t as high a s th o se i n u n tr e a te d c o n t r o l s i n
a l l stu d ie s.
Each o f t h e s e r e p o r t s show ed a low c o n c e p t i o n r a t e i n
th o s e a n im a ls a p p o in tm e n t bred w ith o u t re g a rd to e s t r u s .
r e p o r t s i n d i c a t e low f e r t i l i t y
b re e d in g i n t h i s system .
These
i n a n i m a l s b re d a t an a p p o i n t m e n t
I t may be concluded both th e 72 h r and 80 h r
a p p o in tm e n t b re e d in g a r e n o t e f f e c t i v e p ro c e d u re s to use a f t e r a
s i n g l e PGF2 a i n j e c t i o n b e c a u s e e x t e n s i v e w a s t a g e o f sem en r e s u l t s
(D o n a ld s o n , 1980).
A n o th e r s y s te m u t i l i z i n g a s i n g l e i n j e c t i o n o f PGF2q t h a t h a s
been proposed and in v o lv e s i n j e c t i n g a l l cows a t th e b e g in n in g o f th e
b re e d in g sea so n and in s e m in a tin g by e s t r u s f o r 9 o r 10 days (Doornbps
and A n d e rso n ,
1979; Han and Moody, 1979).
B o th o f t h e s e s t u d i e s
r e p o r t e d h i g h e r Al p re g n a n c y r a t e s o f t r e a t e d cow s t h a n u n t r e a t e d
c o n t r o l s in s e m in a te d f o r th e same p e r i o d .
T h is i n d i c a t e d e f f e c t i v e
s y n c h r o n iz a tio n bu t n o t a l l t r e a t e d a n im a ls would respond i f th e r e i s
random d i s t r i b u t i o n o f c y c lin g .
T h e re fo re w astage o f drug o c cu rred i n
th e s e an im a ls.
E s tro u s c o n t r o l sy ste m s i n c a t t l e in v o lv in g s i n g l e i n j e c t i o n s o f
PGF2a o r i t s a n a l o g u e s a r e p r o m i s i n g m e th o d s f o r s h o r t e n i n g an Al
season.
D e te c tio n of e s tr u s
c a n n o t be. f e a s i b l y
e lim in a te d
and
i n s e m i n a t i o n s h o u l d be a d m i n i s t e r e d o n ly i n r e f e r e n c e t o e s t r u s .
A ttem pts t o ap p o in tm e n t breed i n th e s e sy stem s have f a i l e d ,
probably
23
due t o v a r i a t i o n among i n d i v i d u a l s i n th e i n t e r v a l from tr e a tm e n t to
o n s e t o f e s t r u s and o v u l a t i o n ( J o h n s o n ,
1978; R e f s a l and S e g u in ,
1980 ).
A p r a c t i c a l system u s in g two i n j e c t i o n s o f PGFga 10 days a p a r t to
sy n ch ro n ize e s t r u s i n a group o f randomly c y c lin g bovine fe m a le s was
proposed by Inskeep (1973) and King and R obertson (1974).
This system
i s based on th e th e o ry t h a t th e i n i t i a l i n j e c t i o n would r e g r e s s th e CL
i n a l l i n d i v i d u a l s t h a t % ere b e tw e e n d a y s 5 and 16 o f t h e i r c y c l e .
T h e se i n d i v i d u a l s w o u ld r e t u r n t o e s t r u s 2 t o 4 d a y s l a t e r .
would be betw een days 6 and 8 a t th e second i n j e c t i o n .
They
Those a n im a ls
i n d a y s 17 t o 21 a t t h e i n i t i a l i n j e c t i o n w o u ld go t h r o u g h a n o rm a l
e s t r u s and be b e tw e e n d a y s 5 and 9 a t t h e se c o n d i n j e c t i o n .
Those
a n im a ls betw een days 0 and 5 a t th e f i r s t i n j e c t i o n would be a t day 10
th rough 15
a t th e second i n j e c t i o n .
T h e o r e t i c a l l y , t h i s w o u ld .p la c e
a l l a n im a ls i n d i e s t r u s to be re s p o n s iv e to th e l a s t PGFga i n j e c t i o n .
E i g h ty - th r e e p e r c e n t o f 30 c y c li n g H o ls te in h e i f e r s showed g s t r u s
2 t o 4 d a y s f o l l o w i n g t r e a t m e n t i n t h e s t u d y by K ing and R o b e r ts o n
(1 9 7 4 ).
T hese r e s u l t s w e re e n l i g h t e n i n g ,
d i a g n o s i s was n e c e s s a r y .
s i n c e no p r e t r e a t m e n t
A lth o u g h o n l y 40$ o f t h e s e i n d i v i d u a l s
c o n c e i v e d t o i n s e m i n a t i o n s a t o b s e r v e d e s t r u s and 12 h r l a t e r , t h i s
w as n o t d i f f e r e n t fr o m 54$ o f c o n t r o l h e i f e r s t h a t c o n c e iv e d t o
s i m i l a r in s e m in a tio n s .
P r e l i m i n a r y r e s u l t s r e p o r t e d by Cooper (1974) show ed s i m i l a r
24
success
in
130 d a i r y
h e ife rs re c e iv in g
i n j e c t i o n s 10 t o 12 d a y s a p a r t .
tw o 0.5 mg c l o p r o s t e n o l
E i g h t y - n i n e o f t h e s e a n i m a l s w e re
in s e m in a te d 12 h r a f t e r d e te c te d e s t r u s f o llo w in g t r e a tm e n t.
Another
30 t r e a t e d h i e f e r s w e re i n s e m i n a t e d t w i c e a t 72 and 96 h r . a f t e r t h e
second i n j e c t i o n w ith o u t re g a rd f o r e s t r u s .
Conception r a t e s based on
r e c t a l p a l p a t i o n e i g h t w eek s a f t e r b r e e d i n g w e re i d e n t i c a l i n b o th
t r e a t e d and u n t r e a t e d g r o u p s .
In a d d itio n t h i s a u th o r re p o rte d a
d e t a i l e d stu d y on a n o th e r 45 h e i f e r s r e c e i v i n g two i n j e c t i o n s o f 0.5
mg c l o p r o s t e n o l 11 d a y s a p a r t .
Of 43 h e i f e r s sh o w in g e s t r u s a f t e r
t r e a t m e n t , 39 w e re d e t e c t e d b e tw e e n 48 and 72 h r a f t e r t h e s e c o n d
i n j e c t i o n ; th e o t h e r fo u r were observed i n e s t r u s betw een 72 and 96 hr
p o st-tre a tm e n t.
O v u latio n o c cu rred i n 4 h e i f e r s between 48 and 72 hr,
34 h e i f e r s b e tw e e n 72 and 96 h r and 5 h e i f e r s b e tw e e n 96 and 120 h r
p o st-tre a tm e n t.
Due t o t h e s h o r t e r i n t e r v a l o f e s t r u s f o l l o w i n g t h i s t r e a t m e n t
th e p o s s i b i l i t y o f u s in g an app o in tm en t b re e d in g seemed more prom ising.
H a fssJL sJL * (1 9 7 5 a ) u s e d tw o IM i n j e c t i o n s o f PGFg^ 12 d a y s a p a r t on
d a ir y h e i f e r s and s u ck le d b e ef cows to sy n ch ro n ize e s t r u s .
T re a te d -
h e i f e r s w ere in s e m in a te d tw ic e a t 70 h r and 88 h r p o s t tr e a tm e n t w ith
sem en fro m t h e same b u l l .
T r e a t e d cows w e re i n s e m i n a t e d o n ce w i t h
semen from one breed o f b u l l a t 70 h r p o s t - t r e a t m e n t and a g a in a t 88
h r p o s t - t r e a t m e n t w i t h sem en fro m a n o t h e r b r e e d o f b u l l .
U sin g
c a l v i n g d a t a t o d e t e r m i n e r e s u l t s , th e y r e p o r t e d 54% c o n c e p t i o n i n
25
h e i f e r s bred a t 70 and 88 h r Post-PGF2a compared to 55% co n ce p tio n i n
u n tr e a te d h e i f e r s ;
th e s e w ere in s e m in a te d a f t e r d e te c te d e s t r u s f o r a
th re e -w e e k p e rio d .
F o rty -o n e p e rc e n t o f th e tr e a te d cows conceived to
th e
tim e d i n s e m i n a t i o n s
com pared t o
44% o f th e
u n tre a te d
cows
c o n c e iv in g t o i n s e m i n a t i o n a f t e r , ah o b s e r v e d e s t r u s f o r a 2 5 -d a y
p e rio d .
H ig h e s t f e r t i l i t y
in
th e
tre a te d
a n im a ls
w as am ong
i n d i v i d u a l s d e t e c t e d i n e s t r u s 3 to 5 d a y s a f t e r t r e a t m e n t .
S ix ty -
e i g h t p e r c e n t o f tihe t r e a t e d h e i f e r s an d 62% o f th e t r e a t e d cows
showed e s t r u s d u rin g t h i s p e rio d .
More tr e a t e d cows conceived to th e
7 0 -h r in s e m in a tio n
8 8 -h r in s e m in a tio n
th a n to
th e
d i f f e r e n c e w as n o t s u b s t a n t i a t e d .
a lth o u g h
th e
The a u t h o r s c o n j e c t u r e d t h a t a
s in g le in s e m in a tio n a t 80- h r p o s t- tr e a tm e n t could produce s a t i s f a c t o r y
re s u lts .
A l a r g e f i e l d t r i a l was c o n d u c te d on 960 h e i f e r s and 392 b e e f
cows to t e s t th e f e a s i b i l i t y o f an 80 h r app o in tm en t b re e d in g (Hafs e t
a l . f 1975b).
