J. Anim Sci.
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J. Anim Sci. 1986. 62:9-15.
© 1986 American Society of Animal Science
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Effect of Boar Presence Before and After Weaning on Estrus and Ovulation in Sows

J. S. Walton1

University of Guelph,2, Ontario, Canada N1G 2W1

Abstract

Two hundred sixty-two sows were used to investigate the effects of boar exposure during the last week of nursing (BPRE) and after weaning (BPOST) on the return to estrus. Because approximately one-half of the sows were weaning their first litter, a third factor, primiparous vs multiparous (LITT), was considered in the statistical analysis. To evaluate the effect of treatment on ovarian activity, the sows were also blood-sampled twice weekly for 3 wk after weaning for the measurement of plasma progesterone concentrations as an index of ovulation. Boar exposure after weaning was the most important stimulus of early ovulation and estrus after weaning (P<.001). A greater proportion of first-litter sows exhibited estrus later (P<.02) and ovulated later (P<.09) than did multiparous sows. First-litter sows were unaffected (P>.10) by boar exposure before weaning. Multiparous sows were sensitive to boar exposure during nursing. Maximal boar exposure for these sows (BPRE + BPOST) resulted in 95% of sows in estrus and ovulating within 20 d of weaning. No boar exposure resulted in 45% and 38% anestrus and anovulatory sows. Boar exposure, either before or after weaning, was effective in reducing the number of anestrus and anovulatory sows to between 15 to 30%. The effects of BPRE and BPOST on return to ovulation were additive and approximately equal.

Footnotes

1 The author acknowledges the excellent technical assistance of R. Weston, B. Szkotnicki and M. E. Clark. Financial support was provided by the Ontario Pork Producers Marketing Board and the Ontario Ministry of Agriculture and Food.

2 Dept. of Anim. and Poul. Sci.






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Copyright © 1986 by the American Society of Animal Science.