U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska


Date of this Version


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Published in Beef Research Program Progress Report (1993) No. 4 (Part 1): 135-136


It is well established that proteins are continually synthesized and degraded in skeletal muscle, but the proteolytic enzymes involved in muscle protein degradation remain unknown. It is hypothesized that the calpain proteolytic system, which is known to be important in postmortem protein degradation and thus in meat tenderization, could also be involved in or even possibly initiate muscle protein degradation in the living animal.

It is well documented that intact males grow more rapidly (15 to 17%), utilize feed more efficiently (10 to 13%) and produce higher yielding carcasses with less fat and more lean meat than castrates. However, the underlying mechanisms for these advantages have not been determined. The objective of this study was to determine the effect of gender (bull vs steer) on the relationship between muscle enzyme activity and muscle protein turnover in growing cattle.