Somatotropin alters collagen metabolism in growing pigs

Treatment of pigs with porcine somatotropin (pST) is associated with altered nutrient partitioning. The aim of this investigation was to determine the role of pST in protein and collagen deposition in growing pigs. Barrows were treated daily with buffer or pST when they weighed between 30 and 64 kg (n = 8 pigs/group). Pigs were restrictively fed such that the average feed intake for both groups was 1.86 kg/d. Treatment with pST was associated with 25, 55, 78 and 31% higher growth rates for carcass, skin, viscera and head, respectively. Total protein depositions (g/d) were 52, 60, 81, 42 and 54% greater in carcass, skin, viscera, head and empty body, respectively, of pST-treated pigs. Collagen represented approximately 70, 15 and 43% of total protein in skin, viscera and head; pST did not influence this ratio. However, collagen relative to total protein was 16% lower in the carcass of pST-treated pigs. Deposition rate of collagen was higher in all components of empty body, except carcass, as a result of pST treatment. The ratio of non-collagen protein to collagen deposition rate was 49% greater in the carcass of pST-treated pigs. The deposition rate of acid-soluble collagen was approximately 2-fold higher in skin but was 25% lower in carcass of pST-treated pigs. Depositions of insoluble collagen in viscera and head of pST-treated pigs were 74 and 46% greater, respectively, than for controls. These data show that pST treatment enhances collagen deposition in skin, head and viscera, whereas non-collagen protein deposition and collagen maturation are enhanced in the carcass.