Bovine Muscularity: Its Relationship to Feed Efficiency

Abstract
Forty-eight steers varying in degree of muscling (angular to bulging) and genotype (Angus, Brown Swiss, Charolais, Holstein, Longhorn, crossbred, double muscled) were selected to represent five shape groups. Seventeen steers served as controls and were slaughtered to estimate the initial composition of the cattle to be fed. The remaining 31 were individually full fed for 132 days. During slaughter, weights of all parts were combined to determine live empty body weight (LEBW) which excluded ingesta and excreta for establishing standardized dressing percentages. All soft tissues were homogenized to provide samples for drying and ether extraction to establish quantity of fat-free muscle (FFM). Using standardized dressing percentages and percentage of FFM of the controls, the gain in FFM was calculated for the experimental groups. Using the increased FFM with feed consumed during the test period, efficiency values were expressed as kilograms feed required to produce 1 kg FFM. Means for five shape groups were subjected to analysis of covariance. When LEBW and percentage fat of LEBW were held constant, visually appraised muscling (shape) of the live animal starting on test did not significantly affect the conversion of feed to FFM. As anticipated, fatter animals required more feed to produce FFM (P<.01). Shape per se did not affect feed efficiency. However, muscular animals are leaner at a given chronological age and are, for this reason only, more efficient converters of feed to FFM. Copyright © 1977. American Society of Animal Science . Copyright 1977 by American Society of Animal Science.

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