Abstract
The present study was conducted to evaluate the effect of exogenous insulin alone and in combination with GnRH on estrous induction and fertility response in true anestrous buffalos. Forty buffaloes with inactive ovaries were randomly allocated into Four groups: Group-I (G1, n=10) treated with long acting bovine insulin at the dose rate of 0.25 IU/ kg bodyweight subcutaneous once daily for 5 consecutive days, Group-II (G2, n=10) treated with GnRH where each buffalo received an intramuscular injection of 20 μg of Buseralin acetate (Day 0); Group-III treated with insulin plus GnRH (G3, n=10) 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 μg of Buseralin acetate on Day 4 ; and the control group (G IV, n=10) in which each buffalo given an intramuscular injection of 2.5 ml of sterile saline on Day 0. In response to the treatment induction of estrus in higher number of animals using insulin in combination of GnRH (G-3, 60%) as compared to insulin alone (G1, 50.00%) and GnRH alone (G2, 40%), however no animal induced in estrus in control group (G4, 0.0%). The onset of estrus interval (days) following start of treatment was shorter in G-2 (9.53.18), as compared to G-3 (15.5  4.61) and G-1 (250.94) respectively. The ovulation rate at induced estrus was 100% in all the treatment groups. All the animals bred at induced estrus with the 100% conception i.e. in G-1, G-2 and G-3, respectively.

Key words: Insulin, True anestrous, Buffaloes, GnRH, Fertility