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Puberty and Estrus in Confinement-Reared Gilts¹

U.S. Department of Agricultural^,3, Clay Center, NE 68933

Abstract

The physiological mechanisms responsible for puberty in mammals remain poorly understood despite many investigations. The incidence of gilts that did not show regular estrous cycles at 9 months of age ranges from 10 to 40% and breed of gilt is an important factor contributing to this percentage. The percentage of Landrace gilts that showed regular estrous cycles at 6 months of age was higher (P<.01) than that of Hampshire, Large White, Yorkshire and Duroc gilts. Estrous activity for these five breeds of gilts at 8.5 months of age had reached a plateau and a higher percentage of Landrace, Large White, Hampshire and Duroc gilts showed regular estrous cycles than did Yorkshire gilts (78, 86, 71, 71 vs 56%, respectively). Of the noncyclic gilts slaughtered at 9 months of age, 55% were gilts with immature reproductive tracts (delayed puberty) and 45% were gilts with fully developed uteri and ovaries that had corpora lutea at different stages of development or preovulatory follicles and corpora albicans (behavioral anestrus). Behavioral anestrus can be reversed by methallibure treatment. Season of year and social environment, in addition to breed, influence puberty and regularity of estrous cycles in confinement-reared gilts, but the relative influence of each remains to be determined.

¹ Invitational paper presented at the 11th Meeting of the Midwestern Section ASAS, Southern Illinois Univ. Carbondale, January 5, 1978. Original research supported in part by USDA Cooperative State Research Service grant 701-15-42, USDA, Science and Education Administration-Agricultural Research, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, NE; and Department of Animal Science, Nebraska Agr. Exp. Sta., Lincoln, NE.

² The authors express their appreciation to the swine operation personnel of the Roman L. Hruska U.S. Meat Animal Research Center for their assistance.

³ Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.