Update on protocols for fixe-timed artificial insemination in sheep

Fixed–time artificial insemination (FTAI) in cattle has had a marked growth in South American countries in the last two decades, mainly based in the use of pharmacological treatments with estradiol and progesterone. To improve the pregnancy rate obtained with this technology, the focus has recently been on other aspects of the hormonal protocols that had not been considered previously. The most novel approaches propose studying preovulatory strategies to improve postovulatory conditions to improve pregnancy outcomes. In this paper we review the main results obtained by extending the proestrus length (i.e., the interval from progesterone removal to insemination). The results show that these new approaches allow an improvement in pregnancy rate, which deserves to be taken into account to be included in the implementation of FTAI programs.