Efficacy of the Ovsynch protocol for synchronization of ovulation and fixed-time artificial insemination in Murrah buffaloes ( Bubalus bubalis)

Abstract

Two experiments were conducted to assess the timing and synchrony of ovulation, plasma LH concentrations, and pregnancy rate in Murrah buffaloes ( Bubalus bubalis) treated with the Ovsynch (GnRH-PGF 2α-GnRH) protocol. In Experiment 1, 10 non-lactating cycling buffaloes received 10 μg of a GnRH analogue i.m. (buserelin acetate) without regard to the stage of the estrous cycle (day of treatment, day 0), followed by 25 mg of PGF 2α i.m. (dinoprost thromethamine) 7 days later. A second-treatment of the same GnRH analogue (10 μg, i.m.) was given 48 h after PGF 2α. Ovulation was confirmed by transrectal palpation (at 2-h intervals) from the second-GnRH treatment to detection of ovulation or up to 96 h after the second-GnRH treatment. Plasma LH concentrations were determined in blood samples collected at 15-min intervals for 6 h, starting at the second-GnRH treatment, and thereafter at 2-h intervals until 2 h after detection of ovulation. Ovulation occurred in 9/10 buffalo (90%) 23.3 ± 1.3 h (mean ± S.E.M.; range 20–32 h) after the second-GnRH treatment. Peak LH concentrations 13.5 ± 3.5 ng/mL (range 3.9–40.0 ng/mL) occurred 2.1 ± 0.1 h (range 1.2–3.0 h) after the second-GnRH treatment. In Experiment 2, 15 lactating, cycling buffaloes were subjected to the Ovsynch protocol, with fixed-time AI 12 and 24 h after the second-GnRH treatment and 75 lactating buffaloes were inseminated, approximately 12 h after detection of spontaneous estrus. Pregnancy rates were 33.3% for TAI and were 30.7% for buffaloes inseminated following spontaneous estrus ( P = 0.84). In conclusion, the Ovsynch protocol effectively synchronized ovulation in Murrah buffaloes and resulted in conception rates (to two fixed-time inseminations) that were comparable to those achieved with a single AI after detection of spontaneous estrus.