Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/1997
Publication Date: N/A
Citation: Interpretive Summary: Treatment of pigs with porcine somatotropin (pST) also called growth hormone (GH) has received considerable attention as a method for manipulating growth rate and enhancing lean meat production. Since body composition of pigs and rate of growth is altered, it is unclear whether pigs would respond to pST administration under all dietary conditions. This study was performed to investigate the influence of dietary protein on the growth response elicited by pST. 60 castrate male pigs (30kg) were fed 1 of 5 diets containing 11, 15, 19, 23 or 27% crude protein. Half of the pigs were injected daily (for 42 days) with recombinant pST donated by Pitman Moore and the 30 pigs were injected with saline. Growth rate was 23 % greater in pST-treated pigs fed 11% protein compared to respective controls. The stimulation of growth was between 42 and 56% in pST-treated pigs fed higher levels of protein. The efficiency of feed utilization was improved between 14 and 31% in pST-treated pigs compared to respective controls. Treatment with pST resulted in an overall increase in carcass protein by 12% and fat content was reduced between 19 and 41% in pST-treated pigs. Interactions were not observed in growth parameters comparing control and treated pigs. This suggests that pST-treated pigs respond to dietary protein similarly to controls. It is not likely that pST administration will impact upon protein requirement of young growing pigs.
Technical Abstract: Two experiments conducted with cross-bred barrows to determine the effect of somatotropin administration on liver and kidney enzyme activities. In the first experiment, pigs growing from 25 to 55 kg body weight were given two doses of pituitary porcine somatotropin (pST; 0 and 100 micrograms per kg body weight) and three levels of dietary energy (60, 80, and 100 % of free choice intake). In the second experiment, pigs growing from 30 to 60 kg body weight were given two doses of recombinant porcine somatotropin (rpST; 0 and 100 micrograms per kg body weight) and five levels of dietary crude protein (110, 150, 190, 230 and 270 g crude protein/kg diet). Liver and kidney arginase (ARG; EC 18.104.22.168) and liver aspartate aminotransferase (AAT; EC 22.214.171.124) activities were then determined in organ samples taken at slaughter time. Dietary energy did not change liver or kidney ARG. Activities of both ARG and AAT increased as dietary crude protein increased. Both pST and rpST decreased ARG, AAT and serum urea nitrogen. There was a lack of interaction between rpST therapy and dietary protein on either ARG or AAT activities, suggesting that set nutritional states are not required for expression of pST effects.