Periódicos Brasileiros em Medicina Veterinária e Zootecnia

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Eficiência reprodutiva de vacas primíparas da raça Nelore

Oliveira, Vanessa Soares AraújoBonato, Gabriela LuciaSantos, Ricarda Maria dos

Background: Reproductive efficiency is one of the most important characteristics for beef cattle. Bos indicus cattle have longer periods of postpartum anestrus, which contributes to poorer reproductive efficiency of zebu cows when compared with that of Bos taurus , this facts are particular relevant in primiparous cows. These challenges are more important in primiparous cows in pasture management systems because the intake of nutrients during the postpartum period is not sufficient to meet requirements for growth as well as lactation. The objectives of this study were to evaluate the days postpartum at conception and the pregnancy rate at the end of a 90 days breeding season in primiparous and multiparous cows. Materials, Methods & Results: The study was conducted at the Experimental Farm of the Capim Branco, Federal University of Uberlandia, in the breeding season of 2009/2010. It was used 14 primiparous and 84 multiparous Nelore cows. The females were treated with the following protocol. On Day 0, all cows received an intravaginal device containing 1.9 g progesterone (CIDR®) and 1.0 mg, i.m. of estradiol cypionate (ECP ®). On Day 7 the cows received 12.5 mg, i.m. dinoprost tromethamine (Lutalyse®). On Day 9, the intravaginal devices were removed, and calves were temporally weaned. On Day 11 (48 h after intravaginal device withdrawal), all cows were inseminated and calves reunited with their dams immediately after insemination. All cows that returned to estrus before pregnancy diagnosis were re-inseminated 12 h after estrous detection. Pregnancy diagnosis was performed by transrectal ultrasonography 30 days after TAI, confirmed 60 days after the end of breeding season. The pregnancy rate at end of the breeding season was calculated by dividing the number of pregnant cows heifers by the number of cows used in the breeding season. [...](AU)

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