Experiments were conducted with crossbred male chicks to evaluate the interactions among
roxarsone (50 mg/kg),
monensin (121 mg/kg), and
copper sulfate (100 mg/kg) as treatments for experimental Eimeria tenella and E. acervulina
infections. When diets containing
monensin,
roxarsone, or a combination of both were offered to chicks for 15 min or 1, 3, 5, or 8 days prior to E. tenella challenge (5 X 10(4) sporulated oocysts),
monensin fed for 15 min or
roxarsone fed for 1 day prior to challenge prevented morbidity. A
mixed infection of E. tenella and E. acervulina (5 X 10(4) and 4 X 10(5) sporulated oocysts, respectively) reduced gain and gain:feed conversion ratios and caused severe duodenal and cecal lesions at Day 6 of the experiment. Infected chicks gained faster when diets were supplemented with either
monensin or
roxarsone, but
monensin produced a larger response than
roxarsone. The
mixed infection decreased shank pigmentation, with amelioration activity evident from
monensin but not from
roxarsone. Lesion scores at Day 6 indicated markedly reduced lesions in the duodenum due to
monensin but not due to
roxarsone; likewise, reductions in cecal lesions occurred in birds fed
roxarsone but less so in birds fed
monensin. Lesion scores showed little evidence of additivity due to
monensin and
roxarsone. In general,
copper sulfate exerted no independent or interactive effect on any of the parameters evaluated. In a subsequent experiment, the effect of feeding
roxarsone in combination with the
biological reducing agent,
cysteine, was evaluated in E. tenella-infected chicks. Rate and efficiency of gain were improved and lesion scores were reduced by supplementary
roxarsone.(ABSTRACT TRUNCATED AT 250 WORDS)