Carcase characteristics
Double-muscled cattle are known to have many superior carcass characteristics compared to normal cattle. This is mainly due to the generalised muscular hyper trophy, fineness of bones, lower potential to accumulate fat and smaller digestive tract of the double-muscled cattle. The superiority of double muscled carcases is reported to be mainly due to a higher dressing percentage, a larger proportion of muscle, and lower proportions of fat and bone in the carcase (). Thiessen (1974) reported up to 30% higher muscle : bone ratio in double-muscled carcases than in normal carcases.
Modification to the body composition of double-muscled animals is not uniform throughout the body. There are 'highly hypertrophied', 'hypertrophied' and muscled cattle are made at constant muscle weight (). In the rachidial region, the muscular hyper trophy seems to follow an anterioposterior gradient () where the minimum hyper trophy will be located around the neck. Muscular hyper trophy is more marked in hindlimbs than in forelimbs (). The muscular hypertrophy is also seen to affect peripheral muscles and those exhibiting a large superficial face (). From another angle, the muscular hypertrophy follows a distoproximal gradient () and tends to be maximum at the level of the first brachial and crural segments (). The non-uniform hypertrophy of the muscles results in carcases of double muscled animals having a higher proportion of 'expensive' cuts of meat relative to carcases of normal cattle.
Bones of the limbs are subject to a reduction according to the same gradient (). The general gradients of muscular hypertrophy and skeletal hypo trophy in double muscled cattle are presented in Fig. 1. Morphological differences in size and shape of long bones have been reported between double muscled and normal cattle. Wrist (1929) found limp bones of double-muscled cattle to be shorter and of decreased density. Vissac (1968) reported that shafts of lone bones of double muscled cattle were more slender but had larger epiphyses. Hendricks et al.(1973) reported lighter and shorter bones that had thinner cortices in double muscled muscled cattle.
The lower fat content of double muscled carcases is well documented (). Prominence is usually given to the hyper development of the musculature, however discriminant analyses indicate that the hypo development of the fatty tissue is more important than the hyper development of the muscles muscles in characterising the syndrome(). The study by Bailey et al.(1982) indicated that the hypo development of the fatty tissue is the result of a reduction in the volume of fat cells rather than a decrease in fat cell numbers.