Influence of Age, Nutrition and Genotype on Carcass Traits and Cellular Development of the M. Longissimus of Cattle

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Abstract
Growth of the M. longissimus was studied in cattle of two genotypes fed ad libitum or limited-fed to reduce growth rate 33%. Steers from Charolais and Angus bulls were slaughtered at 110, 220, 360 and 500 kg body weight. Growth of half the cattle slaughtered at 360 and 500 kg was reduced by limiting feed intake starting at 220 kg body weight. From 110 to 360 kg body weight, the weight of the M. longissimus, quantity of DNA, protein and lipid in the muscle, and protein/DNA ratio increased 3.0-, 2.7-, 3.2-, 9.0- and 1.2-times, respectively. From 360 to 500 kg body weight, the respective increases were 1.2, 0, 1.2, 3.8 and 1.3. From earliest to latest, the order of maturing as measured by the growth coefficient relating the measured parameters of muscle growth with body weight was protein/DNA, DNA, protein and lipid. When compared at similar live weights, the weight of the M. longissimus, amounts of DNA and protein and protein/DNA were similar in the two genotypes. Limiting growth by level of feeding decreased the rate of accumulation of DNA and protein in the muscle, but had no effect on the measured growth parameters when the limited-fed cattle were slaughtered at the same body weights as the full-fed controls. No significant differences were obtained for carcass traits when the restricted and ad libitum groups were compared. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.