T re a te d a n im a ls re c e iv e d two in j e c t i o n s o f e i t h e r 0.5 mg
c l o p r o s t e n o l o r 30 mg PGF2a-THAM 10 t o 12 d a y s a p a r t .
One g ro u p o f
t r e a t e d a n im a ls was in s e m in a te d tw ic e a t 70 and 88 h r a f t e r tre a tm e n t.
The o t h e r t r e a t e d g ro u p w as in s e m in a te d once a t 80. h r p o s t - PGF2a.
U n tr e a te d c o n t r o l s w e re i n s e m in a te d fo llo w in g o b serv ed e s tr u s .
In
th e c o n tr o ls bred a f t e r d e te c te d e s t r u s , 51% o f th e h e i f e r s and 59% o f
th e cows w ere diagnosed p re g n a n t based on e i t h e r r e c t a l . p a lp a tio n or
n o n re tu rn r a t e .
Among tr e a te d a n im a ls 63% o f th e h e i f e r s and 58% o f
26
th e cows in s e m in a te d tw ic e w ere diag n o sed p reg n an t w h ile 62% o f th e
h e i f e r s and 57% o f th e cow s in s e m i n a t e d on ce w ere p r e g n a n t.
a u th o rs
r e p o r te d
no
d if f e r e n c e
c lo p ro s te n o l tre a tm e n t.
tre a tm e n t
in
fe rtility
T hey c o n c l u d e d
w as e q u i v a l e n t
to
c o n tro ls
The
a f t e r PGFg^-THAM o r
fe rtility
a fte r
and f e r t i l i t y
PGFg31
from one
in s e m in a tio n (80 h r) was eq u al to t h a t from two in s e m in a tio n s (70 and
88 h r) a f t e r p ro s ta g la n d in .
Hafs s i . s i , ,
(1978) r e p o rte d s i m i l a r f e r t i l i t y r e s u l t s i n h e i f e r s
and b e e f cows r e c e iv in g two PGFg^ i n j e c t i o n s 11 days a p a r t and e i t h e r
in s e m in a te d tw ic e a t 70 and 88 h r p o s t- tr e a tm e n t o r once a t 80 h r p o st
tr e a tm e n t.
th e t r e a t e d
A lso,
they re p o rte d t h a t o n ly 15% more semen was used on
cow s in s e m in a te d o n ce (80 h r ) th a n t h a t u se d on th e
u n tre a te d c o n tr o ls .
The two in s e m in a tio n system r e q u ire d
107% more
semen th a n th e u n tre a te d c o n tro ls .
A nother p re d e te rm in e d (app o in tm en t) b re e d in g tim e o f 72 h r p o s tPGFga was s tu d ie d .
Cooper s i a l . (1976) re p o rte d lo w er c o n ce p tio n i n
cow s and h e i f e r s in s e m in a te d o n c e a t 72 h r a f t e r tw o i n j e c t i o n s o f
c lo p r o s te n o l 11 days a p a r t th a n t h a t i n tr e a te d a n im a ls in se m in a te d
tw ic e a t 72 and 96 h r Post-PGFga o r c o n tr o ls bred by n a tu r a l s e r v ic e
f o r 21 d a y s .
O ver 3 ,0 0 0 a n im a ls w e re u s e d i n t h i s s tu d y .
S im ila r
r e s u l t s fo llo w in g t h i s system w ere r e p o r te d by S c h u ltz .e t a l . f (1977).
Moody and
L au d erd ale
(1977)
compared
in s e m in a tio n
a fte r
two
PGFga i n j e c t i o n s i n b e e f cows e i t h e r a t 80 h r p o s t- tr e a tm d n t o r a f t e r
27
d e te c te d
e s tru s
fro m
day 2 to
s i g n i f i c a n t l y lo w e r f i r s t
5 p o s t tre a tm e n t.
s e rv ic e
They r e p o r t e d
c o n c e p tio n r a t e s i n
th e 8 0 -h r
a p p o in tm en t bred group th a n i n th e t r e a t e d cows o r u n tr e a te d c o n tro ls
in s e m in a te d a f t e r d e te c te d e s tr u s .
The t o t a l pregnancy r a t e
(number
p r e g n a n t f t o t a l i n g ro u p ) f o r th e a p p o in tm e n t b re d g ro u p was h o t
d i f f e r e n t fro m t h p t i n th e t r e a t e d
d e te c te d e s tr u s .
g ro u p in s e m in a te d o n ly a f t e r
Both tr e a t e d groups had a s i g n i f i c a n t l y h ig h e r t o t a l
p re g n a n c y r a t e by day 5 o f th e b r e e d in g s e a s o n th a n th e u n t r e a t e d
c o n tr o ls .
R e s u l t s o f t h e s e t r i a l s u s in g tw o i n j e c t i o n s o f PGF2a 10 to 12
days a p a r t to sy n c h ro n iz e e s t r u s i n c a t t l e in d ic a te t h a t t h i s may be a
f e a s i b l e s y s te m
to u t i l i z e Al w ith o u t h e a t d e t e c t i o n .
The 80 h r
a p p o in tm en t b re e d in g i s probably th e b e t t e r tim ed in s e m in a tio n .
Many
f a c t o r s h a v e b e e n p o in te d o u t i n t h e l i t e r a t u r e t h a t may h e lp to
c o n tr ib u te to th e s u c c e ss o f t h i s b re e d in g system .
The v a r i a b i l i t y in
t h e o n s e t o f e s t r u s and o v u l a t i o n f o l l o w i n g t h i s t r e a t m e n t may be a
p ro b le m i n l a c t a t i n g
d a iry
co w s
(M a c m illa n ,
1978;
R o ch e a n d
P r e n d i v i l l e , 1979)? f o r h e i f e r s t h i s d o e s n o t a p p e a r to be a p ro b le m
(Johnson, 1978; R e fsa l and Sequin, 1980) bu t i s m a rg in a l i n b e ef cows
(H a f s &£. a I . f
19 7 5 a ).
B u t,
it
has
been r e p o rte d
th a t
th is
s y n c h ro n iz a tio n system i s n o t s u c c e s s f u l i n Brahman c a t t l e (H ardin e t
a l . f 1980).
S easonal v a r i a t i o n s o f o n s e t o f e s tr u s fo llo w in g PGF2a in
h e i f e r s w e re r e p o r t e d by B r i t t
a l . ( 1978).
One m a jo r b e n e f i t o f
28
t h i s system was re p o rte d by E sselm ont sJL jal.
e v a l u a t e d th e r e p r o d u c t i v e e f f i c i e n c y
(1977).
These a u th o rs
o f a n im a ls r e c e i v i n g
th is
t r e a t m e n t and fo u n d t h a t th e i n t e r v a l s fro m th e b e g in n in g o f th e
b r e e d in g s e a s o n t o f i r s t s e r v i c e and c o n c e p tio n w e re s i g n i f i c a n t l y
r e d u c e d by 13.6 and 12.5 d a y s , r e s p e c t i v e l y , co m p ared t o u n t r e a t e d
c o n tr o ls .
Due
to
th e
v a ria tio n
tre a tm e n t in c a t t l e ,
s tu d ie s
in
onset
w e re
of .e s tru s
c o n d u c te d
p r e c is io n
of
re g im e n .
I t i s h y p o th e s i z e d t h a t t h i s
to
a fte r
PGF2 a
in c re a s e
th e
synchrony by in c o rp o ra tin g e s tro g e n i n t o th e tre a tm e n t
w o u ld
in d u c e
a
m ore
s y n c h r o n iz e d e s t r u s
and o v u l a t i o n . I n j e c t i o n s o f E2 48 h r a f t e r
e i t h e r a double PGF2a
i n j e c t i o n system o r i n t r a - u t e r i ne in f u s io n s o f
PGF2a i n b e e f f e m a le s w e re e f f e c t i v e i n i n c r e a s i n g t h e p r e c i s i o n o f
s y n c h ro n y .
F e rtility
a f t e r t r e a t m e n t was c o m p a ra b le t o t h a t i n
u n t r e a t e d c o n t r o l s and P G F ^ -a lo n e t r e a t e d f e m a le s ( I n s k e e o e t a l „ T
1975; Welch s t Si f t
1975; P e te rs s i flln, 1977).
P r a c tic a l a p p lic a tio n
o f t h i s s y s te m may n o t be a c c e p t a b l e to b e e f p r o d u c e r s due to th e
added c o s t o f tre a tm e n t and th e e x tr a h a n d lin g o f a n im a ls.
The
use
of
GnRH i n j e c t i o n s
a fte r
PGF2 a t r e a t m e n t
to
m ore
p r e c i s e l y s y n c h r o n iz e th e LH p eak and s u b s e q u e n t o v u l a t i o n h a s b een
s tu d ie d .
I t w as h y p o th e s i z e d t h a t t h i s may im p ro v e f e r t i l i t y i n a
group o f cows bred a t an ap p o in tm en t b re e d in g .
th is
w as r e p o r t e d
F a ilu r e to acco m p lish
by Tobey and H a n se l ( 19 7 5 ),
K in k ie (1976) and
29
B u r f e n in g .sJi. s !.. (1978)
when
100
UgGnRH
was
a f t e r PGFg^ and in s e m in a tio n a t 72 h r Post-PGFga.
s u p p re ss b e h a v io ra l e s tr u s i n
c a ttle
when
in je c te d
60
hr
GnRH i s re p o rte d to
a d m in is te re d a f t e r PGFga
( T h a tc h e r and C h e n a u lt, 1976; R o d riq u e z
, I 9 75), a lth o u g h t h i s
w as n o t e v i d e n t i n a s tu d y by B r i t t sJi. jaJL. (1975)
when GnRH was
a d m in is te re d 11 days p r i o r to th e f i r s t PGFga i n j e c tio n .
Use o f P ro g esta g en and L u te o lv tic Agent C om binations.
