Repeated administration of hCG on follicular and luteal characteristics and serum progesterone concentrations in eCG-superovulated does

The objective of this study was to evaluate the effect of repeated administration of hCG on the follicular and luteal charactristics and serum progesterone concentrations in eCGsuperovulated Merghoz does. The estrous cycles of 40 adult does were synchronized following a 12-day treatment with intravaginal sponges (Chronogest®), with 1000 IU eCG injected 2 days prior to sponge removal. On the day of sponge removal (day 0), the females were randomly assigned to 4 treatments. The first group (h1; n = 10), received an i.m. hCG injection (500 IU; Pregnyl®) on the day 0. The second group (h2; n = 10), received an i.m. hCG (500 IU) injection on days 0 and 1, while the third group (h3; n = 10) received i.m. hCG (500 IU) on days 0–2. Does in the control group (n = 10) did not receive any hCG treatment. Blood samples were taken on days 0, 1, 2, 5 and 8 and analysed for serum progesterone (P4) concentrations. Premature luteal regression was considered to have occurred if the P4 concentrations declined to less than 1 ng/mL by day 8 following sponge removal. On day 8 goats were slaughtered and ovaries recovered for evaluation. In each case the CL’s were counted and classified according to their appearance – as normal or as regressing. According to the serum P4 concentration on day 8, 42.8% (3/7), 0% (0/8), 0% (0/7) and 0% (0/6) of the goats underwent premature luteal regression in the control, h1, h2 and h3 groups, respectively. The control group was the only group in which there was a significant increase in the number of regressing CL’s on day 8 (5.1±1.5; P < 0.05). The characteristics of the CL’s, including the mean diameter and weight was greater (P < 0.05) in the h2 and h3 groups, compared to the control group (10.9±0.7, 11.0±0.9 vs. 7.9±1.1mm and 640.0±101.4, 691.7±111.7 vs. 294.3±143.7 mg, respectively). No differences (P < 0.05) in the number of large follicles present on the ovaries were recorded on day 8 between the groups. However, the diameter of the large follicles present on the ovaries on day 8 was greater (P < 0.05) in goats in the h2 and the h3 groups, compared to the control (15.3±0.6 and 12.9±0.3 vs. 8.6±1.7mm, respectively; P < 0.05). The serum P4 concentrations were higher in the h2 and the h3 groups than in the control group on days 2 and 8. The serum P4 concentrations on day 8 also recorded a positive correlation with the normal CL’s, CL diameter and CL weight (P < 0.001). These results indicate that the repeated administration of hCG post-sponge removal presumably prevents premature luteal regression and improves luteal function in goats after eCG-superovulatory treatment. However, neither the number of persistent follicles nor the diameter of the persistent follicles was reduced.