Effects Of Daily Porcine SomatoTopin Administration On The Lysine Requirement Of Growing Pigs

Kansas State University Swine Reserach. One-hundred twenty crossbred barrows initially weighing 68.7 lb were used to determine the lysine requirement of growing pigs injected with 5 mg/d porcine somatotropin (pST) during a 5-wk growth trial. Pigs received one of six levels of dietary lysine (.7, 1.1, 1.5, 1.9, 2.3, or 2.7%) and were injected daily with either 5 mg pST or placebo. During the 5 wk trial, pST-injected pigs had increased average daily gain (ADG), decreased average daily feed intake (ADFI), and improved feed conversion (F/G) compared with placeboinjected pigs. With increasing dietary lysine, ADFI of pigs injected with both pST and placebo was reduced. Pigs injected with pST had improved ADG as dietary lysine increased to 1.5% and improved F/G as dietary lysine increased to 1.9%. Dietary lysine had no effect on ADG or F/G of placebo-injected pigs. Pigs injected with pST had improved average backfat, tenth rib fat depth, and longissimus area compared to placebo-injected pigs. Tenth rib fat depth of both placebo- and pST-injected pigs was reduced as dietary lysine increased. Longissimus area of pST-injected pigs improved as dietary lysine increased to 1.5%. The improvements in ADG, ADFI, F/G, and longissimus area of pST-injected pigs indicate that the dietary lysine requirement of growing pigs injected with 5 mg/d pST is 1.5 to 1.9%.