ANTICOCCIDIAL EFFICACY OF SEMDURAMICIN .1. EVALUATION AGAINST FIELD ISOLATES BY DOSE TITRATION IN BATTERY TESTS

Semduramicin (AVIAX(TM)), a novel polyether ionophore, was titrated in a series of five battery tests at 20, 25, and 30 ppm in feed to deter mine the optimum level for use. Twelve-day-old broiler chicks were med icated for 48 h prior to inoculation in each 9-day test. The inocula i ncluded monospecific field isolates of Eimeria tenella, Eimeria brunet ti, Eimeria necatrix, and Eimeria maxima, and a mixture of these speci es with Eimeria acervulina and Eimeria mitis. The numbers of oocysts i noculated were selected after titration of each species and the mixtur e of species. All three concentrations of semduramicin significantly ( P < .05) reduced coccidiosis mortality and lesion scores and achieved lower feed:gain ratios and greater weight gains than the infected, unm edicated treatments. A concentration of 25 ppm semduramicin was determ ined to be optimal based on improved lesion control compared with 20 p pm and improved weight gain compared with 30 ppm.