Effects of Prostaglandin F2α on Estrous Cycle or Corpus Luteum in Mares and Gilts

In Experiment 1, 20 pony mares were assigned by randomization to seven groups and six of the groups were injected subcutaneously (SC) with 1.25 mg prostaglandin F2α(PGF2α) on one of the following days of the estrous cycle (number of mares): 1(3), 4(3), 7(3), 10(3) or 13(2) post-ovulation or on day 2 of estrus (3). In Experiment 2, 24 pony mares were assigned by randomization to eight groups (three mares each) which were given an intramuscular (IM) or SC injection of one of the following doses of PFG2α; on day 7 post-ovulation: 0(controls), .25, .75 or 1.25 milligrams. In Experiment 3, three groups of three gilts each were injected IM on day 12 of the estrous cycle with one of the following doses of PGF2α: 0, 10 or 20 milligrams. In Experiment 1, both estrus and ovulation appeared to be synchronized (mean intervals from treatment to estrus and ovulation were not significantly different) among mares given 1.25 mg PGF2α SC on days 7, 10 or 13 post-ovulation, but not among mares given PGF2α on days 1 or 4 post-ovulation or day 2 of estrus.