M echanism o f C o n t r o l .
p ro g e s ta g e n s
( i.e .,
16
L ong te r m
to
21
use
d ay s)
o f p ro g e s te ro n e
re s u lts
in
or
a c c e p ta b le
s y n c h r o n i z a t i o n o f e s t r u s i n b o v in e f e m a le s b u t f e r t i l i t y i s lo w e r
t h a n n o rm a l a t t h e e s t r u s a f t e r t r e a t m e n t .
H ow ever,
a c c e p ta b le
f e r t i l i t y i n bovine fe m a le s i s acco m p lish ed when p ro g e sta g e n tre a tm e n t
i s s h o rte n e d to 9 to 12 days, b u t e f f e c t i v e s y n c h ro n iz a tio n i s low ered
due to f a i l u r e o f l u t e o l y s i s to o ccu r in some tr e a te d a n im a ls.
b e e n h y p o th e s i z e d
th a t
a lu te o ly tic
agent
in c o rp o ra te d
I t has
at
th e
i n i t i a t i o n o f a 9-day p ro g e sta g e n t r e a t m e n t w o u ld i n s u r e l u t e o l y s i s
and w o u ld r e s u l t i n a m ore a c c e p t a b l e e s t r o u s s y n c h r o n i z a t i o n and
f e r t i l i t y , r a t e (Lamming s£. s i ,
1979).
M ethods o f a d m i n i s t r a t i o n .
and a c c e p ta b le f e r t i l i t y
S u c c e s s fu l e s tr o u s s y n c h ro n iz a tio n
fo llo w in g 9 to 12 day p ro g e sta g e n tre a tm e n t
w i t h i n j e c t i o n s o f Eg a d m i n i s t e r e d w hen t r e a t m e n t i s i n i t i a t e d i n
bovine fe m a le s w ere re p o rte d u s in g sp o n g e p e s s a r i e s (S re e n a n , 1975;
30
S re e n a n and M u l v e h i l l , 1975) and PRID (R oche .§£ sJL., 1976; Drew
a l . f 1978).
V a r ia b le s u c c e s s w as r e p o r t e d when E2 i n j e c t i o n s w e re
a d m in is te re d a t i n i t i a t i o n o f a 9-day su b c u ta n e o u s-im p la n t tre a tm e n t
reg im en (Anderson s i A l.,
1969; W iltbank s£. a i , ,
I 972; W hitm an s i A l., I 97 2 ).
1971; B u r r e ll s i aJU,
O th e r r e s e a r c h i n t h i s m eth o d show ed
th a t by in c r e a s in g th e le v e l o f p ro g e sta g e n i n th e im p la n t (Woody and
A benes, 1 9 7 5 ), p l a c i n g t h e p r o g e s ta g e n i n t h e w a l l and t h e lu m en o f
th e im p la n t (Wideman s i A l,,
1969) and (o r) a d m in is te r in g an i n j e c t i o n
o f p r o g e s ta g e n , a lo n g w ith th e e s t r o g e n a t th e tim e t h e i m p la n t w as
i n s e r t e d ( W is h a r t and Young, 1974; W i s h a r t s i a i . , 1977) r e s u l t e d i n
more a c c e p ta b le synchrony and f e r t i l i t y ;
I t i s h y p o th e siz e d t h a t t h i s
w as due t o an a n t i l u t e o t r o p i c e f f e c t p ro d u c e d by th e h i g h e r i n i t i a l
le v e l o f p ro g e sta g e n on CL t h a t w ere j u s t d ev elo p in g a t th e i n i t i a t i o n
o f tr e a tm e n t (Lamming s t a l? , 1979).
T h is le d to th e developm ent o f a
s y n c h r o n i z a t i o n s y s te m know n a s S y n c h r o - M a t e - E ^ (SMB, G.D. S e a r l e
C o.).
T h is s y s te m c o n s i s t s o f a s i l a s t i c im p la n t c o n t a i n i n g 6 mg
n o rg e sto m et (SC-21009) p la c e d su b cu ta n e o u sly in th e e a r f o r 9 days, and
a s i n g l e i n j e c t i o n o f 6 mg E2 and 3 mg n o r g e s to m e t a d m i n i s t e r e d a t
tim e o f im p la n t in s e r t i o n .
S u c c e ssfu l s y n c h ro n iz a tio n o f e s tr u s and
f e r t i l i t y a t a tim ed in s e m in a tio n 48 to 54 h r a f t e r im p la n t rem oval i n
h e i f e r s r e c e i v i n g t h i s s y s te m w as r e p o r t e d by W iltb a n k and S p i t z e r
(1978).
(G oodell
The SMB tr e a tm e n t was n o t as s u c c e s s fu l i n su c k le d b e e f cows
s t.
a l.,
1976),
but
some
im provem ent
was
n o ted
a fte r
31
i n c o r p o r a t i n g GnRH i n j e c t i o n s p r i o r t o i n s e m i n a t i o n (Z a le d e t a lo ,
1976) o r
c a lf
re m o v a l f o r
24
to
48 h r
1
■
in s e m in a tio n s
(48 to
(S hang)
p rio r
to
tim e d
■
.
54 h r p o s t - t r e a t m e n t ) (M ares s i .
1977;.
K altenbach and Dunn, 197.9; K ise r s i a l . . 1979; P e te rs o n s i s L ,
1979).
One b e n e f it o f p r o g e s ta g e n - lu te o ly s in c o m b in atio n sy stem s i s t h a t they
may in d u c e c y c l i n g a c t i v i t y i n a n e s t r o u s cows (Drew s i SJL.» 1978;
Mares s i Sl.»
1979) and p re p u b e rta l h e i f e r s (G o n z a le z -P a d illa e t al„,
1975).
C om binations o f p ro g e sta g e n s and PGF2ot have been s tu d ie d i n which
PGF2ot was a d m in is te re d a t o r n e ar th e end o f a 5 to 8 day p ro g estag en
tre a tm e n t.
F e rtility
o f b e e f and d a i r y
f e m a le s r e c e i v i n g
th is
t r e a t m e n t w as r e p o r t e d to be s a t i s f a c t o r y ( W is h a r t,
1974; R oche,
1976b; S t a u f f e r s i A l . » 1976; C h u p in s i A l.,
Moody a t a I .
1977).
( 1980) w ere un ab le to show eviden ce t h a t i n j e c t i o n s o f Py e i t h e r 24 o r
5 days p rio r
to
a s in g le
PGF2ot i n j e c t i o n
r e p r o d u c tiv e . perfo rm an ce i n b e e f h e i f e r s .
c y c lin g r a t e (60%) i n th e s e a n im a ls.
e ffe c tiv e ly
im p ro v ed
The m ajor problem was a low
T h is was d eterm in ed by th e r a t e
o f d e t e c t i o n o f e s t r u s i n u n t r e a t e d c o n t r o l s f o r a 1 0 -d ay p e r io d .
These r e s u l t s f u r t h e r su g g e st t h a t t h i s sy stem , l i k e a l l o th e r system s
o f s y n c h r o n i z a t i o n d is c u s s e d i n t h i s r e v ie w , i s m o st a c c e p t a b l e to
p ro d u c e rs when i t i s used on a c ti v e ly c y c lin g bovine fe m a le s.
STATEMENT OF PROBLEM
P ro s ta g la n d in Fga i s
th e o n ly s y n c h r o n i z a t i o n a g e n t t h a t i s
approved by th e Food Drug A d m in is tra tio n f o r use by U nited S ta te s b e ef
and d a iry p ro d u c e rs.
b r e e d in g ) a f t e r
A r t i f i c i a l i n s e m i n a t i o n a t 80 h r ( a p p o in tm e n t
tw o i n j e c t i o n s
o f PGF20t 10 t o
12 d a y s a p a r t i s
p ro b ab ly th e m ost i n v i t i n g b re e d in g system because i t n e g a te s th e need
fo r d e te c tin g e s tr u s .
The e f f i c i e n c y o f t h i s s y s te m h a s n o t b een
s a t i s f a c t o r y to p ro d u c e rs because o f lo w er th a n ex p ected p ro d u c tio n o f
Al c a l v e s , e s p e c i a l l y i n ra n g e b e e f o p e r a t i o n s .
th e s e s tu d ie s w ere:
The o b j e c t i v e s o f
I) to d e te rm in e i f e s tr u s can be sy n ch ro n ized i n
su c k le d b e e f cows ( a t l e a s t 50 days p o st-p a rtu rn ) w ith two in j e c t i o n s
o f PGF2a 11 d a y s a p a r t ;
2) to d e te r m in e i f
p re g n a n c y r a t e
fro m
a r t i f i c i a l i n s e m i n a t i o n a t 12 h r a f t e r d e t e c t e d e s t r u s up t o 80 h r
a f t e r t r e a t m e n t th e n th e r e s i d u a l ( i . e . , n o t d e t e c t e d by 80 h r p o s t ­
t r e a t m e n t ) b re d a t 80 h r i s d i f f e r e n t fro m t h a t w hen a r t i f i c i a l
in s e m in a tio n o c c u rs only a t 80 h r a f t e r t h i s double i n j e c t i o n system ;
3) t o d e te r m in e i f p re g n a n c y r a t e fro m a r t i f i c i a l i n s e m i n a t i o n i s
in flu e n c e d by tim e o f e s t r u s fo llo w in g tr e a tm e n t and e i t h e r bred a t 12
hr
a f t e r e s t r u s o r a t 80 h r ( a p p o in tm e n t b re d ); 4) t o d e te r m in e th e
d i s t r i b u t i o n o f e s t r u s i n s u c k le d b e e f cows a f t e r a s i n g l e PGF2ct
i n j e c t i o n s y s te m ; 5) t o co m p are a r t i f i c i a l i n s e m i n a t i o n p re g n a n c y
r a t e s and t o t a l pregnancy r a t e s i n a 50 day b reed in g sea so n i n su ck le d
b e e f cow s r e c e i v i n g e i t h e r h e a t d e t e c t i o n and i n s e m i n a t i o n 12 h r
a f t e r w a r d f o r 4.5 d a y s th e n a l l a n im a ls n o t d e t e c t e d by t h a t tim e
33
i n j e c t e d w ith PGFga and in s e m in a te d a f t e r d e t e c t e d e s t r u s f o r f o u r
m ore d a y s o r tw o i n j e c t i o n s o f PGFga 11 d a y s a p a r t and in s e m in a te d
o n ly a t 80 h r a f t e r t r e a t m e n t ; and 6) t o co m p are c a l v i n g r a t e s a t
v a rio u s s ta g e s o f th e seaso n in b e e f cows bred a f t e r e i t h e r a s in g le
PGFga i n j e c t i o n system or a double PGFga i n j e c t i o n system w ith an 11
day i n t e r v a l b e tw e e n .in je c tio n s .
