EFICIÊNCIA DO CIPIONATO DE ESTRADIOL E DO BENZOATO DE ESTRADIOL EM PROTOCOLOS DE INDUÇÃO DA OVULAÇÃO SOBRE A DINÂMICA OVARIANA E TAXA DE CONCEPÇÃO DE FÊMEAS NELORE INSEMINADAS EM DIFERENTES MOMENTOS.

We aim to evaluate the ovarian dynamics and conception rates of Nelore females subjected to TAI using benzoate or estradiol cypionate as ovulation inducers and inseminated that morning or afternoon. For this, 296 animals received an intravaginal progesterone device and 2,0 mg of estradiol benzoate applied on a random stage of the oestrous cycle, named D0. On D8, the devices were removed and 500 µg of Cloprostenol and 300 IU of equine chorionic gonadotropin were administered. At that time, half of the animals received 1,0 mg of estradiol cypionate, and the other half received 1,0 mg of estradiol benzoate on the following day (D9), establishing the EC and EB treatments respectively. On experiment 1, 38 animals (19 for each treatment) had the ovarian dynamics accompanied by ultrasonography. On experiment 2, 258 animals were randomly distributed according to treatments (EC and EB) in order for the inseminations to occur in the morning (M) or in the afternoon (T) of D10, establishing thus groups EC-M (n = 65), EB-M (n = 65), EC-T (n = 63) and EB-T (n = 65). No difference was found between the treatments for the variables: diameter of ovulatory follicle, time of ovulation, ovulation rate and diameter of corpus luteum, however, the animals treated with estradiol cypionate presented a greater follicular growth rate (EC:0,48 mm/day; EB: 0,29 mm/day). On experiment 2, there was no difference in the conception rate between the groups EC-M (52,3%), EB-M (41,5%), EC-T (41,3%) and EB-T (49,2%).The employment of the estradiol cypionate in substitution to the estradiol benzoate provided a reduction in animal manipulation without compromising the conception rates. Additionally, the extension of the insemination interval seems to be an alternative for the management models using this technology. [ABSTRACT FROM AUTHOR]