Technologies for fixed-time artificial insemination and their influence on reproductive performance of Bos indicus cattle.

The adaptation of Bos indicus cattle to tropical and subtropical environments has led to their widespread distribution around the world. Although artificial insemination (AI) is one of the best alternatives to introduce new genetics into Bos indicus herds, the peculiarity of their temperament and the tendency to show short oestrus (many of them during the night) greatly affects the effectiveness of genetic improvement programs. Therefore, the most useful alternative to increase the number of females that are inseminated is the use of protocols that allow for AI without the need for oestrus detection, usually called fixed-time AI (FTAI). Besides, the development of protocols to advance the resumption of cyclicity during the early postpartum period has a great impact on beef production and will allow for the inclusion of a significantly larger population of animals into genetic improvement programs. Fixed-time AI protocols using progestin devices, oestradiol and eCG have resulted in consistent pregnancy rates in suckled Bos indicus and Bos indicus x Bos taurus cows. Furthermore, fertility in the successive cycles and the overall pregnancy rates at the end of the breeding season, have been shown to be improved by the use of progestin devices at the beginning of the breeding season. In summary, exogenous control of luteal and follicular development has facilitated the application of assisted reproductive technologies in Bos indicus-influenced cattle, by offering the possibility of planning programs without the necessity of oestrus detection and may provide the opportunity to improve reproductive performance of beef cattle in tropical climates.