Inseminação artificial em tempo fixo e diagnóstico precoce de gestação em vacas leiteiras mestiças

Abstract

It was evaluated, during a period of one year, the reproductive performance of 94 Bos taurus × Bos indicus crossbred dairy cows submitted to an assisted reproduction program. A timed artificial insemination (TAI) protocol was carried out by using an intra-vaginal progesterone device containing progesterone and through injections with Prostaglandin F2α and estradiol cypionate. By using ultrasound, from 7 to 14 days after inseminations or controlled mattings, detection of corpus luteum in the ovaries was done to determine ovulation rate and, on the 28th day, diagnosis of pregnancy was carried out for calculation of conception rate. Treatment only started after a 34-day post-partum minimal period. Body condition score, presence of corpus luteum in the beginning of the protocol, reutilization of intra-vaginal device and controlled mating or artificial insemination did not influence rates of ovulation, conception and conception of ovulated cows. Rates of conception and rates of conception of ovulated cows were negatively affected by the higher number of days post partum (DPP), or days in milk and by the warmer seasons of the year, spring/summer. Response to protocol of timed artificial insemination based on the use of progesterone, PGF2α and estradiol cypionate is negatively affected by lactation days and by the warm season of the year. Body condition does not affect the response to protocol of artificial insemination provided that treated cows show body condition scores higher than 2.5 points. © 2011 Sociedade Brasileira de Zootecnia.