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Title: THE INFLUENCE OF THE WEANING-TO-BREEDING INTERVAL AND OVULATION RATE IN PARITY-TWO SOWS

Author
item DECKERT, ANNE - UNIVERSITY OF NEBRASKA
item DEWEY, CATHERINE - UNIVERSITY OF NEBRASKA
item Ford, Johny
item STRAW, BARBARA - MICHIGAN STATE UNIVERSITY

Submitted to: Swine Health and Production
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: When sows are mated at the first estrus after weaning of their litters, subsequent litter size varies in relation to the number of days from weaning to estrus. Subsequent litter size is optimal when the sow is bred on days two to five after weaning, decreases progressively in sows that do not show estrus until days five, six, or seven, and remains low for sows that show estrus on days eight, nine and ten after weaning. In the curren study, ovulation rate decreased as the interval from weaning to estrus increased. Thus, we concluded that changes in ovulation rate contribute significantly to the previously reported changes in litter size. These observations are valuable to producers and consultants as they evaluate technologies to improve litter size.

Technical Abstract: Litter size is optimal when the sow is bred two to four d post-weaning and then decreases daily from d five through seven. Litter size stays low for sows bred on d eight through 10 post-weaning, rises on d 11, and remains at an intermediate level through d 14. This study used 376 white crossbred sows that were slaughtered at 28 to 33 d of gestation and the ovaries dissected to determine the number of corpora lutea. Average ovulation rat was 13.32 +/- .32 ova. The mean weaning-to-breeding interval for the study was 5.88 +/- .14 d. Ovulation rate increased by .31 +/- .08 ova as the number of piglets weaned in the sow's previous parity increased by one piglet (P < .001). Population line, parity and season the sow was weaned were also associated with ovulation rate (P < .001). Compared to sows with weaning-to-breeding intervals for four or five d, ovulation rate decreased by .99 +/- .38 ova for sows with weaning-to-breeding intervals of six d, and decreased by 2.17 +/- 1.09 for sows returning ten to twelve d post-weaning (P < .05). This relationship explains part of the association between weaning-to-breeding interval and litter size.