Synchronization
2 wave cycle
False
Estrus
Metestrus
1
Diestrus
5
10
Proestrus
15
Day of cycle
Estrus
20
22
Progesterone
Wave 2 Ovulates
Wave 1
Follicle decreases
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Day of Cycle
GnRH causes the pituitary gland to secrete both LH and FSH. These two
naturally occurring hormones, in concert with other changing levels of
hormones, cause the ovulation of the dominate follicle present on the ovary.
GnRH can be used to treat cows with cystic ovarian disease or cystic ovaries and
also is used in some estrous synchronization programs. Injections of GnRH help
to synchronize the follicular waves that result in better control over the timing of
ovulation.
PFG is secreted by the uterus and regulates the lifespan of the corpus luteum
(CL). It moves from the uterus directly to the ovaries without circulating in the
venous blood through the heart and back out to the ovaries through the arterial
blood. As PFG causes the regression of the CL, it also causes a decrease in the
progesterone levels as progesterone is secreted by the active CL. PFG is used in
the treatment of uterine infections, to cause abortions up to 100 days after
breeding, expulsion of mummified fetus and for timing of breeding. Keep in
mind that there must be a CL present on one of the ovaries in order for PFG to
work. For instance, when a CL is present at the time PFG is given, the cow will
usually come into heat within 2-5 days. If the PFG is given early in the estrous
cycle before a CL is formed and functional, no induced heat will occur.
Ovulation
GnRH day 1
Luteinization
and resets
follicular
waves
Or causes
ovulation of
larger
follicles
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 0
Day of Cycle
PGF day 7
Follicular
wave
Progesterone
0 1 2 3 4 5 6
7
8
9
Day of Synchronization
10
GnRH
PGF
GnRH
Day 9
Breed
16 Hours
after GnRH
day 7
day 1
0 1 2 3 4 5 6
7
8
9
Day of Synchronization
10
A Happy End !!