The influence of withdrawal time on the performance of broiler chickens fed semduramicin

Three 49-d experiments, with a total of 6,528 male broiler chicks in floor pens, were conducted to test the hypothesis that Semduramicin feeding-time affects the body weight gain, feed consumption, and feed conversion ratio of broilers. Semduramicin ionophore was added to corn and soybean meal-based diets at the recommended level, 25 mg/kg for 0,34,39, or 42 d. Thus, three withdrawal times were employed (7, 10, and 15 d) during each experiment. Significant differences among experiments were observed for body weight gain, feed intake, and feed conversion ratio, but no significant differences due to Semduramicin were noted in body weight or feed intake. There was only one treatment by experiment interaction found for 0-to-34-d feed intake (P = 0.028), but it was not evident for 0 to 39 d (P = 0.818) or any other times. Feeding Semduramicin with a 10- or 15-d withdrawal period resulted in an improvement in feed conversion of about 0.04 units.