Premature luteal regression in goats superovulated with pmsg: Effect of hCG OR GnRH administration during the early luteal phase

Abstract

Twenty-two goats were superovulated with PMSG; 84 h after the onset of estrus the goats were treated with saline solution (control group n=7), hCG (hCG group, n=7), or GnRH (GnRH group, n=8). The ovaries of all the goats were laparoscopically examined 3 and 6 d after the onset of estrus. In each case the CL were counted and classified according to their appearance as normal-looking or as regressing. Blood samples for progesterone determination were collected every 12 h from Day 1 to Day 6. Premature luteal regression was considered to have occurred if progesterone concentrations declined to less than 1 ng/mL by Day 6. According to progesterone concentrations, 57.5, 0 and 37.5% of the goats underwent premature luteal regression in the control, hCG and GnRH groups, respectively. Progesterone concentrations were higher in the hCG group than in the other groups on Days 5 and 6 post estrus (P<0.05). The control group was the only one in which there was a significant (P<0.05) increase in the number of regressing CL between Day 3 (1.6 ± 1.4) and Day 6 (7.3 ± 1.4). It was also the only group in which there was a significant decrease in the number of normal-looking CL between Day 3 (12.6 ± 2.1) and Day 6 (2.6 ± 2.1). On Day 6 the animals treated with hCG had significantly more normal-looking CL (12.0 ± 2.3) than those in the control group (2.6 ± 2.1). The number of large follicles present on the ovaries on Day 6 post estrus had negative correlations with progesterone concentrations (P=0.05) and with the number of normal-looking CL (P<0.05). It is concluded that the administration of hCG 84 h after the onset of estrus prevents premature luteal regression in goats superovulated with PMSG.