Abstract

USLENGHI, G; CABODEVILA, J  and  CALLEJAS, S.S.. Effect of estradiol cypionate and GnRH on synchronization of ovulation and pregnancy rate at FTAI in non-suckled cows. InVet [online]. 2016, vol.18, n.2, pp.301-306. ISSN 1668-3498.

Two experiments were conducted to evaluate the effect of estradiol cypionate (ECP), Gonadotropin realizing hormone (GnRH) and the combination of both on synchronization of ovulations and pregnancy rate at fixed-timed artificial insemination (FTAI). In Experiment 1, forty cows were randomly assigned to received different ovulation inducers (n=10/group): 1 mg of ECP; 1 mg of estradiol benzoate (EB); 10.5 μg of buserelin acetate (GnRH); 1 mg of ECP plus 10.5 μg of GnRH. Ovarian ultrasonography examinations were performed every 12 h from intravaginal device removal to ovulation, to detect the dominant follicle and ovulation. In Experiment 2, cows received the same treatments: Group ECP: n=71; Group EB: n=70; Group GnRH: n=67; Group ECP-GnRH: n=70, and FTAI 48-50 h after intravaginal device removal. Pregnancy rate was determined on day 35 by ultrasonography. Variables were analyzed by SAS. There was no effect of treatments on follicular dynamics, and on the mean interval to ovulation (P>0.05); however, GnRH treated cows had scattered distribution of ovulations (P<0.05). Pregnancy rate did not differ (P>0.05) between treatments (P>0.05; ECP: 46.3%, EB: 54.3%, GnRH: 47.9% y ECP+GnRH: 60.0%). In conclusion, GnRH administration in cows that receive ECP at PID removal tended to improve the distribution of ovulations, but did not enhance pregnancy rate at FTAI.

Keywords : Estradiol; Buserelin acetate; Artificial insemination; Ovulation; Pregnancy rate.