GnRH agonists: Updating fixed-time artificial insemination protocols in sows.

Protocols for fixed-time artificial insemination (FTAI) in swine reproduction can help increase genetic improvement and production efficiency. Different gonadotropin-releasing hormone (GnRH) agonists have been developed to gain better control of follicular development, timing, and ovulation quality; therefore, they have been extensively used in FTAI protocols. This literature review resumes the most important characteristics of the physiology of follicular development and ovulation in sows, followed by a discussion about the hormonal alternatives available to induce ovulation (human chorionic gonadotropin, hCG; porcine luteinizing hormone, LH and GnRH agonists). Also, ovulation induction failures with GnRH agonists are described. Finally, current FTAI protocols with GnRH agonists are resumed and discussed. FTAI with GnRH agonists has proven to be an efficient, successful reproductive protocol that can be implemented in pig farms due to better knowledge of an endocrine system that regulates follicular development and ovulation and increased availability of several GnRH agonists that allow more efficient reproductive swine programs.