Historical Overview of the Effect of -Adrenergic Agonists on Beef Cattle Production.
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Postnatal muscle hypertrophy of beef cattle is the result of enhanced myofibrillar protein synthesis and reduced protein turnover. Skeletal muscle hypertrophy has been studied in cattle fed -adrenergic agonists (-AA), which are receptor-mediated enhancers of protein synthesis and inhibitors of protein degradation. Feeding -AA to beef cattle increases longissimus muscle cross-sectional area 6% to 40% compared to non-treated cattle. The -AA have been reported to improve live animal performance, including average daily gain, feed efficiency, hot carcass weight, and dressing percentage. Treatment with -AA increased mRNA concentration of the 2 or 1-adrenergic receptor and myosin heavy chain IIX in bovine skeletal muscle tissue. This review will examine the effects of skeletal muscle and adipose development with -AA, and will interpret how the use of -AA affects performance, body composition, and growth in beef cattle.