Optimizing estrus synchronization in tropical hair sheep: ovarian responses and corpus luteum function following prostaglandin or progesterone-based treatments.

Abstract

This study evaluated the ovarian responses and corpus luteum (CL) functionality in Barbados Blackbelly × White Virgin Island crossbred hair sheep subjected to two estrous synchronization protocols in a tropical grazing environment. A total of 40 non-lactating ewes, between 2 and 4 years of age, were randomly assigned to one of two treatment groups. The CIDR + PG group (n = 20) received a 7-day intravaginal CIDR device containing 0.3 g of progesterone, followed by an intramuscular injection of 10 mg dinoprost (PG analogue) upon removal of the device. Conversely, the double PG group (n = 20) received two intramuscular injections of 10 mg dinoprost, spaced 10 days apart. Ovarian structures were monitored via transrectal ultrasonography over a 21-day period, and blood samples were collected periodically to determine plasma progesterone levels. The proportion of ewes that ovulated was comparable between groups: 80% (16/20) in CIDR + PG and 90% (18/20) in the double PG group. The average interval from treatment to ovulation, inter-ovulatory interval, and preovulatory follicle size did not differ between the groups. Notably, the CL area was significantly larger in the CIDR + PG group (p = 0.002), while progesterone concentrations from day 7 to day 13 were higher in the double PG group (p < 0.05). Additionally, CIDR + PG-treated ewes underwent earlier luteolysis, resulting in lower progesterone concentrations during the critical phase for establishing pregnancy. In conclusion, both synchronization protocols effectively induced ovulation; however, the CIDR + PG protocol led to earlier CL regression, which may compromise progesterone support during early gestation and negatively impact reproductive performance in tropical hair sheep.