M a te r ia ls and Methods
A n im a ls .
T h ree h e r d s
of
s u c k le d
beef
co w s
lo c a te d
in
th e
i n t e r m o u n t a i n r e g i o n o f M ontana w e re u s e d i n t h e s e s t u d i e s and
in c lu d e d :
H erd I ) 299 Angus and Angus x H e re fo rd co w s, 3 t o 5 y e a r s
o l d , a t th e Dana Ranch Company, C a sc a d e , M ontana; H erd I I ) 138 Angus
and Angus x H e re f o rd co w s,
E xperim ent S ta tio n ,
N o rris ,
2 to
10 y e a r s o ld ,
a t th e Red B l u f f
Montana; and Herd I I I ) 219 m o stly AngUs,
H e r e f o r d and H e re f o rd c r o s s cow s, 3 and 4 y e a r s o ld , a t th e M ontana
S t a t e P r is o n R anch, D eer L odge, M ontana.
A ll cow s w e re a t l e a s t 50
d a y s p o s t- p a r tu m w hen t r e a t m e n t s w e re i n i t i a t e d and w e re n u r s in g
c a lv e s .
T r i a l s and T re a tm e n ts.
T r ia l I.
Cows w i t h i n a h e rd w e re a s s ig n e d a t random to one o f
t h r e e t r e a t m e n t g ro u p s w h ic h in c l u d e d :
I) c o n t r o l s w h ic h w e re
a r t i f i c i a l l y i n s e m in a te d (A l) 12 h r a f t e r d e t e c t e d
re c e iv in g
tw o
in je c tio n s
o f L u ta ly s e ® (25
e s t r u s ; 2) cows
mg PGFga
fre e
a c id
3%
e q u iv a le n t)
11 d a y s a p a r t f o ll o w e d by i n s e m i n a t i n i o n 12 h r a f t e r
d e te c te d e s t r u s u n t i l 80 h r p o s t- tr e a tm e n t a t which tim e a l l cows n o t
y e t d e te c te d w ere in s e m in a te d (LL-A I-E-80); and 3) cows r e c e iv in g th e
same PGF2a tr e a tm e n t a s i n tr e a tm e n t 2 b u t in se m in a te d only a t 80 h r
p o s t-tre a tm e n t
(L L -A I-8 0 )
( f i g . 1 ).
T h is
tria l
in v o lv e d a l l
th e
e x p e rim e n ta l a n im a ls from a l l th r e e h e rd s.
T r i a l 2.
T h is t r i a l in v o lv e d o n ly th e e x p e r im e n t a l a n im a ls i n
Herds I I and I I I t h a t w ere a ss ig n e d to th e c o n tro l and LL-AI-80 groups
in t r i a l I.
The c o n t r o l a n im a ls i n t h e s e h e r d s w e re d e t e c t e d f o r
e s t r u s and i n s e m in a te d 12 h r a f t e r w a r d f o r 4.5 d a y s and a l l m em bers
n o t d e te c te d up to t h a t tim e re c e iv e d a s in g le i n j e c t i o n o f L u taly se ^
and d e t e c t i o n o f e s t r u s and i n s e m i n a t i o n c o n tin u e d f o r 4 m ore d a y s
(A I-L-A I-E).
The LL-AI-80 group i n t r i a l 2 c o n s is te d o f th e same LL-
AI-80 cows from th e s e two herds, i n t r i a l T ( f ig . 2).
D e te c tio n o f e s t r u s and b re e d in g .
A ll cows w ith in a h erd w ere r e ta in e d i n th e same f o o t h i l l p a s tu re
d u rin g th e Al season.
O b se rv a tio n s f o r e s t r u s began im m e d ia te ly a f t e r
th e second PGF2a i n j e c t i o n f o r a l l g ro u p s and w ere ex ecu ted by tra in e d
t e c h n i c i a n s a t l e a s t tw ic e d a i l y f o r p e r i o d s o f one h o u r o r m ore
d u rin g th e e a r ly m orning and evening h o u rs.
s ta n d in g to be mounted by herdm ates.
E s tru s was i d e n t i f i e d as
E s tru s was re c o rd e d f o r members
o f a l l g ro u p s i n e a c h h e r d d u r in g t h e i r r e s p e c t i v e Al s e a s o n .
S in c e
35
th e LL-A I-E-80
and
LL-AI-80
PGFga t r e a t m e n t t h e i r
groups
e s tru s
d a ta
in
tria l I
w e re
re c e iv e d th e same
c o m b in e d
to
d e riv e
a
d i s t r i b u t i o n o f o n s e t o f e s tr u s a f t e r t h i s tre a tm e n t. . A d i s t r i b u t i o n
o f o n s e t o f e s t r u s i n th e c o n tr o l group i n t r i a l I was ta b u la te d f o r a
fo u r-d a y p e rio d .
A d i s t r i b u t i o n o f e s tr u s i n th e A I-L-AI-E group i n
t r i a l 2 was ta b u la te d f o r th o se a n im a ls re c e iv in g PGFga .
The
sa m e
tra in e d
te c h n ic ia n s
in s e m in a tio n s i n a l l th r e e h e rd s.
p e rfo rm ed
th e
a rtific ia l
A ll cows t h a t w ere bred i n re g a rd
to e s t r u s w ere a r t i f i c i a l l y in s e m in a te d 12 h r a f t e r they w ere d e te c te d
in e s tru s .
Cows i n th e L L -A I-E -8 0 and L L -A I-80 g ro u p s t h a t w e re
d e te c te d i n e s t r u s a f t e r 96 h r post-PGFga (16 h r a f t e r 80 h r b reed in g )
w ere re in s e m in a te d 12 h r a f t e r d e te c te d e s tr u s w ith semen from a b u ll
o f a b reed d i f f e r e n t from t h a t used a t th e 8 0 -h r b re e d in g to p ro v id e a
g e n e t i c m a rk e r to d e te r m in e s i r e o f c a l f .
In H erd I , B la c k Angus
sem en w as u s e d i n t h e c o n t r o l cow s and i n th e P G F g ^ -tre a te d cow s
th ro u g h th e 80 h r b r e e d in g .
P o ll e d H e re f o rd sem en w as u s e d f o r th e
second in s e m in a tio n s i n th e cows t h a t w ere tr e a te d .
The Al seaso n was
6 days f o r t h i s h e rd and B lack Angus c le a n -u p b u lls fo llo w e d .
II,
In Herd
f i r s t in s e m in a tio n s w ere w ith T a re n ta is e semen i n a l l groups f o r
both t r i a l s .
Second in s e m in a tio n s w ere w ith P o lle d H erefo rd semen i n
Angus cows and S h o rth o rn semen i n th e H erefo rd x Angus cows.
The Al
s e a s o n w as 8.5 d a y s i n t h i s h e rd and B la c k Angus c le a n - u p b u l l s
fo llo w e d .
In Herd I I I , f i r s t in s e m in a tio n s i n th e LL-AI-E-80 and LL-
36
A l-80 g roups w ere w ith P o lle d H erefo rd semen.
Second in s e m in a tio n s i n
th e s e groups w ere w ith B lack Angus o r Longhorn semen.
C o n tro l cows i n
t r i a l I (AI-L-AI-E i n t r i a l 2) w ere in s e m in a te d w ith e i t h e r Longhorn
o r P o ll e d H e re f o rd sem en.
The Al s e a s o n w as 8.5 d a y s and B rahm an
c r o s s , Red A ngus, B la c k Angus and H e r e f o r d c le a n - u p b u l l s f o llo w e d .
C le a n -u p b u l l s w e re i n t r o d u c e d a b o u t 12 h r a f t e r th e l a s t Al i n a l l
h e rd s .
These h e rd s w ere th e n moved to m ountain summer p a s tu r e s and
b u lls rem ained w ith th e cows u n t i l th e end o f a 50-day b re e d in g seaso n
(Al p lu s n a tu r a l s e r v ic e ) .
S t a t i s t i c a l A n aly ses.
O nset o f e s t r u s ,
b re e d in g and c a lv in g re c o rd s s u p p lie d th e d a ta
f o r th e s e t r i a l s .
T r ia l I.
C u m u la tiv e Al p re g n a n c y r a t e s
(num ber o f a n im a ls
p r e g n a n t f num ber i n g ro u p ) f o r th e f i r s t f o u r d a y s o f th e b r e e d in g
s e a s o n w e re u s e d to c o m p are s y s te m s .
C a lv in g and b r e e d in g r e c o r d s
w e re u s e d to d e te r m in e th e s i r e o f th e c a l f (A l v e r s u s c le a n - u p ) and
th e g e n e tic m arkers w ith in a herd w ere th e main c r i t e r i a .
G e sta tio n
l e n g t h s o f 286 d a y s f o r H e re f o rd and H e re f o rd c r o s s , 281 d a y s f o r
Angus and 283 days f o r o th e r b reed s w ere used when g e n e tic m arkers d id
n o t s a t i s f a c t o r i l y d e te rm in e the s i r e .
