The review work is based on analyzing and recording the effects of the application of ovulation synchronization protocols based on gonadotropin-releasing hormone (GnRH) and insulin for the increase of the pregnancy rate in crossbred Holstein cows in research published between 2013 and 2017. The study was conducted through the integrated search of relevant authors’ research using key criteria of both inclusion and exclusion, with results from 244 articles analyzed, where 118 analyzed the interaction of energy balance and ovulation of dairy cows. Fifty-three articles relate the effective ovulation synchronization protocol for the luteal process and 73 articles analyze the effect of insulin in the luteal process; and finally 18 articles are important to address the problem; insulin can be altered as a metabolic hormone by the increase of fat components of the feed ration consumed by cows, thus influencing ovarian function; ovulation synchronization is necessary, which can be based on GnRH and insulin.
Part of the book: Estrogen