MGA¨-PGF
A low-cost system for estrous synchronization
uses melengestrol acetate (MGA) and PGF. MGA is a progesterone-like
feed additive that suppresses estrous as long as females consume
MGA daily. In this estrous synchronization procedure, MGA
is fed at .5 mg./head/day for 14 days. Feeding MGA for 14
days allows cyclic cows to proceed to day 18-19 of their cycle
on their own, but holds them at that stage until the MGA is
removed from their feed. A
majority of cows will exhibit estrous two to five days after
withdrawal of the MGA. This is a subfertile heat and females
should not be bred. These females will ovulate an aged (and
generally less fertile) egg and form a new CL. A single injection
of PGF administered 17 days after the last day of MGA feeding
will regress the CL of the next estrous cycle. Recent reports
from two universities have shown that a PGF injection on day
33 vs. day 31 following MGA withdrawal will increase the number
of animals showing heat within a short period of time. Most
females will show estrous 48 to 72 hours after this PGF injection
and should be inseminated 8-10 hours after detected estrus.
Mass mating all females or those that have not yet displayed
heat at 72 hours (heifers) or 80 hours (cows) after the PGF
injection. This protocol has proven itself time and again
to be the best available for heifers if producers are able
to get heifers to consume the MGA.
Desired
Calving Date:
Instructions Preplanning
1. Enter desired calving date.
Feeding
Program
3. Feed MGA for 14 days
Injection
Program
4. Inject PGF injection
5. Check Heat & Breed for 5 days
