Superovulatory response to gonadotrophin FSH/LH treatment and effect of progestin supplement to recipients on survival of transferred vitrified embryos in goats.

Two experiments were carried out in goats to evaluate the effects of the FSH/LH ratio during treatment on ovarian response and embryo production (experiment 1) and the efficiency of progestin supplementation on pregnancy and the survival of vitrified embryos (experiment 2). In experiment 1, 30 goats were synchronized and allocated to 2 groups (n = 15) corresponding to the following superovulatory treatments with p-FSH (250 IU, over 3 days) having different doses of purified FSH and LH: (group A) control, FSH/LH ratio of 1, kept constant during treatment; (group B) FSH/LH ratio of 2 and daily FSH/LH ratio of 5.0:1.0:0.3 for the first, second, and third days of treatment, respectively. Ovarian response and embryo production were assessed 7.5 days after estrus. In experiment 2, 46 vitrified blastocysts from p-FSH-superovulated donors were transferred to 26 recipients (2 blastocysts per goat) 7.5 days after estrus. The recipients were synchronized with donors and allocated to 2 experimental groups (n = 13). Group C received progestin supplement as fluorgestone acetate (FGA) inserted into the vagina at the time of embryo transfer, replaced with a new one 16 days later, and maintained until the 45th day of pregnancy; group D, no treatment (control). Pregnancy was diagnosed by transrectal ultrasound scanning on Days 30 and 45 after estrus and followed to term. The results indicated that the increase in FSH/LH ratio from 1 to 2 with decreasing daily FSH/LH (treatment B) did not improve the superovulatory response. Superovulatory treatment A (control) advanced (P < 0.05) the onset of estrus and showed a higher ovulation rate compared to group B (14.9 vs. 10.9; P < 0.05). Fertilization rate, embryo yield, and mean number of transferable embryos in group A (7.5) were higher (P < 0.05) than those in group B (3.2). Recipient goats receiving progestin supplementation (group C) showed a higher (P < 0.05) pregnancy rate and embryo survival (kids born per embryos transferred; 69.3% and 73.1%) than the controls (group D; 23.3% and 19.2%). In conclusion, regimen A with FSH/LH ratio of 1 kept constant during the treatment gave the best ovarian response and embryo production. The progestin supplementation as FGA-pessary administered at embryo transfer time to the 45th day of pregnancy improved the pregnancy rate, kidding rate, and embryo survival of transferred vitrified embryos. Intravaginal progestin supplement has the potential to reduce the incidence of pregnancy losses during early pregnancy.