EFFECTS OF AN ENDOTOXIN CHALLENGE ON GROWTH-PERFORMANCE, CARCASS ACCRETION RATES, AND SERUM HORMONE AND METABOLITE CONCENTRATIONS IN CONTROL PIGS AND THOSE TREATED WITH RECOMBINANT PORCINE SOMATOTROPIN

Barrows were restrictively fed starting at 20 kg BW to determine the e ffects of endotoxin on growth performance of control and somatotropin- treated pigs. The following treatments were used: 1) daily i.m. vehicl e injection until 55 kg BW; 2) daily i.m. injections of 100 mu g of re combinant porcine somatotropin (pST)/kg BW, until 55 kg; 3) i.v. salin e injections for 7 d consecutively starting at 60 kg BW; 4) i.v. injec tions of 1 mu g of bacterial lipopolysaccharide (LPS)/kg BW for 7 d st arting at 60 kg BW; and 5) the combined LPS + pST treatment, with pST injections from 20 kg through the 7 d of LPS treatment. Pigs evaluated for LPS effects were fed to 60 kg anticipating a weight loss. Pigs we re bled at 0800 and 1100 at 55 kg and on d 7 of LPS treatment. Rectal temperatures were taken on d 7. Treatment with pST increased ADG by 13 to 20% and improved feed:gain by 17 to 23% before LPS treatment. Duri ng the 7 d of LPS injections, ADG and feed:gain did not differ, althou gh feed efficiency was impaired and variable. Rectal temperatures at 1 100 were progressively increased: control < LPS < LPS-pST (P < .01). P rotein accretion was improved 27% by pST treatment, and lipid accretio n was decreased 45% before LPS. Lipid stores decreased (P < .01) after LPS treatment in the pST-treated pigs. Lipopolysaccharide treatment a nd(or) decreased feed intake reduced the hyperinsulinemia and hypergly cemia (P < .01) associated with pST treatment. These results indicate that LPS induced a simulated septicemia and that the effects were not negated by pST treatment. The observed hyperthermia was additive, poss ibly due to increased lean body mass induced by pST combined with the pyrogenic effect of LPS.