| One hundred and forty-four finishing pigs (initial weight = 57 kg) were utilized in two experiments to determine the effects of porcine somatotropin (pST) and dietary lysine on growth performance, carcass characteristics, and bone mechanical properties. In Experiment 1, pigs were injected daily in the with 4 mg pST and fed diets containing.6,.8, 1.9, 1.2, and 1.4% lysine. Control pigs (placebo injection) were fed the.6% lysine diet. Increasing dietary lysine level improved gain, feed conversion, and carcass traits without adversely affecting pork quality. In Experiment 2, pigs were injected daily with either 4 or 8 mg pST and fed diets containing.8, 1.0, 1.2, and 1.4% lysine. Control pigs were fed the.8% lysine diet. Increasing lysine level resulted in improved gain, feed conversion, and carcass traits. Increasing pST dosage also improved growth performance and carcass traits in a dose-dependent fashion. However, pigs injected with 8 mg/d pST required greater dietary lysine to maximize performance than those injected with 4 mg/d. In both experiments, bone ash and strength were decreased as growth rate increased from pST and lysine administration. However, bone wall thickness was stimulated by pST and dietary lysine. These data indicate that pST administration increases the lysine requirement of finishing pigs, and this increase is proportional to the quantity of pST administered. Growth performance and carcass traits were maximized in pigs injected with 4 mg/d pST with lysine intakes of 27 to 32 g/d, while pigs injected with 8 mg/d pST require at least 36 g/d to maximize performance. |
