Estrous Synchronization
by Dr. Ray Favero
Estrous synchronization is drug treatment to induce heat and ovulation in a large
percentage of females at a predictable time. Several methods of estrous synchronization have
been developed for use in cattle. Many of these procedures are not acceptable in whitetail deer.
Many cattle estrous synchronization programs require that females are monitored for heat activity
and artificial insemination is preformed twelve hours after being detected in heat. Effective
estrous synchronization programs in whitetail deer allow for all females to .be inseminated at a
predetermined time. Trying to artificially inseminate some of the females on one day and then
others on the next day would be very stressful on whitetail deer and functional programs of
estrous synchronization have been developed.
The most common treatment for estrous synchronization involves the use of a CIDR. A
CIDR is a silicone device that contains progesterone. Progesterone is a natural hormone that
functions to keep an animal pregnant or out of heat. A CIDR acts to Reep the female out of heat
so that when it is removed, the female will come into heat. An injection of PMSG (pregnant mares
serum gonadotropin) acts to ensure that the female will produce follicles and to improve the
efficiency of the synchronization by improving the synchrony of the resulting ovulations.
Estrous synchronization procedures are the most effective after a female has started
having heat cycles. This is why it is helpful to evaluate fawning dates from natural service to
determine an average'~reeding date. From this.a reasonable artificial insemination date can be
determined.
To start the estrous synchronization procedure a CIDR is inserted into the vagina of the
doe. The CIDR is shaped like the letter T, and the arms of the T are bend forward to place the
CIDR into a the insertion tool. A short plastic string is attached to the base of the T to aid in
removal of the device. The arms of the T are placed in the most forward portion of the does
vagina. A small amount of anti-microbial salve also acts as a lubricant during insertion of the
CIDR. . .
After remaining in the females vagina for 14 to 16 days the CIDR is removed. At the time
of removal, an injection of PMSG (150 to 200 IU) is administered. The artificial insemination
procedure is preformed 56 to 66 hours after the removal of the CIDR and injection of PMSG.
Some producers are having success using vasectomized bucks to detect heat and
preforming artificial insemination about 12 hours after heat is detected. This procedure is very
labor intensive, as heat needs to be checked twice daily. Some producers use paint on the inner
front legs and belly of the bucks. As a female is mounted by the buck, paint is transferred to the
female and this indicates that the female needs to be inseminated. Several producers used this
method on does fav\tns. Does fawns begin having heat cycles at different times during the
season, and therefore it is difficult to determine the best time to start an estrous synchronization
program on these females.