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Relationship between Body Fat and Postweaning Interval to Estrus in Primiparous Sows¹

Michigan State University, East Lansing 48824

Abstract

Twenty-two primiparous Yorkshire sows were used to determine whether a minimal threshold of body fat exists below which the return to estrus is delayed. A second objective was to examine the relationship between body fat and interval from weaning to estrus in restricted-fed sows. During lactation (28 d), sows received 7, 9, 11 or 13 Meal of ME daily to produce a range of sow body fatness at weaning. Intake of all dietary essentials except ME was similar for all sows. Litter size was adjusted to 10 pigs for all sows by d 3 postpartum. Each day from weaning to estrus, sows received 110 kcal ME per kg metabolic body weight plus 1,359 kcal ME per sow. Body fat was estimated at weaning and at first postweaning estrus by deuterium oxide dilution. Last rib backfat depth was determined ultrasonically 24 h postpartum and at weaning. Irrespective of dietary ME intake, percentage body fat at weaning (R² = .24; P < .05) and first postweaning estrus (R² = .03; P > .50) accounted for only a small portion of variation in interval from weaning to estrus. Likewise, loss of backfat depth during lactation was not an accurate predictor of interval from weaning to estrus (R² = .24; P < .05). The low coefficients of determination (<.25) suggest that body fat is a minor controller of postweaning interval to estrus. In contrast, dietary ME intake during lactation accounted for the largest portion of the variation (R²; = .48; P < .01) in postweaning interval to estrus. We conclude that timing of postweaning estrus in primiparous sows is not dependent on a minimal threshold of body fat. Furthermore, effects of lactational ME intake on the postweaning interval to estrus are more pronounced than the effects of body fat.

¹ Agric. Exp. Sta. Journal Article No. 12490.

² Dept. of Anim. Sci.

³ Dept. of Large Anim. Clin. Sci.

⁴ To whom reprint requests should be sent.