O ther c r i t e r i a such as b i r t h
w e ig h t and sex o f c a l f along w ith ob serv ed h e a ts and an av erag e 21 day
e s tr o u s c y c le f o r cows, w ere a ls o in c o rp o ra te d .
37
I n i t i a l l y , in d iv id u a l d a ta a n a ly s is f o r each h erd was perform ed.
C o n tin g e n c y C h i-s q u a re ( S t e e l and T o r r i e , 1976) w as u s e d to a n a ly s e
d if f e r e n c e s among tr e a tm e n ts and to combine o n s e t o f e s t r u s d a ta among
h e rd s.
A l o g - l i n e a r m odel f o r a t t r i b u t e d a t a ( F ie n b e r g , 1977) was
used to t e s t f o r h erd x tre a tm e n t i n t e r a c t i o n to combine th e pregnancy
ra te d a ta .
T r i a l 2.
F i r s t s e r v ic e Al pregnancy r a t e s d u rin g th e 8.5 day Al
sea so n w ere compared betw een sy stem s.
C um ulative c a lv in g r a t e s by 17,
38 and 60 d a y s o f c a l v i n g w e re co m p u ted and co m p ared .
i n t e r v a l s b eg an on th e day th e f i r s t c a l f was b o rn .
C a lv in g
A llo w a n c e f o r
v a r i a t i o n among in d iv id u a ls o f seven days g e s ta tio n was in c o rp o ra te d
to ap p ro x im ate c a lv in g from pregnancy i n th e f i r s t 10, 31 and >50 days
o f b r e e d in g .
re c o rd s .
T hese w e re d e te r m in e d th ro u g h b r e e d in g and c a lv i n g
C ontingency C h i-sq u are was used f o r s t a t i s t i c a l a n a ly s e s o f
th e s e d a ta and a le v e l l e s s th a n 5% was c o n sid e re d s i g n i f i c a n t .
R e s u lts
T r ia l I.
T he.num ber o f cow s i n b o th th e c o n t r o l and com bined
PGFga - tr e a te d groups f o r th e th re e h e rd s i n t h i s stu d y a re d e p ic te d
in ta b le I.
P e r c e n ta g e d i s t r i b u t i o n s o f e s t r u s a f t e r f o u r d a y s o f
d e t e c t i o n i n th e co m b in ed h e r d s a r e show n i n f i g u r e 3«
T h rity -fo u r
p e rc e n t o f th e PGFga - ^ e a t e d cows and 17$ o f th e c o n tr o l cows (P<.05)
w e re o b s e r v e d i n e s t r u s d u r in g t h i s p e r io d .
T h e r e f o r e , t h i s d o u b le
38
i n j e c t i o n tre a tm e n t was e f f e c t i v e i n s y n c h ro n iz in g e s tr u s .
B e h a v io ra l e s t r u s o c c u rre d i n th e double in je c te d cows through a t
l e a s t day 6 p o s t- tr e a tm e n t.
in
th e
PGF2ot- t r e a t e d
The combined h e rd s d i s t r i b u t i o n o f e s tr u s
cow s ( f i g .
4) d e m o n s t r a t e s
th a t
th e re
is
v a r i a t i o n o f a t l e a s t 5 d a y s (d a y s 2 -6 ) i n th e i n t e r v a l fro m t h i s
tr e a tm e n t to o n s e t o f e s tr u s i n b e e f cows.
Two h u n d re d -e ig h te e n (50%)
o f th e s e a n im a ls w ere d e te c te d d u rin g t h i s 5-day p e rio d .
The m a jo rity
(58%) o f t h e s e w e re d e t e c t e d on day 3 o r 4 f o l l o w i n g t r e a t m e n t .
A n o th e r 32% w e re d e t e c t e d on day 5 o r 6, w h ile 10% w e re o b s e r v e d on
day 2.
O b s e r v a tio n s f o r e s t r u s c o n tin u e d f o r 2.5 m ore d a y s i n H erds
I I and I I I .
Only 3 (1.3%) o f th e s e
a n im a ls w ere d e te c te d d u rin g t h i s
p e rio d and th e s e w ere a l l in Herd I I I and w ere d e te c te d on day 7.
C alving re c o rd s f o r 53 and 29 o f th e e x p e rim e n ta l cows i n Herds I
and I I I , r e s p e c t i v e l y , w e re u n a v a i l a b l e a f t e r th e c a l v i n g s e a s o n .
T h ese l o s s e s w e re a t t r i b u t e d m o s tly t o m i s i d e n t i f i c a t i o n o f cows
TABLE I.
COW DISTRIBUTION BY HERD AND GROUP IN THREE HERDS
OF SUCKLED BEEF COWS RECEIVING TWO INJECTIONS OF
PGF2a 11 DAYS APART
C o n tro l
T reated
T o ta l
Herd I
Herd I I
Herd I I I
103
47
74
196
91
145
299
138
219
T o ta l
224
432
656
Herd
39
e i t h e r a t c a lv in g o r d u rin g s o r tin g o f e x p e rim e n ta l members from t h e i r
h e r d m a te s
p rio r
to
c a lv in g .
T h ese
in d iv id u a ls
w e re
ra n d o m ly
d i s t r i b u t e d among tr e a tm e n t groups and w ere d e le te d from th e f e r t i l i t y ,
d a ta .
C um ulative pregnancy r a t e s from Al d u rin g th e f i r s t fo u r days o f
th e b re e d in g seaso n a re shown i n ta b l e 2.
C um ulative pregnancy r a t e
e q u a ls th e number o f a n im a ls p re g n a n t d iv id e d by th e number o f an im als
i n th e g ro u p .
I n th e a n a l y s i s o f a l l t h r e e h e r d s and th e com bined
h e r d s t h e r e w as a h i g h e r (P<.05) 4 -d a y p re g n a n c y r a t e i n t h e t r e a t e d
groups th an i n th e c o n tr o ls .
R e s u lts from Herds I and I I in d ic a te d a
tre n d f o r a h ig h e r 4-day pregnancy r a t e i n th e LL-AI-E-80 group th an
i n th e LL-AI-80 group a lth o u g h th e d i f f e r e n c e s w e re n o t s i g n i f i c a n t
(P > .0 5 ).
The r e v e r s e t r e n d was n o te d i n H erd I I I .
H erd x t r e a t m e n t
i n t e r a c t i o n a n a l y s i s a p p ro a c h e d s i g n i f i c a n c e (P < ,09).
T h is r e v e a l s
t h a t t h e r e w as a te n d e n c y f o r h e r d s t o re s p o n d d i f f e r e n t l y t o t h e s e
b re e d in g management sy ste m s, but t h i s d if f e r e n c e was n o t pronounced.
C a lf p ro d u c tio n from a r t i f i c i a l in s e m in a tio n was n o t d i f f e r e n t (PX05)
betw een th e s e two b re e d in g sy stem s i n th e combined h e rd s .
Of th o s e cow s o b s e r v e d i n e s t r u s d u r in g th e f i r s t f o u r d ay s o f
d e te c tio n ,
th e pregnancy r a t e s (number o f cows p re g n a n t ^ number o f
cow s o b s e r v e d i n e s t r u s ) d id n o t d i f f e r (P > .05). D i f f e r e n c e s among
g ro u p s w e re n o te d i n p re g n a n c y r a t e w i t h i n th o s e 1 2 -h r i n t e r v a l s o f
d e te c tio n in
w h ic h a t l e a s t one i n d i v i d u a l from a l l g ro u p s w as
40
o bserved i n e s tr u s .
84 -9 6 h r a f t e r
These i n t e r v a l s in c lu d e d 36-48, 48-60, 60-72 and
PGF2 a t r e a t m e n t .
W ith in th e L L -A I-80 g ro u p th e
pregnancy r a t e o f th o se a n im a ls d e te c te d i n e s tr u s rem ain ed c o n s ta n t
(P>.05) among th e 12-hr i n t e r v a l s i n which e s tr u s was d e te c te d .
The r e p ro d u c tiv e perform ance d u rin g th e 6-day d e te c tio n p e rio d o f
th e r e m a in in g t r e a t e d
cow s i s
show n i n t a b l e 4.
T h ese a n im a ls
i n c lu d e d th o s e n o t d e t e c t e d i n e s t r u s d u r in g t h i s p e r io d and th o s e
d e t e c t e d on day 5 o r 6.
None o f th e t r e a t e d a n im a ls i n e s t r u s on day
5 o r 6 w ere p re g n a n t from th e ap p o in tm en t b re e d in g .
A ll o f th e se cows
w e re r e p e a t - i n s e m i n a t e d a t 12 h r a f t e r b e in g d e t e c t e d and 71$ o f 28
L L -A I-E -80 cow s and 77$ o f 35 LL -A I-80 cow s w e re p r e g n a n t t o t h e s e
in s e m in a tio n s .
T hese p re g n a n c y r a t e s d id n o t d i f f e r (P > .05) e i t h e r
b e tw e e n t r e a t m e n t g ro u p s o r fro m
in s e m in a te d .
u n tre a te d
c o n tro ls
t h a t w e re
E ig h ty -se v e n o f th e LL-AI-E-80 cows and 97 LL-AI-80 cows
w ere n o t o bserved i n e s t r u s d u rin g th e 6-day d e te c tio n p e rio d and o f
th e s e ,
37 a n d 3 9 $ ,
re s p e c tiv e ly ,
(P > .0 5 ) w e re p r e g n a n t f r o m
in s e m in a tio n s a t th e ap p o in tm en t b re e d in g .
T r i a l 2.
