Carcass composition of double-muscled cattle

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Abstract
1. An anatomical explanation of the observed differences between double-muscled and phenotypically normal cattle was sought by detailed dissection of the sides of six double-muscled Santa Gertrudis steers and six Brangus steers.2. Relative to carcass weight the double-muscled steers had a significantly greater proportion of muscle and a significantly lower proportion of bone and fat than the Brangus steers. Relative to muscle plus bone weight the muscle proportion was greater and the bone proportion lower in the double-muscled steers.3. The musculature of the double-muscled steers exhibited a gradient of hypertrophy: 12 muscles (234g/kg of total muscle weight) were grossly hypertrophied, 56 muscles (565g/kg) were hypertrophied to a lesser degree and 28 muscles (195g/kg) showed either a minor degree of hypertrophy or no hypertrophy.4. The grossly hypertrophied muscles were generally the larger, superficial muscles of the proximal pelvic limb and shoulder area. The muscles showing least hypertrophy were mostly small muscles located in the deeper areas of the carcass, particularly around the spine and in the proximal hindlimb, and in the proximal and distal forelimb.5. Abnormalities of shape in double-muscled cattle may be attributed largely to altered proportions of total muscle and total fat, and to changes in weight distribution within the musculature.