Effects of the Beta-Adrenergic Agonist L-644,969 on Growth Performance, Carcass Merit and Meat Quality

The challenge to those seeking to discover ways to enhance growth of meat animals is established by the needs of the producer and the demands of consumers. In meat animal production, feed grains represent the single largest cost. Thus, a producer will adopt a production method or purchase a growth improver if it results in improved feed efficiency and therefore profits. But, in the United States, where most animals are purchased on a liveweight basis, producers are unlikely to purchase agents that promise only changes in carcass composition. Consumers are concerned about price and quality of meat. With respect to the latter, the major issue is quantity of fat associated with meat and meat products. Diets high in animal fats constitute a health risk and are unattractive to growing numbers of consumers who are healthand weight-conscious. In addition, deposition of fat on meat animals is wasteful and excess fats are trimmed and discarded at the processing plant or left uneaten by the consumer. Against this background, beta-adrenergic agonists are particularly attractive as growth improvers. They have the potential to improve feed efficiency and carcass fat/lean ratio in all meat animals: cattle (Hanrahan et al., 1986); swine (Jones et al., 1985); sheep (Baker et al., 1984) and poultry (Asato et al., 1984). This contrasts with products currently marketed for improving growth, i.e., steroid hormones are effective only in ruminant animals and antibiotic growth permittants are used only in monogastric animals. Some beta-agonists are orally active so “in-feed’’ formulations are possible. In addition, many beta-agonists are extremely potent and chemically stable, making successful development of implants for cattle, sheep and swine likely. This contrasts with the very difficult problem of formulating peptide hormones for the growth promotion market.