Dose-dependent effects of exogenous porcine somatotropin on the yield, distribution, and proximate composition of carcass tissues in growing pigs2

Abstract

Dose-dependent effects of porcine somatotropin (pST) on mass, distribution, and proximate composition of carcass tissues were investigated in 46 growing pigs. Barrows, weighing 30 +/- 1 kg, were assigned to five treatment groups to receive 0, 50, 100, 150, or 200 micrograms of recombinant pST/kg BW per day until pigs individually reached the 90-kg slaughter weight. Left carcass sides were fabricated into whole-sale cuts that were separated into muscle, adipose tissue, bone, and skin. Despite the reduction in dressing percentage, total muscle mass of the side was significantly increased by 3.9 to 5.7 kg (28 to 36%) by the lowest and highest doses of pST, respectively, whereas adipose tissue mass was decreased by 4.4 to 8.6 kg (38 to 74%). Bone mass was increased by 8 to 27% (P < .05), and skin mass was increased by 16 to 38% (P < .01) across the dose range. Distribution of carcass weight among the wholesale cuts was altered by pST toward lower proportions in the belly, jowl, and fat trimmings and greater proportions in the four lean cuts. Porcine somatotropin substantially reduced lipid concentration in all muscle groups in a dose-dependent manner, resulting in increased protein and moisture concentrations (P < .05). Adipose tissue lipid concentrations were reduced to an even greater extent at each dose. The progressive increase in muscle mass observed with pST doses > 50 micrograms/kg BW was less than the associated decrease in adipose tissue mass, indicating that a dose range of 50 to 100 micrograms/kg BW per day may be optimum for improving carcass value.