Effect of insulin administration on ovarian function and estrus induction in acyclic goats

The present experiment was conducted to study the effect of insulin on follicular development, ovarian steroid profiles and estrus induction in 14 non-descript acyclic goats. Experimental animals were randomly divided into two groups, i.e. group A (control, n = 7) and group B (insulin-treated, n = 7). The animals of treatment group were injected with long acting bovine insulin subcutaneously at 0.2 IU/kg body weight once daily for five consecutive days. However animals of control group were injected with normal saline only as a placebo. Animals were subjected to detection of estrus twice daily (morning and evening) using an apronized buck and visual observation of estrus signs. Simultaneously animals of both groups were subjected to B-mode transrectal ovarian ultrasonsography for follicular development and blood collection on days 0, 4, 8, 12, 16, 20, 24 and 28 for the estimation of serum estradiol-17β, progesterone and nitric oxide (NO) profiles, respectively. The results revealed significantly greater total number of follicles in insulin-treated goats as compared to control. The diameter of corpus luteum (CL) in insulin-administered goat was ranging between 5.14 and 6.14 mm. Significantly higher concentrations of estradiol-17β on days 4 and 8 and progesterone on days 12, 16, 20 and 24 were observed in insulin-treated goats as compared to control. Significantly higher concentration of NO was observed in insulin-treated group as compared to control. In the treatment group estrus was recorded in 5/7 goats (71%), with estrus duration of 19 ± 2.6 h at a mean interval of 189 ± 17.7 h from the initiation of treatment. Ovulation occurred in 4/5 (80%) of responding animals, as confirmed by detecting CL ultrasonographically. However in control none of the animal displayed signs of estrus during the observation period. The results indicate favorable effect of insulin on ovarian function.