Desenvolvimento folicular e ovulação de fêmeas Nelore (Bos taurus indicus) sincronizadas

Abstract

This work was developed to contrast the follicular development in Nellore heifers and cows submited to ovulation synchronyzation with norgestomet (NOR) and estradiol benzoate (BE). Five females of each category were submitted to the following protocol: NOR implant in the ear with 2.0 mg of BE on day zero (D0), removal of implant on D8, followed by the application of 0.5 mg of cloprostenol. On D9 all the animals received a second dose of 1.0 mg of BE. Ultrasound evaluations were daily performed from D0 to D8; every 12 hours from D8 to D9 and every six hours of D9 until ovulation. The average diameter of the ovulatory follicle was 8.02±0.39 mm for heifers and 9.10±0.24 mm for cows, with difference between two categories (p<0.05). The average interval between beginning of the protocol and the appearance of a new follicular wave was 3.80±0.37 days for heifers and 3.50±0.50 days for cows. The ovulation occurred, on average, 40.6±1.47 hours for heifers and 41.50±3.77 for cows after the second dose of BE. For these intervals didn't have difference between two categories (p>0.05). According these results we can conclude that the follicular development of Nellore heifers and cows submited to ovulation synchronyzation with NOR and BE occur of similar way, with the ovulatory follicle bigger in the cows.