Effect of metabolism modifiers on lipid metabolism in the pig.

Porcine somatotropin (pST) and certain beta-adrenergic agonists are potent metabolic modifiers that can improve performance in pigs. Pigs treated with either compounds utilize feed more efficiently and are leaner than controls. Comparative slaughter data clearly demonstrate that pST and some beta-agonists stimulate protein deposition. Porcine somatotropin decreases lipid deposition, but this is not the case for all beta-agonists. Somatotropin decreases lipid deposition through decreasing adipose tissue sensitivity to insulin, inhibiting lipogenesis, and perhaps stimulating lipolysis. Although lipolysis is increased during pST treatment of growing pigs, the greatest consequence is decreased lipogenesis. Although under controlled conditions certain beta-agonists stimulate lipolysis and inhibit lipogenesis, the limited metabolic studies suggest that at doses that are most efficacious for enhanced protein deposition, there are limited effects on lipid metabolism. In part, this may be due to desensitization of adipose tissue beta-adrenergic receptors and possibly a consequence of antagonism of beta-receptors.