Relationship of Lactation Energy Intake and Occurence of Postweaning Estrus to Body and Backfat Composition in Sows

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Abstract
Forty-five crossbred primiparous sows were used to determine the relationship of lactation energy intake and the occurrence of postweaning estrus to (1) body fat (percentage), (2) lean body mass (LBM) and (3) qualitative and quantitative characteristics of adipose tissue. Sows received 8 (Lo) or 16 (Hi) Meal of metabolizable energy (ME)/d during lactation and 5.4 Meal of ME/d postweaning. Serum samples were obtained 1 d before weaning (d 0) and analyzed for creatinine and urea-N (indices of muscle and amino acid catabolism, respectively). Subcutaneous adipose tissue samples were obtained and analyzed for total lipid and myristic, palmitic, palmitoleic, stearic, oleic and linoleic acids. Last rib backfat thickness determined at weaning was used to estimate body fat (percentage). Lean body mass was estimated from 48-h creatinine excretion rates determined on d 15 and 16 postweaning. Sows fed the Lo diet that returned (Lo-R) and did not return (Lo-NR) to estrus by d 14 postweaning lost more (P<.01) weight during lactation, gained more (P<.01) weight postweaning, had higher (P<.07) body fat (percentage) and a slight trend toward lower creatinine excretion rate than sows fed the Hi diet that returned to estrus (Hi-R). Adipose tissue from sows in the Lo-R and Lo-NR groups had less (P<.05) lipid than that from sows in the Hi-R group. Concentrations of oleic and stearic acids were lower and higher (P<.01), respectively, in adipose tissue from sows in the Lo-R and Lo-NR vs Hi-R groups. Sows in the Lo-R group had similar (P>.10) lactation weight loss, weight gain postweaning, serum urea-N and creatinine concentrations, creatinine excretion rate and adipose tissue characteristics, but more (P<.01) body fat (percentage) at weaning than sows in the Lo-NR group. The data indicate that catabolism of body fat was more deleterious to a rapid return to estrus than was catabolism of muscle tissue and that the lack of estrous activity by d 14 postweaning cannot be explained by changes in adipose tissue composition. Copyright © 1984. American Society of Animal Science . Copyright 1984 by American Society of Animal Science.

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