5d CIDR-Heatsynch improves the circulatory estradiol levels, estrus expression and conception rate in anestrus buffalo ( Bubalus bubalis ).

The present study aimed to investigate whether increasing estradiol (E 2 ) during preovulatory period would increase estrous expression, luteal profiles and conception rate in 5d CIDR based timed AI protocol. A total 156 anestrus buffalo allocated (78 per group) to either 5d CIDR-Cosynch (d-5: CIDR + GnRH; d0: PGF 2α +CIDR removal; 72 h post-CIDR removal: GnRH) or 5d CIDR-Heatsynch (d-5: CIDR + GnRH; d0: PGF 2α +CIDR removal; 24 h post-CIDR removal: estradiol benzoate) group. All the buffaloes inseminated at 72 and 84 h post-CIDR removal. A subset of buffalo ( n  = 58) were subjected to examination of the follicle diameter and luteal profile during protocol, post-AI on days 5 and 12. The buffalo in 5d CIDR-Heatsynch had greater ( p  < .05) E 2 concentrations, estrus induction and increasing trend ( p  < .08) for conception rate (57.7% vs. 43.6%) than 5d CIDR-Cosynch. The percentage of pregnant buffalo that exhibited estrus signs was greater ( p  < .01) in 5d CIDR-Heatsynch than 5d CIDR-Cosynch. Positive correlation ( p  < .01) was observed between POF and E 2 concentrations; POF and CL diameter, CL diameter and P 4 concentrations. Estrus response and P 4 concentrations were indicators of probability of pregnancy. In conclusion, 5d CIDR-Heatsynch tended to improve conception rate. The estrus expression and P 4 concentrations (d5 and 12 post-first-AI) is the indicator of probability of pregnancy in buffalo.