REDEFINING BODY COMPOSITION: Nutrients, Hormones, and Genes in Meat Production

Abstract

Growth rate and body composition of livestock can be optimized to meet consumer needs for a leaner product and to improve the efficiency of meat-animal production. Optimization strategies have traditionally focused on genetic selection and cost-effective ration formulation to achieve the genetic potential. Advances in understanding the mechanisms of growth and its control have led to additional opportunities for its manipulation. These include nutritional manipulation,the use of growth promotants, and, more recently, the ability to change the genetic potential through genetic engineering. Selection of appropriate candidate genes for manipulation depends on understanding the mechanisms underlying differentiation and growth of embryonic muscle cells. Recent advances in genetic engineering techniques, including gene therapy and germline transgenesis, will likely hasten the genetic progress toward a leaner carcass in domestic livestock. Such strategies may prove to be more beneficial then the controlled enhancement of somatotropin expression.

Hormones et promoteurs de croissance en productions animales : de la physiologie à l’évaluation du risque

“…Après la naissance, le rôle des hormones hypophysaires dans le contrôle physiologique de la croissance est bien établi (Wray-Cahen et al 1998). Les principaux tissus placés sous le contrôle de la GH sont le muscle, le tissu adipeux et aussi le foie et le tissu osseux (figure 2).…”

“…La fonction de lactation, en permettant une meilleure adaptation des mam- (Wray-Cahen et al 1998, Meyer 2001. L'équilibre entre ces systèmes détermine le niveau d'utilisation des nutriments pour la fonction de croissance.…”

Regulation of gene expression by ractopamine in porcine skeletal muscle

“…Carcass dressing percentage, longissimus muscle area, dissected carcass lean, and estimated fat-free muscle percentage increased in a dose dependent manner, while the undesirable carcass traits of carcass fat depth, average backfat, and dissected fat decreased after feeding ractopamine. Others have reported similar findings (Moody et al, 2000;Wray-Cahen et al, 1998). These responses are consistent regardless of sex (Dunshea et al, 1993b;Uttaro et al, 1993;Williams et al, 1994), genotype (Bark et al, 1992Gu et al, 1991;Yen et al, 1990;, and final slaughter weight(Crome et al, 1996} of the ractopamine treated pigs.…”