Estrus Synchronization of Replacement Gilts Using Estradiol Cipionate and PGF(2α) and Its Effects on Reproductive Outcomes

SIMPLE SUMMARY: The successful introduction of gilts into breeding groups is a key component of overall productivity. Therefore, the development of estrus synchronization protocols that optimize labor and time would benefit pig production. In this study, we evaluated the effectiveness of the estrus synchronization protocol using a single administration of estradiol cypionate on day 12 of the estrus cycle to mimic the maternal recognition of pregnancy in pigs and thus prolong luteal function. Subsequently we treated gilts which displayed prolonged luteal function with prostaglandin F2 alpha (PGF2α) to induce luteolysis and synchronize estrus. We also evaluated the effect of this protocol on fertility and ovarian function. We observed that a single administration of estradiol cypionate at the time of maternal recognition of pregnancy was effective to induce prolonged luteal function, and treatment of these gilts with PGF2α resulted in fertile estrus within a short period of time. Furthermore, no deleterious effects were observed on fertility, follicular development, uterine histoarchitecture, and ovarian function. Based in our results, a single administration of estradiol cypionate followed by PGF2α injection was effective to synchronize estrus in gilts without deleterious effects of reproductive function. ABSTRACT: In this study, we evaluated the effectiveness of using estrogen-induced prolonged luteal function followed by prostaglandin F2 alpha (PGF2α) treatment to synchronize estrus in gilts. On day12 of the estrus cycle (D0 = first day of standing estrus), 52 gilts were assigned at random to two experimental groups: non-treated gilts (CON, n = 22), serving as controls, and prolonged luteal function group (CYP, n = 30), receiving a single treatment with 10 mg of estradiol cypionate intramuscularly Starting on day 12, blood samples were collected for estradiol and progesterone assays. Estrus detection started on day 17. Gilts from the CON group were inseminated at the onset of natural estrus. On day 28 CYP gilts were treated with PGF2α to induce luteolysis and inseminated at the onset of estrus. Gilts were slaughtered 5 d after the last insemination. A single treatment with estradiol cypionate prolonged luteal function in 90% of treated gilts. The duration of the estrous cycle was longer (p < 0.0001) for CYP gilts compared to CON gilts. CYP gilts showed synchronized estrus 3.96 ± 0.19 d after induction of luteolysis. The conception rate was similar (p = 0.10) for CON and CYP gilts. No difference was observed in the embryo recovery rate (p = 0.18) and total number of embryos per female (p = 0.06). The percentage of unfertilized oocytes, fragmented embryos and viable embryos was similar among females from CON and CYP groups (p > 0.05). The treatment of gilts with a single application of 10 mg of estradiol cypionate on day 12 of the estrous cycle was effective in prolonging luteal function and treatment with PGF2α resulted in synchronized estrus. Additionally, the synchronization protocol had no deleterious effect on fertility and embryonic development.