Reproductive Effects of PG600 in Female Pigs

Abstract

PG600 is a synthetic gonadotropin comprising 400 IU equine chorionic gonadotropin (eCG) and 200 IU human chorionic gonadotropin (hCG). Major responsibilities of PG600 were to stimulate follicle growth and induce ovulation. In replacement gilts, a number of large follicles were found after PG600 treatment. Nevertheless, the number of good quality follicles was not different between treatment and control gilts. In primiparous sows, the number of those returning to estrus within 10 days after weaning from PG600 were higher than those in control group. In addition, the administration of PG600 enhanced the number of piglets born alive per litter in the second parity sows. Considering route of administration, subcutaneous injection contributed to the greater number of gilts expressing estrus than intramuscular injection. In addition to dosage effect, it was found that ovulation rate of the pigs treated with 1.0 dose of PG600 was significantly lower than that of those injected with 1.5 and 2.0 doses of PG600. Moreover, treatment with 1.5 dose of PG600 resulted in more number of large follicles than using 0.5 dose (25.7 vs 19.2 follicles, p<0.01). Besides, using 1.5 dose of PG600 contributed to the longest time of estrus (2.7 d, p<0.05), comparing with 0, 0.5, and 1.0 doses of PG600. Nonetheless, treatment with 1.5 dose of PG600 led to a high incidence of follicular cyst formation which restricted the ovulation, contributing to low conception rate.