Roxarsone toxicity in the chick as influenced by dietary cysteine and copper and by experimental infection with Eimeria acervulina.

A series of experiments was conducted with crossbred chicks to determine the effects of L-cysteine, copper, and coccidiosis on roxarsone toxicity. Levels of roxarsone in excess of 50 mg/kg depressed performance and increased kidney arsenic concentration. L-cysteine x HCl x H2O (59%) increased rate and efficiency of gain when added to the basal diet, but depressed performance, increased kidney arsenic concentration, and enhanced mortality when added to diets containing toxic levels of roxarsone (200 mg/kg or higher). Moreover, excess copper (500 mg/kg) partially alleviated the gain/feed depression due to the combination of cysteine and roxarsone. Cysteine, in fact, increased feed efficiency in birds fed excess copper in the absence of roxarsone. Eimeria acervulina infection (duodenal coccidiosis) depressed gain and feed efficiency. The depression in feed efficiency was more severe in the presence of roxarsone (50 or 300 mg/kg). In the absence of coccidiosis, 50 mg/kg roxarsone slightly increased gain/feed ratio.