Estrus Responses and Hormonal Profiles of Gilts Following Treatments with Prostaglandin F_2α

This study investigated the effect of three intramuscular injections of Prostaglandin F_2α (PGF_2α) administered seven days apart on estrus responses and some reproductive hormonal profiles in post-pubertal gilts.Sixteen gilts were divided into groups A, B, C, and D, with four animals in each group. Group A, B and C gilts were treated with PGF_2α injections intramuscularly at doses 5mg,7.5mg and 10mg per gilt respectively on Days 0, 6 and 13 of the experiment. Group D (Control) were treated with intramuscular injections of 2ml phosphate-buffered saline (PBS) instead. Serum samples were collected every 24 hours for four days after each PGF_2α injection and estrus detection was conducted daily. Results showed that 100% of Group A came into estrus 96 hours after the second PGF_2α injection,while 50% of Group B came into estrus after the first injection; with the other 50% exhibiting estrus following the 2nd injection. Only 50% of Group C displayed estrus signs and this was observed following the second PGF_2α injection. Control gilts did not express behavioral estrus during this study, suggesting that PGF_2α may have induced estrus in the treated animals. LH and estradiol concentrations were significantly different in Group A and B when compared to the control following the 2nd PGF_2α injection. In all, it was observed that serum concentrations of LH, FSH and oestradiol-17β reached maximal levels just prior to expression of estrus, thus suggesting that the pattern of reproductive hormonal changes in PGF_2α-synchronized gilts may be quite similar to those of naturally cycling in-estrus gilts.