Ultrasound and endocrine evaluation of the ovarian response to a single dose of eCG folllowing a 14-day treatment with CIDR in the breeding season in goats

The objective of the present study was to compare the effect of different dosage of equine chorionic gonadotrophin (eCG) on the follicular dynamics and hormonal concentrations in Alpine goats, which were subjected to estrous and ovulation synchronization protocols with controlled internal drug released (CIDR) devices containing 0.3 g of progesterone for 14 days during breeding season. Female goats (n = 24) were divided at random into four groups of 6 animals each. On the day of the dispositive removal, the animals received 0 (T1-Control), 200 (T2), 300 (T3) and 400 UI of eCG (T4). Follicular development was observed ultrasonographically starting 1 day prior to eCG administration until the next ovulation. The daily plasma E-2 and P-4 concentrations were determined using RIA. The continuous variables were evaluated with the variance analyses under GLM procedures of SAS statistical package. The mean comparison was carried out with the Tukey-Kramer test. Estrous response for all treatment groups was 100%. Estrous cycles with three and four waves of follicular growth were observed. The size of the largest follicle was smaller (P<0.01) in control animals of wave 3 (5.5x0.50 mm) when compared with the Treatment 3 at the same wave (7.17x0.35 mm). The effects of eCG on follicular growth showed a significant increase in the number of small and medium follicles (P<0.05) than for the control group. The mean number of corpora lutea were higher (P<0.05) in T4 (400 UI) than T2 (200 UI), showing 4.27x0.23 vs 1.95x0.19 CL, respectively. There were significant differences in plasma concentrations P-4 (P<000.01) and E-2 (P<0.001) among treatments. The use of CIDR plus intramuscular injection of eCG was effective in inducing estrus, increasing the recruitment of small follicles and accelerating the mechanism of follicular growth in Alpine goats.