Effect of roxarsone and bacitracin methylene disalicylate on the development of immunity to Eimeria in broilers given a live coccidiosis vaccine.

No significant differences in the BW, feed intake, feed conversion, or mortality of broilers that had been vaccinated at 3 d of age with a live coccidiosis vaccine were observed irrespective of whether they had been given roxarsone, bacitracin methylene disalicylate, or both drugs in the feed. The weight gain of birds challenged with a high dose of the vaccine at 51 d was not significantly different from that of unchallenged birds and no lesions of Eimeria species were found in their intestines irrespective of the medication given. It is concluded that roxarsone and bacitracin methylene disalicylate do not interfere with the acquisition of immunity to Eimeria species in broilers.