Effect of Level of Energy Intake and Influence of Breed and Sex on Muscle Growth and Distribution in the Bovine Carcass

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Abstract
Growth and distribution of muscle in the trunk, and thoracic and pelvic limbs were studied in 141 cattle ranging in slaughter weight from 121 to 706 kilograms. Holstein and Angus bulls, steers and heifers were fed at two levels of energy: ad libitum and 65 to 70% of ad libitum. The allometric equation Y = aXb was used to examine the effects of energy intake and of breed and sex on the rate of muscle growth of the three joints relative to the carcass side or to total muscle in the carcass side. Group comparisons of muscle distribution in the three joints were made after adjustment by regression to a total muscle weight of 53.1 kilograms. In both breeds, and irrespective of the level of energy intake, sex did not influence (P>.05) growth rate of muscle in the thoracic and pelvic limbs relative to the carcass side or to total muscle. However, sex was found to affect growth rate of muscle in the trunk relative to the carcass side. Generally, neither level of energy intake nor breed altered (P>.05) growth rate of muscle in the three joints relative to the carcass side or total muscle. The distribution of muscle in the three joints adjusted to a total muscle weight of 53.1 kg was generally not influenced (P>.05) by sex or altered (P>.05) by the level of energy intake. Breed influenced (P<.05) the distribution of muscle in the trunk and pelvic limb; however, the commercial importance of this difference is questionable.