Synchronization and resynchronization strategies to improve fertility in dairy buffaloes

Dairy buffalo has an integral role in the sustenance of economics due to its substantial contribution in milk and meat industry, however, the reproduction in this species is challenging. During the last decade, our laboratory conducted a series of experiments to encapsulate the solutions of the problems through optimizing pre- and post-insemination interventions in dairy buffaloes. In an unique study, we proposed that timing of ovulation with reference to the onset of standing heat during spontaneous estrus is delayed, and subsequently re-framed the traditional AM-PM rule (AI after 12 h of standing heat) to AM-AM or PM-PM (AI after 24 h of standing heat) to achieve the optimum fertility using frozen thawed semen in dairy buffaloes. Pregnancy per AI (P/AI) varied substantially either via injecting single shot of prostaglandin (PG) F_2α to perform AI at detected estrus or applying standard ovsynch protocol for timed AI (TAI) in buffaloes. However, estrus response, and P/AI remained similar either with used or new controlled internal drug release device in dairy buffaloes. Additionally, the incorporation of estradiol benzoate in progesterone (P4) based protocol resulted in controlled emergence of follicular wave and increased the estrus intensity in buffaloes. Thereafter, we fine-tuned P4-based protocols to optimize the ovulation window for TAI either using GnRH or human chorionic gonadotropin (hCG) or equine chorionic gonadotropin that ultimately improved the fertility in dairy buffaloes. Although, these hormonal interventions resulted in decent fertility, yet it was consistently being compromised due to early or late embryonic losses in dairy buffaloes. Administration of hCG or GnRH on d 7 or 23 or 25 post AI has been proved beneficial to enhance the embryonic survival in buffaloes. Recently, resynchronization program as an aggressive reproductive management approach has been tested that served as a dual-purpose tool to increase overall herd fertility and reduce embryonic losses at commercial buffalo farm operations. Taken together, we concluded that the solutions to the problems of reproductive function are now clearly available with acceptable fertility, however, their application to the small holder buffalo farming remains challenging.