Historical Overview of the Effect of β-Adrenergic Agonists on Beef Cattle Production

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 beta-adrenergic agonists (beta-AA), which are receptor-mediated enhancers of protein synthesis and inhibitors of protein degradation. Feeding beta-AA to beef cattle increases longissimus muscle cross-sectional area 6% to 40% compared to non-treated cattle. The beta-AA have been reported to improve live animal performance, including average daily gain, feed efficiency, hot carcass weight, and dressing percentage. Treatment with beta-AA increased mRNA concentration of the beta(2) or beta(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 beta-AA, and will interpret how the use of beta-AA affects performance, body composition, and growth in beef cattle.