Efficiency of Ovsynch and CIDR protocols for estrus synchronization was determined by conception rate in Nili Ravi buffaloes in low and peak breeding seasons under farm condition. The protocol with better conception rate (%) was then tested under field condition in the respective season. Ovsynch protocol comprised of administration of GnRH analogue (Lecirelin, d 0) PGF2α analogue (Cloprostenol, d 7) and Lecirelin (d 9). Animals were inseminated at 12 and 24 hours after last Lecirelin injection using chilled semen. In CIDR protocol, the device (containing 1.38 g progesterone) was used for 8 days and Cloprostenol was administered on day 7. Animals were inseminated twice at 48 hours and 60 hours after CIDR removal using chilled semen. Conception rate was higher (P=0.07) in CIDR group (30.0%) than that in Ovsynch group (0.0%) under farm condition in low breeding season, however this difference was statistically non significant. Conception rate did not differ (P=0.47) between Ovsynch (70.0%) and CIDR (54.5%) groups under farm condition in peak breeding season. In field trial, a conception rate of 36.8% was achieved with CIDR in low breeding season and a conception rate of 54.2% was achieved with Ovsynch in peak breeding season (P=0.26). In conclusion, CIDR as compared with Ovsynch protocol seemed to be more effective for estrus synchronization during low breeding season in Nili Ravi buffalo. Ovsynch and CIDR were equally effective for estrus synchronization during peak breeding season.

Key words: Breeding seasons, Buffaloes, CIDR, Conception rate, Ovsynch, TAI