Studies on semduramicin and nutritional responses: 2. Methionine levels

Three experiments were conducted to determine whether feeding semduramicin at recommended levels would affect the broiler chicken's response to dietar y methionine. In Experiment 1, three levels of methionine (0, 0.15, 0.30%) were fed to chicks in battery brooders. In Experiment 2, two levels of prot ein (18 and 22%) and three levels of methionine (0, 0.15, 0.30%) were fed t o chicks in floor pens from 18 to 44 d. In Experiment 3, two methionine sup plements were fed during each of the starter (0 and 0.21%, 0 to 18 d) and g rower (0 and 0.10%, 18 to 35 d) periods to chicks in floor pens. In all exp eriments, male commercial broiler chicks were used, and all, diets were fed with and without 25 mg/kg diet of semduramicin. The basal diets were based on corn, soybean meal, and poultry oil. In Experiment 1, there was a growt h and feed conversion ratio response to methionine supplements, but there w as no effect of semduramicin on growth nor any semduramicin by methionine s upplement interaction. In Experiment 2, at 44 d, protein and methionine lev els both influenced feed conversion ratios, but semduramicin did not. Feedi ng 22 vs 18% protein increased carcass and breast muscle yields and decreas ed abdominal fat pad weights. The results of Experiments 2 and 3 were very similar. Overall, the effects of semduramicin on growth and processing para meters were small and not significant, but considerable benefits in perform ance and carcass parameters could be realized by feeding the higher levels of protein or methionine.