Influence of Weight and Nutrition upon Muscle Growth and Intramuscular Fat Deposition in Holstein Steers

Abstract
Muscle growth coefficients calculated on a fresh, fat-free or fat and moisture-free basis were not significantly different between “high” and “medium” nutritional levels for six of the seven muscles studied. Methods of expressing the muscle growth coefficients did not appear to alter the magnitude of the coefficients. Intramuscular fat depositions coefficients were not significantly different between the “high” and “medium” nutritional planes for any of the seven muscles studied. The intramuscular fat deposition coefficients for the “high” group suggested fat in the gluteus medius, semimembranosus and quadriceps had an earlier relative maturity compared to the biceps femorisand longissimus. Coefficients of intramuscular fat deposition were almost twice as large as the muscle growth coefficients. Comparisons of growth coefficients were also made by deleting the 91 kg. animals in the “high” and “medium” groups. Muscle growth coefficients of the “high-medium,” “medium-high” and “medium” groups were compared to the “high” group and no significant differences were noted. Again there were no large differences among coefficients expressed on a fresh, fat-free or fat and moisture-free basis. The coefficients of intramuscular fat deposition in the “high-medium” group were significantly lower than the coefficients in the “high” group for four of the seven muscles studied. This indicated that changing nutritional planes from “high” to “medium” could be used to regulate the rate of intramuscular fat deposition, without altering muscle growth rate, while merely restricting the nutritional level throughout growth may not be as effective in regulating intramuscular fat deposition. Only one muscle in the “medium” group and none of the muscles in the “medium-high” group had intramuscular fat deposition coefficients different from the “high” group.

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