T h i r t y - n i n e (83$) and 59 (88$) (P>.05) o f th e cow s i n
th e A I-L -A I-E g ro u p i n H erds I I and I I I , r e s p e c t i v e l y , w ere n o t
'
o b serv ed in
e s tru s
d u r in g th e f i r s t 4.5 d a y s o f d e t e c t i o n and
"
r e c e i v e d . PGF2 a ( t a b l e 5 ).
Of th o s e r e c e i v i n g PGF2a, 29 (74$) and 40
(68$) (PX05) i n Herds I I and I I I ,
r e s p e c tiv e ly , w ere d e te c te d d u rin g
th e fo llo w in g 4 days.
In th e combined h e rd s 58 (59$) o f th e in je c te d
cows w ere observed i n e s t r u s betw een 36 and 96 h r a f t e r PGF201 .
This
r e p r e s e n t s t h e p e ak p e r i o d o f e s t p u s i n t h i s g ro u p and d e m o n s t r a t e s
t h a t t h i s s y s te m i s e f f e c t i v e i n s y n c h r o n iz in g e s t r u s .
T h is a g r e e s
w ith Hafs j i i a l . , (1975a) who re p o rte d a peak re sp o n se betw een 48 and
120 h r P o st-P G F 2 a i n s u c k le d b e e f cow s a f t e r a s i n g l e i n j e c t i o n o f
PGF2<V
A com parison o f th e re p ro d u c tiv e perform ance o f th e s e cows in 8.5
days o f Al to t h a t o f t h e i r h erd m ates i n th e LL-AI-80 b re e d in g system
i s shown i n t a b l e 5.
The f i r s t Al pregnancy r a t e (number p reg n an t to
f i r s t Al T number r e c e iv in g f i r s t Al) was h ig h e r (P<.05) i n th e AI-LA I-E g ro u p th a n i n t h e L L -A I-80 g ro u p i n Herd I I I and t h e com bined
h e rd s.
The same tre n d was noted i n Herd I I bu t th e d if f e r e n c e was not.
s i g n i f i c a n t (P X 0 5 ).
T o t a l Al p re g n a n c y r a t e (num ber p r e g n a n t to
f i r s t Al r number i n group) was no t d i f f e r e n t (PX05) betw een groups
i n e i t h e r h erd o r th e combined h e rd s.
D isc u ssio n
The v a r i a t i o n i n th e i n t e r v a l from tre a tm e n t to o n s e t o f e s tr u s
fo u n d i n
(1975a).
t r i a l . I c o n c u r s w ith r e s u l t s
re p o rte d
by H a fs
a l.f
S ince PGF2 a does n o t a l t e r th e average tim e (24-32 hr) from
o n set of e s tru s
to o v u la tio n
( L o u i s e t a l . f 1974);, i t
may b e
h y p o th e siz e d t h a t th e lo w er th a n s a t i s f a c t o r y p ro d u c tio n from th e LL-
A I-80 s y s te m i s due to i n s e m i n a t i n g cow s to o e a r l y o r to o l a t e i n
r e l a t i o n to o v u la tio n .
Those cow s sh o w in g e s t r u s m ore th a n 20 h r
p r i o r t o t h e a p p o in tm e n t b r e e d in g w o u ld n o t be e x p e c te d t o c o n c e iv e
( a s r e v ie w e d by L a u d e r d a le , 1974).
T h ese d a t a ( t a b l e 3) show t h a t
i n s e m i n a t i n g a s l a t e a s 32 h r o r m ore a f t e r d e t e c t e d e s t r u s (cow s
d e te c te d d u rin g th e 36-48 h r p o s t- tr e a tm e n t i n t e r v a l ) s t i l l r e s u lte d
i n p re g n a n c y fro m th e a p p o in tm e n t b r e e d in g .
A lso , th o s e a n im a ls
in s e m i n a t e d b e tw e e n 20 and 32 h r a f t e r e s t r u s w e re p r e g n a n t a t th e .
sam e r a t e
as
th o s e in s e m in a te d
12 h r a f t e r o b s e r v e d e s t r u s .
C o n c e p tio n r a t e s t o i n s e m i n a t i o n s 24 h r a f t e r o b s e r v e d e s t r u s h a v e
b e e n r e p o r t e d t o e q u a l th o s e t o i n s e m i n a t i o n s 12 h r a f t e r e s t r u s i n
b e e f h e i f e r s (V incent and T u rn er, 1972) and d a iry cows (Gwasdaukas and
L in e w e a v e r1
1 9 8 1 ).
It
may b e
s u g g e s te d
th a t
fe rtility
to
in s e m in a tio n s a t 80 h r a f t e r t h i s PGF2ot tr e a tm e n t i s n o t a f f e c te d by
tim e o f o n s e t o f e s tr u s p r io r to t h i s ap p o in tm en t b re e d in g .
Four o f seven tr e a te d cows t h a t w ere observ ed i n e s tr u s betw een 4
and
16 h r a f t e r
in s e m in ia tio n .
th e a p p o in tm e n t b r e e d in g w e re p r e g n a n t t o t h a t
T his pregnancy r a t e was n o t d i f f e r e n t from t h a t e i t h e r
i n cow s w h ic h w e re i n e s t r u s p r i o r t o th e a p p o in tm e n t b r e e d in g a t
w h ic h th e y w e re b re d o r i n cows b re d by e s t r u s .
S im ila r r e s u l t s in
p r o g e s to g e n s y n c h r o n iz e d cow s w e re r e p o r t e d by C a r r ic k and S h e lto n
(1 967).
T h ir ty - e ig h t p e rc e n t o f th e tr e a te d cows (70 o f 184) which w ere
43
n o t d e te c te d i n e s t r u s d u rin g th e d e te c tio n p e rio d w ere p re g n a n t from
th e a p p o in tm en t b re e d in g .
These a n im a ls may have e i t h e r f a i l e d to be
d e t e c t e d o r o v u la te d w ith o u t b e h a v i o r a l e s t r u s (D o n a ld so n , 1977).
Most o f th e d e te c tio n f a i l u r e s ,
i f th ey d id o ccu r,
may have r e s u lte d
due t o m ass h a n d lin g o f th e h e r d s d u r in g t h e a p p o in tm e n t b r e e d in g .
T h is
c o u ld
have
p r e v e n te d
b e h a v io ra l e s tr u s .
th e
e s tru s
a n im a ls
fro m
d is p la y in g
A lso , th e a t t e n t i o n o f th e t e c h n i c i a n s a t t h i s
tim e was tow ard in s e m in a tin g and away from d e te c tin g .
B ut, th e s t r e s s
o f h a n d lin g p r o b a b ly w ould n o t h a v e p r e v e n te d p h y s i o l o g i c a l e s t r u s
(V/agnon, £fc. aL ,, 1972; Mawhinney and Roche, 1980).
C onversely, H ardin
e t a l . . (1980) c ite d evidence t h a t tim ed in s e m in a tio n s co u ld su p p re ss
b e h a v io ra l e s tr u s by s tim u la tin g a p re m a tu re r e le a s e o f p re o v u la to ry
LH r e s u l t i n g
in
an i n h i b i t i o n
of fo llic u la r
n e c e s s a r y f o r t h i s b e h a v io r to o c c u r .
e s tro g e n s e c r e tio n
L a u d e r d a le
& !., (1974) and
B u r f e n in g s Jl SJL.* (1978) o b s e r v e d t h a t some cow s becom e p r e g n a n t
w ith o u t e x h ib itin g e s t r u s when bred by ap p o in tm en t a f t e r PGF2ct.
I f th e Al pregnancy r a t e o f th e s e u n d e te c te d a n im a ls i s s im ila r
to t h a t o f th e u n tre a te d c o n tr o ls (69%), th e n a p p ro x im a te ly 100 o f th e
u n d e te c te d tr e a t e d a n im a ls o v u la te d w ith o u t being d e te c te d i n e s tr u s .
F u r th e r m o r e , i f a l l cow s d e t e c t e d d u r in g th e 6 -d a y p e r io d d id so i n
re sp o n se to th e tr e a tm e n t (99 LL-AI-1-80 p lu s 92 LL-A l-80,
191 t o t a l )
th e n th e tw o i n j e c t i o n PGF2a t r e a t m e n t w as e f f e c t i v e on 78$ (291 o f
375) o f th e tr e a te d cows.
44
The d i f f e r e n c e , i n f i r s t Al p re g n a n c y r a t e i n t r i a l 2 i n d i c a t e s
t h a t th e e f f ic ie n c y o f th e AI-L-AI-E system i s b e t t e r th a n th e LL-AI80 system i n te rm s o f th e amount o f semen needed to a c q u ir e th e same
num ber o f Al c a l v e s ( t o t a l Al p re g n a n c y r a t e , P>.05)«
days o f h e a t d e te c tio n w ere n e c e ssa ry to do t h i s .
n o t u s e d i n th e L L -A I-80 s y s te m .
H ow ever, 8.5
H eat d e te c tio n was
The am ount o f d ru g u s e d i n th e LL-
A I-8 0 s y s te m was 122% m ore th a n t h a t u s e d i n t h e A I-L -A I-E s y s te m .
The n e t r e s u l t i s an e q u al number o f Al c a lv e s from e i t h e r sy stem , b u t
t h e t r a d e - o f f s a r e m ore d ru g and sem en f o r l e s s tim e and la b o r f o r
d e te c tin g e s t r u s .
One p o s s ib le advantage o f th e two i n j e c t i o n system i s i l l u s t r a t e d
i n ta b l e 7.
S ig n i f ic a n tl y more c a lv e s w ere born d u rin g th e f i r s t 38
days o f c a lv in g i n th e LL-AI-80 system th a n i n th e A I-L-AI-E system in
H erd I I I and th e co m b in e h e r d s .
d i f f e r e n t was no ted i n Herd I I .
A s im ila r
tre n d ,
a lth o u g h n o t
T his added gro u p in g e f f e c t a t c a lv in g
adds m e r it to th e LL-AI-80 system .
