Influence of breed and sex on muscle weight distribution of cattle

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Abstract
Summary: In this experiment an attempt was made to study the influence of breed and sex on the muscle-weight distribution of cattle. The weights of individual muscles obtained by total dissection from the side of a carcass from each of 63 bulls, 106 steers and 22 heifers representing six, eight and two breed groups respectively were classified into nine anatomical groups using the method of Butterfield (1963). Muscle-weight distribution was then studied by expressing the muscle in each of these groups as percentages of total muscle and also as adjusted mean weight of muscle in each region while statistically adjusting total muscle to a constant level.Results indicated that breed differences were significant although small for abdominal muscles and muscles of the neck region within bulls and steers, but two breed groups of heifers did not differ. There was no detectable breed influence on the percentage of any other muscle group. Percentages of muscles classified as expensive were found to be remarkably similar among breed groups in all three sexes.Sex influences on muscle distribution were also appraised. There was a general trend of heifers having a higher percentage in the proximal pelvic limb and abdominal areas than steers, while steers exceeded bulls. This order of sex influence was reversed in the muscles of the neck and thorax region. The influence of sex was conspicuous in areas classified as having expensive muscles, with heifers having a higher percentage of muscles in the high-priced regions than steers and steers being superior to bulls. Sex differences reflect the differential development of bulls compared with the other sexes as they mature. Muscles of the neck and thorax in bulls increase in proportion and other groups (proximal hind and abdominal) decrease. The differentiation of muscles represents a trend toward masculinity from heifer to steer to young bull and finally to old bull proportions.