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J Anim Sci. 1989 Oct;67(10):2576-88.

Relationship between fasting heat production, body composition and tissue distribution, in mature ewes from seven breeds.

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  • 1University of Nebraska Lincoln.


To evaluate the relationship between measures of maintenance and body composition, data were collected on 12 mature, nonpregnant, nonlactating ewes from each of seven breeds following 6 wk of ad libitum (AL) or maintenance (MN) feeding (six per breed-level). After fasting 56 h, fasting heat production (FHP) was measured for each of 42 pairs of ewes over a 16-h period. Ewes then were slaughtered and the empty body divided into visceral organs and blood (ORB); gastrointestinal tract and internal fat (GIF); head, hooves and pelt (HHP); and carcass (CAR). Each fraction was chemically analyzed for water, fat, ash and (by difference) fat-free dry organic matter (FFDOM or protein). Correlations with FHP/d were highest (.86 to .87) for weights of empty body and body water or lean (FFDOM + water) and were lower (.77) for weight of empty body fat. Best nonlinear LWT predictors of FHP/d were LWT.63 and water.71 or lean.71 (R2 = .76). Correlations of metabolic FHP (kcal/kg.75) with percentage lean and fat, respectively, were .53 and -.55 for the empty body and .60 and -.60 for the GIF fraction. For AL ewes, the better predictors of FHP/d were weights of lean in GIF + ORB (R2 = .88, ESD = 106), live weight (LWT) plus fat and lean in GIF fraction (R2 .88, ESD = 112) or LWT plus fat in HHP and GIF fractions (R2 = .90, ESD = 103). For MN ewes, LWT alone was as accurate (R2 = .80, ESD = 123) as any combination of components. Breed mean daily FHP was predicted very accurately (R2 = .94) from total weight of empty body lean plus the proportion of total body lean located in the GIF fractions.

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