J a c k s o n s Jl a l . ,
(1979) re v ie w e d and s u p p o r te d e v id e n c e t h a t
e s t r u s and o v u la tio n a f t e r a s in g le PGF2 a i n j e c t i o n in d i e s t r u s cows
v a rie d
o v e r a w id e r ra n g e
in je c tio n s
11 d a y s a p a r t .
th a n
T hus,
e s tru s
and o v u l a t i o n a f t e r
th e c l o s e r
tw o
g r o u p in g e f f e c t o f
c a lv in g i n th e LL-AI-80 system th a n i n th e AI-L-AI-E system may have
r e s u l t e d from more a n im a ls having a t l e a s t two o p p o r tu n itie s to become
p r e g n a n t and c a lv e w i t h i n th e f i r s t 38 d a y s i n t h e d o u b le i n j e c t i o n
45
s y s te m .
T h o s e .in d iv id u a ls
th a t
re sp o n d ed
la te r
in
th e
s in g le
i n j e c t i o n s y s te m may n o t h a v e h ad a n o t h e r o p p o r t u n i t y to becom e
p re g n a n t and c a lv e d u rin g t h i s i n t e r v a l i f t h e i r c y c le le n g th was a t
th e ex trem e end o f th e av erag e 17 to 24 day i n t e r v a l . .
The r e p ro d u c tiv e e f f ic ie n c y o f t r e a t e d groups i n e i t h e r tif th e se
s t u d i e s w as n o t h ig h ( a p p r o x im a te ly 50% t o t a l Al p re g n a n c y r a t e ) .
Some im p ro v e m e n ts i n e f f i c i e n c y
may r e s u l t fro m m ore c r i t i c a l l y
s e le c tin g c a n d id a te s f o r th e s e b re e d in g management sy ste m s.
W iltbank
(1970) r e v ie w e d e v id e n c e t h a t i n d i c a t e maximal c o n c e p tio n r a t e s a re
o b ta in e d when b e e f cows a re a t l e a s t 60 days p o st-p a rtu m .
The a n im a ls
used i n th e s e s tu d ie s w ere 50 or more days p o stp artu m .
Some m o d i f i c a t i o n o f e i t h e r s y s te m i n t r i a l 2 may y i e l d m ore
s a tis fa c to ry re s u lts .
D o n a ld so n (1980) re p o rte d t h a t th e e f f ic ie n c y
o f an AI-L-AI-E system i n which cows w ere d e te c te d and in se m in a te d f o r
5 days p r i o r to th e r e s id u a l PGF2a tr e a tm e n t and in s e m in a te d f o r a 10
day t o t a l p e rio d was e q u al to th e e f f ic ie n c y o f in s e m in a tin g u n tre a te d
c o n tr o ls f o r 21 days.
In t h i s stu d y a 4.5 day p re tre a tm e n t p e rio d and
an 8.5 day t o t a l Al p e rio d were used.
More Al c a l v e s may be a c q u ir e d i n t h e L L -A I-80 s y s te m by h e a t
d e te c tin g arid r e p e a t in s e m in a tin g t r e a t e d cows betw een 96 and 144 h r
a f t e r tre a tm e n t.
The f a i l u r e o f a n im a ls showing e s t r u s d u rin g t h i s
p e rio d to become p re g n a n t to th e ap p o in tm en t b re e d in g i s d e m o n strated
i n t r i a l I ( t a b l e 4 ).
The f e r t i l i t y o f t h e s e a n im a ls t o th e r e p e a t .
46
in s e m in a tio n s i s
a t l e a s t a s good a s t h a t i n u n t r e a t e d c o n t r o l s
in s e m in a te d a f t e r d e te c te d e s tr u s ,
20% m ore sem en ( f i g .
4 ).
T his pro ced u re would r e q u ir e 15 to
I f c le a n - u p b u l l s a r e u s e d im m e d ia te ly
fo llo w in g th e ap p o in tm en t b re e d in g th ey sh o u ld n o t be in tro d u c e d u n t i l
a t le a s t
16 h r l a t e r .
Cows t h a t show e s t r u s up t o t h a t tim e do
co n ceiv e to th e ap p o in tm en t b re e d in g .
C on clu sio n s
Two i n j e c t i o n s o f 25 mg PGFgg, Tl d a y s a p a r t d o e s s y n c h r o n iz e
e s t r u s i n s u c k le d b e e f cow s w h ic h a r e a t l e a s t 50 d a y s p o s t p a rtu m .
There i s a v a r i a t i o n i n th e i n t e r v a l from tre a tm e n t to o n s e t o f e s tr u s
o f a t l e a s t 5 d a y s (d a y s 2 th ro u g h 6 p o s t - t r e a t m e n t ) .
The p re g n a n c y
r a t e fro m a r t i f i c i a l i n s e m i n a t i o n a d m i n i s t e r e d e i t h e r 12 h r a f t e r
d e t e c t e d e s t r u s up t o 80 h r p o s t - t r e a t m e n t th e n a l l a n im a ls n o t y e t
i n s e m in a te d a r e i n s e m in a te d a t t h i s tim e o r o n ly a t 80 h r p o s t ­
tre a tm e n t i s n o t d i f f e r e n t fo llo w in g t h i s double i n j e c t i o n tre a tm e n t.
T his i s because pregnancy r a t e from an 80 h r ap p o in tm en t b re e d in g i n
s u c k le d b e e f cow s i s n o t i n f l u e n c e d by tim e o f o n s e t o f e s t r u s t h a t
o c cu rs b e fo re 96 h r p o s t- tr e a tm e n t.
T h e re fo re , an 80 h r app o in tm en t
b re e d in g sh o u ld be used a f t e r t h i s double i n j e c t i o n PGF2a tre a tm e n t i n
su c k le d b e e f cows and h e a t d e te c tio n up to 96 h r p o s t- tr e a tm e n t i s n o t
r e q u ire d ; a ls o , some cows become p re g n a n t to t h i s in s e m in a tio n w ith o u t
d is p la y in g e s tr u s
th ro u g h a 6 -d a y p o s t - t r e a t m e n t p e r i o d .
T hose
47
a n im a ls t h a t show e s t r u s a f t e r 96 h r p o s t - t r e a t m e n t do n o t becom e
p re g n a n t t o an 80 h r b re e d in g .
I f c a lv e s from a r t i f i c i a l in s e m in a tio n
a r e d e s ir e d from th e s e a n im a ls i t i s n e c e ssa ry to re in s e m in a te th e s e
cows a f t e r b e in g d e te c te d i n e s tr u s .
T h is r e in s e m in a tio n p e rio d would
l a s t o n ly a b o u t 48 h r and a p p r o x im a te ly 20% m ore sem en w ould be
re q u ire d .
A s y s te m i n v o l v i n g d e t e c t i n g e s t r u s f o r 4.5 d a y s th e n
i n j e c t i n g a l l cow s n o t y e t d e t e c t e d and d e t e c t i n g e s t r u s f o r 4 m ore
d a y s show s t h a t e s t r u s i n s u c k le d
beef
cow s, ( a t
le a s t
50 d a y s
p o stp artu m ) i s sy n ch ro n ized w ith one i n j e c t i o n o f 25 mg PGF2 a .
There
i s no d i f f e r e n c e i n th e num ber o f c a l v e s p ro d u c e d fro m a r t i f i c i a l
i n s e m i n a t i o n when b e e f cow s a r e e i t h e r i n s e m in a te d
12 h r a f t e r
d e te c te d e s t r u s i n t h i s s in g le i n j e c t i o n system o r in s e m in a te d w ith o u t
re g a rd to e s t r u s a t 80 h r a f t e r two i n j e c t i o n s o f PGF2a a d m in is te re d
11 d a y s a p a r t .
The c h o ic e b e tw e e n w h ic h o f t h e s e
tw o b r e e d in g
management sy ste m s to use on su ck le d b e e f cows sh o u ld be based on th e
am ount o f tim e , p a s t u r e and l a b o r a v a i l a b l e f o r d e t e c t i n g e s t r u s a s
opposed th e e x tr a c o s t f o r more drug and semen n e c e ssa ry to a l l e v i a t e
th e s e re q u ire m e n ts.
One p o s s i b l e a d v a n ta g e o f t h e d o u b le i n j e c t i o n PGF2a s y ste m i s
t h a t m ore c a l v e s a r e b o rn i n th e f i r s t 38 d a y s o f c a l v i n g f o l l o w i n g
t h i s t r e a t m e n t th a n f o l l o w i n g t h e s in g le i n j e c t i o n tr e a tm e n t.
This
adds m e r it to th e LL-AI-80 system because more c a lv e s i n a group would
be s i m i l a r i n age.
APPENDIX
Controls
R esid u al PGF
(Herd I I
and I I I ) i
Al a n d (o r) c le a n -u p b u lls
d e te c t
AM' PM AMlPM AM PM AMIPM AM!PM AM;PM AMlPM AMiPM AM!PM
Day o f b re e d in g seaso n
LL-A l - E—80
heat
d e te c t
AM!PM
R esid u al
80 h r
b re e d in g
Al a n d (o r) c le a n -u p b u lls
AMlPM AMlPM AMlPM AMlPM AMlPM AMI PM I AMI PM AMI PM
AMlPM
Day o f b re e d in g seaso n
LL-AI-8Q
1 st
PGF2 a
in j.
AMI PM / /
-11
2nd
PGF2 a
in j.
80 h r
appointm ent
b re e d in g
Al a n d (o r) c le a n -u p b u lls
i____________________ ______ |______________
AMI PM amI pm amI pm amIpm amI pm amI pm amI pm am I pm am I PM am| pm
0
4
2
6
8
I
5
7
3
9
Day o f b re e d in g seaso n
F ig u re I .
