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Influence of Duration of Litter Separation and Boar Exposure on Estrous Expression of Sows during and after Lactation¹

Kansas State University⁴, Manhattan 66506

Abstract

The influence of litter separation (LS) that included a change in housing environment and social status of sows, boar exposure (BE), and parity on estrous expression by sows during and after lactation was examined in two experiments utilizing 140 crossbred sows. In Exp. 1 (Yorkshire x Duroc sows), limiting duration of LS to 6 or 3 h/d during the last 8 d of lactation in two trials, while maintaining 1 h BE, resulted in similar proportions of sows in estrus during lactation (65 vs 79% for 3- and 6-h sows). However, 6-h LS tended to reduce (P=.O8) the interval to estrus by .6 d for those sows that expressed a preweaning estrus. Postweaning intervals to estrus were unaffected by duration of LS in the remaining sows. In Exp. 2, sows (Yorkshire x Duroc x Chester White) were assigned to four treatment groups during the last 8 d of lactation: 1) BE (1 h/d), 2) LS (6 h/d), 3) LS + BE and 4) no LS + no BE (control). Only nine sows expressed estrus during lactation; four of 28 LS sows and five of 28 LS + BE sows. No sows were in estrus before weaning during August 1985 and only one sow (LS group) was in estrus before weaning during October 1986. Postweaning intervals to estrus were reduced (P<.05) by .9 d after preweaning BE compared with controls. These data suggest that: 1) 6 h of LS may reduce the interval to estrus in sows that express estrus during lactation but 3 h is sufficient to induce estrus in equal proportions of sows, 2) BE was not sufficient to induce estrus during lactation, 3) preweaning BE reduced postweaning intervals to estrus and 4) breed composition may alter the responsiveness of sows to stimuli that induce lactational estrus.

¹ Contribution no.87-205-J, Kansas Agric. Exp. Sta., Manhattan 66506. The authors acknowledge the assistance of T. Jewett, M. Trehan and J. Carpenter at the Kansas State Univ. Swine Teaching and Res. Center. We also thank K. Minneman and L. Schinstock for typing this manuscript.

² Present address: Dept. of Anim. Sci., Ohio State Univ., Columbus, OH 43210.

³ Address reprint requests to this author.

⁴ Dept. of Anim. Sci. and Ind.

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