Current concepts in estrus synchronization in swine

Several managerial and pharmacological methods are available for porcine estrus synchronization. Before implementing a method, producers must have a clear idea of the goal of estrus synchronization and a realistic expectation of the outcome. Induction of precocious puberty in gilts is perhaps the most economically favored estrus synchronization technique available to swine producers. Appropriately applied boar exposure and judicious use of gonadotropins are effective methods to improve productivity in breeding herds by reducing the number of days required for gilts to farrow their first litter. Proper management of sows during lactation and at weaning offers an excellent method to have synchronized estrus to facilitate rebreeding and the incorporation of an artificial insemination program. Gonadotropin treatment is also useful in sows at weaning to prevent delayed return to estrus associated with season and parity. Although not currently approved for use in the United States, the orally active progestogen “altrenogest” is effective for producing synchronization of estrous cycles in swine and would potentially facilitate synchronization of cycling sows and gilts. Alternative dose and duration protocols combined with PGF2α may offer even more efficient and profitable uses of this hormone. Elective abortion or the establishment of pseudopregnancy followed by PGF2αinduced luteolysis will reliably synchronize estrus in gilts, but neither hormone is approved for this purpose. Research efforts to develop effective methods of estrus control will continue in order to support the increasingly mechanized and efficient swine enterprises of the future. Hormone-impregnated implants, pessaries, or biodegradable microspheres are potentially useful due to their improved labor efficiency compared with multiple-dosing protocols and are likely to be incorporated into future estrus synchronization programs.