Abstract   

    Pluriparous Nili-Ravi buffaloes (n = 18) which calved during the months of November to July were treated with a single injection of 50 mg of GnRH on day 30 postpartum followed by an injection of 150 mg of PGF2a seven days later. Response of hormonal treatment in terms of induced estrus within 96 hours after the injection of PGF2a was 27.8%. Only 3 buffaloes conceived at the induced estrus giving an overall fertility response of 16.7%. During first three months postpartum, 61.1% of buffaloes resumed observable estrous activity with a mean postpartum interval of 53.71+15.6 days. Ten of eighteen buffaloes (55.5%) became pregnant within 90 days postpartum with an average postpartum interval of 63.01+20.0 days. Retrospective grouping of experimental buffaloes that received hormonal treatment during initial stage (n=9) or terminal stage (n=9) of the low breeding season revealed that the estrus response (within 96 hours) was higher during initial than the terminal stage (44.4 vs 11.1%; P<0.05). Cumulative estrous activity during first 90 days postpartum was also higher during the initial stage (77.7 vs 44.4%; P<0.05). The mean postpartum intervals to first observed estrus (47 .3 vs 64.5 days) and to conception (56.8 vs 72.5 days) were significantly shorter during the initial than the terminal stage of low breeding season. It is concluded that during the low breeding season, the early postpartum Nili-Ravi buffaloes show poor response to exogenous GnRH plus PGF2a treatment, in terms of induced estrus and subsequent fertility. The efficiency of hormonal treatment is, however, comparatively better during the initial than the terminal stage of low breeding season.    

Key words: Buffalo, GnRH, PGF2a, Low breeding season, Postpartum, Reproduction.