Efeito do diâmetro folicular e manifestação de estro sobre o desempenho reprodutivo de vacas nelore submetidas à IATF

Abstract

The objective of the present study was to evaluate the reproductive performance of lactating Nelore cows submitted to TAI considering the follicular diameter and estrus manifestation. Thus, the possible practical implications of the use of this information for the improvement of TAI programs in lactating zebu females were evaluated. This study is divided into 2 parts. In the first part, it was evaluated the associations between the follicular diameter at the end of the synchronization protocol, in the occurrence of estrus and concepyion rate ofNelore cows submited to TAI. It was observed that cows with larger follicles diameter, measured at the time of TAI, were more likely to show estrus and become pregnant. The second part, it was evaluated the importance of the occurrence of estrus and the administration of GnRH at the time of TAI and it was observed that the occurrence of estrus, evaluated by the removal of the ink at the base of the tail, was an important factor associated with improvements in conception rate of lactating Nelore cows, as well as administration of GnRH in cows that did not show estrus, favored an increase in conception rate. ECC influenced conception rate in the control group, but not in cows receiving GnRH. The number of uses of the P4 device affected the occurrence of estrus, as well as the rate of conception. Bull also influenced conception rate. Thus, alternatives should be adopted with the aim of increasing the diameter of the ovulatory follicle, favoring the efficiency of the protocols of artificial insemination at fixed time.