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


Date of this Version


Document Type



Published in Beef Research Program Progress Report (1988) No. 3: 84-85


There is too much fat on beef carcasses today. Research in beef cattle production is directed towards solving this problem by maximizing partitioning of dietary nutrients to lean muscle growth and minimizing deposition of carcass fat. Partitioning agents called β - adrenergic agonists are able to cause this type of nutrient partitioning. Earlier work showed two of these compounds, clenbuterol and cimaterol, can be fed and are effective in many species including pigs, sheep, and cattle. At levels that did not depress gain, clenbuterol feeding increased protein content of the 9th to 11th rib section by 13% and decreased fat content by 20% in cattle. Even more dramatic carcass changes were observed in cattle in response to cimaterol.

Of interest are the underlying metabolic changes and controls that must be altered to bring about the carcass changes previously cited. To date, the mechanisms responsible for altering nutrient partitioning in response to β-adrenergic agonists are not well defined. The objectives of our study were to compare the initial and adapted effects of clenbuterol on blood flow, heart rate, and metabolism in the hindquarters of growing steers.