Effects of arsanilic acid and monensin when given simultaneously in the diet of broiler chicks.

Monensin, a monocarboxylic acid ionophore, is an effective anticoccidial agent in chickens. Arsanilic acid is a widely used growth promoter in chickens. A dietary interaction between these 2 compounds was studied. Male broiler (Hubbard) chicks were offered 1 of 8 experimental diets containing these 2 compounds from their tenth until 32nd day of age. These diets consisted of a base of 26.5% corn, 26.5% wheat, and 37.5% soybean meal and had an energy value of 12.98 mJ/kg. Monensin varied in concentration from 50 to 200 mg/kg and arsanilic acid varied in concentration from 0 to 500 mg/kg. Arsanilic acid was found to significantly alter the pattern of weight gain among birds. An interaction was observed to occur between monensin and arsanilic acid only in terms of final bird weights. Growth depression, normally associated with monensin supplementation, was alleviated by arsanilic acid addition. There were no differences among the 8 groups based on gross pathological and histological examination of the birds. Tissue arsenic concentrations were found to increase with increasing dose of arsanilic acid in the diet. No tissue monensin concentrations were detectable by the methodology used.