Abstract
The present study was conducted to evaluate the effect of a pretreatment with insulin on ovarian and fertility response in true anestrous buffaloes with to gonadotrophin-releasing hormone (GnRH). Eighteen buffaloes with inactive ovaries were randomly allocated into three groups: Group-I treated with GnRH (G1, n=6) where each buffalo received an intramuscular injection of 20 mu g of Buseralin acetate (Day 0); Group-II treated with insulin plus GnRH (G2, n=6) in which each buffalo received a subcutaneous injection of long acting bovine insulin at the dose rate of 0.25 IU/kg bodyweight once daily for 3 consecutive days, followed by an intramuscular injection of 20 mu g of Buseralin acetate on Day 4; and the control group (G3, n=6) in which each buffalo given an intramuscular injection of 2.5 ml of sterile saline on Day 0. In response to the treatment, estrus was 33.33% and 66.66% of the animals within 9.5 +/- 3.18 and 26.5 +/- 6.61 days from the start of the treatment, respectively, in G-1 and G-2; however, estrus was induced in none of the control animals. The conception rate at induced estrus was 100% in both the treatment groups. The mean serum progesterone (P-4) concentration was less than 1 ng/ml on day before the start of treatment, day 7, and 14 following the start of treatment in all the experimental animals. After returning to its basal level at induced estrus (i.e. 0.19 +/- 0.04 and 0.32 +/- 0.03 ng/ml) the P-4 concentration increased significantly (i.e. 4.47 +/- 0.58 and 4.27 +/- 0.35 ng/ml) on day 10 post estrus, respectively, in G-1 and G-2 (p<0.05). No significant difference in serum estradiol-17 beta (E-2) concentration was recorded on the day before the start of treatment, day 7 and day 14 following the start of treatment either within or between the treatment groups. The serum E-2 concentration increased significantly at induced estrus, i.e. 47.69 +/- 3.92 and 47.15 +/- 2.93 pg/ml, respectively in G-1 and G-2, and again returned to its basal level, i.e. 13.08 +/- 1.32 and 10.88 +/- 0.99 pg/ml, significantly at day 10 post estrus, respectively in both the treatment groups (P<0.05). It is concluded that pretreatment with insulin for 3 days before GnRH injection increases estrous induction rate and enhances ovarian and fertility response in true anestrous buffaloes.