Effect of timing of insemination after CIDR removal with or without GnRH on pregnancy rates in Nili-Ravi buffalo.

There are limited studies available on when to inseminate, if using CIDR or CIDR-GnRH protocols for optimal fertility in buffalo. Therefore, the objective of the present study was to determine the optimum time of AI in relation to CIDR removal with or without GnRH in buffalo. All buffalo (n=201) received CIDR on Day 0, PGF2α on Day 6 and CIDR were removed on Day 7. In 50 of these buffalo GnRH was administered 36 h after CIDR removal. Furthermore, CIDR (n=151) and CIDR-GnRH (n=50) were randomly divided to receive timed artificial insemination (TAI), either at 48, 60 or 72 h after CIDR removal. Ultrasonography was performed for follicular development and for pregnancy diagnosis. The results revealed that, mean interval to ovulation was shorter (P<0.05) in buffalo receiving CIDR-GnRH than CIDR (68.40 ± 1.73 compared with 76.13 ± 1.66 h, respectively). The pregnancy rates were higher (P<0.05) in buffalo inseminated either at 48 (50%) or 60 (59%) than at 72 h (18%) in CIDR-GnRH protocol; whereas, in CIDR buffalo pregnancy rates were higher (P<0.05), at 60 (37%) or 72 (40%) than at 48 h (10%). In conclusion, the optimal time of AI is between 48-60 h in CIDR-GnRH and between 60-72 h in CIDR protocol for enhancing fertility in buffalo.