Application of Exogenous GnRH in Food Animal Production

Simple Summary Optimum fertility requires the deposition of sperm at the appropriate time relative to ovulation, which can be achieved by using gonadotrophin-releasing hormone (GnRH) to control the time of ovulation. Following insemination, the establishment and maintenance of pregnancy and embryo survival are promoted by progesterone released from the ovarian corpora lutea, also under the control of GnRH-stimulated gonadotrophin release. This review examines the effect of the application of GnRH on the productivity and fertility of food-producing animals. Over several decades, exogenous GnRH and agonists have been employed for controlling reproductive cascades in animals, and treating some reproductive morbidities. The administration of GnRH is used in animals to counter ovarian dysfunction, induce ovulation, and to increase conception and pregnancy rates. GnRH and its agonists are used in the treatment of cystic ovarian degeneration and repeat breeder syndrome. The development of protocols for GnRH administration by intramuscular injection, intramuscular or subcutaneous implants, and intravaginal deposition has empowered their clinical use worldwide. Currently, exogenous GnRH products are a central part of several pre- and post-breeding programs for the enhancement of fertility, including the control of estrous cycles and timing of ovulation, development of fixed-time artificial insemination protocols, improved embryo survival, and the treatment of reproductive morbidity. The aim of the present review is to summarize the application of exogenous GnRH agonists in food animal production.