Abstract
This study investigated the effect of three intramuscular injections of Prostaglandin F2α (PGF2α) 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 PGF2α 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 PGF2α injection and estrus detection was conducted daily. Results showed that 100% of Group A came into estrus 96 hours after the second PGF2α 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 PGF2α injection. Control gilts did not express behavioral estrus during this study, suggesting that PGF2α 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 PGF2α 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 PGF2α-synchronized gilts may be quite similar to those of naturally cycling in-estrus gilts.