A comparison of fertility with a Cosynch protocol versus a modified Ovsynch protocol which included estradiol in lactating dairy cows during the summer season in Jordan
Anim Reprod, vol.8, n1/2, p.32-39, 2011
A total of 332 postpartum (pp) lactating Friesian cows allocated in two treatment groups at a commercial dairy farm were used to study the effect of a modified Ovsynch protocol supplemented with exogenous estradiol (E2) on fertility in lactating dairy cows during the summer season. All cows were injected with gonadotrophin releasing hormone (GnRH), followed 7 days later by an injection of prostaglandin (PGF2α). Then cows were randomly assigned to receive GnRH and TAI 72 h after PGF2α (CO-72; control group) or E2, GnRH and TAI at 48, 56 and 72 h, respectively after PGF2α (OV-56+E2). Estrus response for cows in the OV-56+E2 (59.8%) group was higher (P < 0.05) than for cows in the CO-72 (40.2%) group. Pregnancy per insemination (P/AI) at two diagnoses (days 30 to 35 and confirmed at days 45 to 50 after AI) were similar between the two treatment groups, but were higher (P < 0.05) for cows that showed estrus (59.8 and 41.2%, respectively) than for cows that did not show estrus (45.5 and 7.9%, respectively). Moreover, P/AI at the two diagnoses were higher (P < 0.05) for cows with a body condition score (BCS) >2.5 (60.1 and 36.4%, respectively) compared to those with BCS <2.5 (44.3 and 16.5%, respectively). Pregnancy losses were higher (P < 0.05) for cows that did not show estrus (82.6%) or with BCS <2.5 (62.8%) than for cows that showed estrus (31.0%) or with a BCS >2.5 (39.5%). No differences were observed in P/AI or pregnancy losses between primiparous and multiparous cows. Results indicate that the OV-56+E2 synchronization protocol resulted in a higher expression of estrus than the CO-72 without improving fertility as measured by P/AI and pregnancy losses. However, cows with high BCS had higher estrus expression, pregnancy rates, and lower pregnancy losses than cows with low BCS during the summer season.
Cosynch, dairy cows, estradiol, fertility, Ovsynch