D esign o f b re e d in g management system s in t r i a l I
n
AI-L-AI-E
heat
d e te c t
AM IPM
L ast
R esid u al
PGFga
in je c tio n
AM IPM AMIPM am Ipm am !pm Sam !pm
C lean-up
AM IPM AMIPM AMIPM AMIPM
Day o f b re e d in g seaso n
LL-AI-80
1 st
PGFga
in j.
2nd
pGF2CX
in j.
AMIPM
//
-11
am Ipm
0
80 h r
appointm ent
b re e d in g I_
Al a n d (o r) c le a n -u p b u lls
AMIPM am Ipm AMIPM am Ipm am Ipm am Ipm AMIPM am Ipm AMIPM
8
4
6
I
2
5
7
9
3
Day o f b re e d in g seaso n
F ig u re 2.
D esign o f b re e d in g management system s in t r i a l 2
-//-
bu
50 -
f/y /y /y j C o n tro l (n=224)
45
40 •-
PGF2a (*=432)
S . E.
P e rc e n t d e te c te d
35 ■30 -25 ■20
- -
15 •10
• -
d e te c tio n
F ig u re 3.
P e rc e n t d i s t r i b u t i o n (means ± S .E .) o f e s t r u s in c o n tr o ls and
cows re c e iv in g two i n j e c t i o n s o f PGF2a 11 days a p a r t i n th r e e
h e rd s o f su ck le d b e e f cows.
50 T
45 -S. E.
I
P e rc e n t d e te c te d
40 --
in j.
Day o f d e te c tio n
F ig u re 4.
P e rc e n t d i s t r i b u t i o n (means + S.E.) o f e s tr u s i n th re e h e rd s
o f su ck le d b e ef cows r e c e iv in g two i n j e c t i o n s o f PGF2a (25 mg) 11
days a p a r t (n = 4 3 2 ).
53
TABLE 2.
CUMULATIVE Al PREGNANCY RATES BY DAY FOUR OF BREEDING SEASON
FOLLOWING UNTREATED CONTROL, LL-AI-E-SO AND LL-AI-80#
B reeding Management System s00
Herd I
Number o f anim als
Number observed i n e s t r u s
Number p re g n a n t
C um ulative Al pregnancy r a t e
Herd I I
Number o f anim als
Number observed i n e s tr u s
Number p re g n a n t
C um ulative Al pregnancy r a t e
C o n tro l
LL-AI-E-80
87
20
11
79
23
IBga
4 lg b
47
7
6
46
25
30.
65.gb
IBga
3 2 K
Herd I I I
Number o f anim als
Number o bserved i n e s tr u s
Number p re g n a n t
C um ulative Al pregnancy r a t e
67
8
7
61
24
'IOfa
36gb
Combined h e rd s
Number o f anim als
Number observed i n e s tr u s
Number p re g n a n t
C um ulative Al pregnancy r a t e
210
35
24
12ga
186
71
84.
45gb
2 2 K
LL-AI-80
80
—
2 2 K
28gb
45
——
2 2 K
49gb
64
2K
45gb
189
'■ « =
73
39gb
“ C u m u la tiv e Al p re g n a n c y r a t e e q u a ls num ber o f a n im a ls p r e g n a n t 7
number o f anim als i n group.
“ “Herd x tre a tm e n t i n t e r a c t i o n (P < .0 9 )•
a ,b Means w ith d i f f e r e n t s u p e r s c r ip ts w ith in rows a r e s i g n i f i c a n t l y
d i f f e r e n t (P < .0 5 ).
TABLE
3.
PREGNANCY RATES OF COWS DETECTED IN ESTRUS DURING THE FIRST FOUR DAY
DETECTION FOLLOWING UNTREATED CONTROL, LL-A I-E-80 AND LL-AI-801
B reed in e Manaeement Svstems
T o tal
I
-1 2
- 24
- 36
- 482
- 602
- 722
- 84
- 962
LL-AI-
O
0
12
24
36
48
60
72
84
CO
LL-AI-E
C o n tro l
In te rv a l a f te r
PGF^_ (h r)
P ree n a n t
D etected
3
6
5
2
6
5
2
6
-I
4
3
2
3
4
2
5
0
0
I
13
33
19
I
4
0
0
I
. 7
26
15
■I
2
0
0
0
6
36
12
0
3
35
24
'7 1
52
57
D e tec te d
P ree n a n t
D etected
T o ta l pregnancy
7^
ra te 2
6Q*
1Pregnancy r a t e e q u a ls number o f cows p re g n a n t - number o f cows d e te c te d .
2Pregnancy r a t e s among system s 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 (P X 0 5 ).
3Pregnancy r a t e s among i n t e r v a l s were 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 (P X 0 5 ).
P re
61%
TABLE
4.
PREGNANCY RATES OF COWS EITHER DETECTED IN ESTRUS ON DAYS FIVE OR SIX OR
DETECTED DURING THE FIRST SIX DAYS OF THE DETECTION PERIOD FOLLOWING
LL-A I-E-80 AND LL-AI-80 1
B reeding Management Systems
LL-AI-80
LL-A I-E-80
Number
of
cows
E s tru s (day 5 o r 6)
Herd I
Herd I I
. Herd I I I
T o ta l
Pregnancy r a t e 2
11
8
9
28
Not d e te c te d (6 days)
Herd I
45 .
Herd I I
14
. Herd I I I
28
T o ta l
87
Pregnancy r a t e 2
Number
p re g n a n t
to 80 h r
b re e d in g
Number
p re g n a n t
to r e p e a t
b re e d in g
Number
of
cows
Number
p re g n a n t
to 80 h r
b re e d in g
0
0
0
0
8
6
6
20
71?
13
17
5
R5
0
0
0
0
13
10
9
32
37%
—
53
10
34
.97
13
8
17
18
39?
—
1Pregnancy r a t e e q u a ls number o f an im als p re g n a n t f number o f cows.
2Pregnancy r a t e s were 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 between system s (P > .0 5 ).
Num
p reg n
to re p e
b re e d i
11
11
5
27
77?
— —
«OCB
56
TABLE 5.
ESTRliS IN TWO HERDS OF SUCKLED BEEF COWS RECEIVING THE
A I-L-AI-E BREEDING MANAGEMENT SYSTEM
Number o bserved i n 4 .5
days (b e fo re PGF2a) 1
Number r e c e iv in g PGF2 a 1
Herd I I
(n=il7)
Herd I I I
(n-67)
8 (17)
8 (12)
16 (14)
39 (83)
59 (88)
98 (86)
I
0
2
7
7
5
3
4
29
0
2
6
7
13
6
I
5
40
I
2
8
14
20
11
4
Q
69
37 (79)
48 (72)
85 (75)
Combined
In = Iim
Number observed d u rin g i n t e r v a l
o f d e te c tio n a f t e r PGF2a (h r)
0 -1 2
12 - 24
2 4 -3 6
36 - 48
48- 60
60 - 72
72-84
84 - 06
T o ta l
.
T o ta l o bserved i n 8 .5 d a y s 1
1Numbers i n p a re n th e s e s eq u al p ercen t; o f t o t a l a n im a ls.
57
TABLE 6 .
COMPARISON OF TWO BREEDING MANAGEMENT SYSTEMS USED FOR
8 .5 DAYS OF ARTIFICIAL INSEMINATION1
B reeding Management Systems
AI-L-AI-E
LL-AI-80
Herd I I
Number o f anim als
Number in sem in ate d
Number p re g n a n t t o f i r s t Al
F i r s t Al pregnancy r a t e 1
T o ta l Al pregnancy r a t e 2
47
37
25
68%
53%
45
45
22
49%
49%
Herd I I I
Number o f anim als
Number in sem in ate d
Number p re g n a n t to f i r s t Al
F i r s t Al pregnancy r a t e
T o ta l Al pregnancy r a t e
67
. 48
33a
69%*
49%
64
64
29
45%b
45%
Combined h e rd s
Number o f anim als
Number in se m in a te d
Number p re g n a n t to f i r s t Al
F i r s t Al pregnancy
T o ta l Al pregnancy r a t e
114
85
58
68%a
51%
109
109
51h
47%b
47%
1F i r s t Al pregnancy r a t e e q u a ls number o f anim als p re g n a n t t o f i r s t
Al 7 number o f anim als in s e m in a te d .
2T o ta l Al pregnancy r a t e e q u a ls number o f a n im a ls p re g n a n t t o f i r s t
Al 7 numbr o f a n im a ls i n system .
a ^M eans w ith d i f f e r e n t s u p e r s c r i p t s w i t h i n rows a r e s i g n i f i c a n t l y
d i f f e r e n t (P < .0 5 ).
58
TABLE 7.
CUMULATIVE CALVING RATES AT VARIOUS STAGES OF THE CALVING
SEASON FOLLOWING TWO DIFFERENT BREEDING MANAGEMENT SYSTEMS0
B reeding Management Systems
AI-L-AI-E
Herd I I
Number o f anim als
C alving r a t e :
i n 17 days
i n 38 days
i n 60 days
Herd I I I
Number o f anim als
C alving r a t e :
i n 17 days
i n 38 days
i n 60 days
Combined h e rd s
Number, o f anim als
C alving r a t e :
i n 17 days
i n 38 days
i n 60 days
■ LL-A l-80
47
45
6456
72%
8356
76%
8456
9156
67
64
57%
78%a
90%
5656
92%b
9456
114
60%
7556a
8756
109
6456
. 8956b
9356
0C alving r a t e e q u a ls number o f cows calv ed 7 number i n system .
a ^M eans w ith d i f f e r e n t s u p e r s c r i p t s w i t h i n rows a re s i g n i f i c a n t l y
d i f f e r e n t (P < .0 5 ).
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M''IN U o.
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V562
c o p .2
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Vennes, G. M.
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I S S U E D TO
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