Mechanism of Action of Beta Adrenergic Agonists and Potential Residue Issues

Bradley J. Johnson, Ph.D. Texas Tech University Department of Animal and Food Sciences [email protected] I.β-Adrenergic Agonist-Stimulated Muscle Hypertrophy One of the most pronounced effects of feeding a β2-adrenergic agonist to ruminants is the preferential increase in skeletal muscle mass and/or cross-sectional area of individual muscles. Examples of these skeletal muscle-enhancing characteristics are summarized in Table 1. Generally, addition of either clenbuterol or cimaterol, both presumed β2-adrenergic agonists, to ruminants resulted in increased longissimus muscle cross-sectional area between 11 and 39 %. In addition, the mass of selected muscles were increased between 8 and 40 %. These data suggested that addition of these β2-adrenergic agonists to ruminants resulted in dramatic increased muscle mass.