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

Twenty-two goats were superovulated with PMSG; 84 h after the onset of estr us the goats were treated with saline solution (control group n=7), hCG (hC G 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 cas e the CL were counted and classified according to their appearance as norma l-looking or as regressing. Blood samples for progesterone determination we re collected every 12 h from Day 1 to Day 6. Premature luteal regression wa s considered to have occurred if progesterone concentrations declined to le ss 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 contro l, hCG and GnRH groups, respectively. Progesterone concentrations were high er 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 wets a significan t (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 c ontrol group (2.6 +/- 2.1). The number of large follicles present on the ov aries on Day 6 post estrus had negative correlations with progesterone conc entrations (P=0.05) and with the number of normal-looking CL (P<0.05). It i s concluded that the administration of hCG 84 h after the onset of estrus p revents premature luteal regression in goats superovulated with PMSG. (C) 1 998 by Elsevier Science Inc.