Effect of 3-nitro-4-hydroxyphenylarsonic acid on copper utilization by the pig, rat and chick.

Experiments were conducted to examine the effect of dietary roxarsone (3-nitro-4-hydroxyphenylarsonic acid) on Cu utilization by the pig, chick and rat. A fortified corn-soybean meal diet was fed in each experiment. Roxarsone dramatically reduced liver Cu concentration at all levels of supplemental Cu fed. The level of roxarsone commonly fed, 50 mg/kg diet, resulted in a two- to fourfold depression in liver Cu concentration in all species studied. The effects of roxarsone on weight gain were more perplexing. In the chick, the diets containing 100 and 250 mg Cu/kg depressed growth in the presence, but not in the absence, of 50 mg/kg dietary roxarsone. In contrast, at toxic levels of Cu, roxarsone had no effect on (500 or 750 mg Cu/kg diet) or slightly alleviated (1,000 mg Cu/kg diet) the growth-depressing effects of Cu. In the rat, a roxarsone level of 50 mg/kg diet exacerbated the growth-depressing effect of 1,000 mg Cu/kg diet. However, Cu had no effect on the growth depression that resulted from feeding a toxic level of roxarsone (250 mg/kg diet). The antagonizing effects of roxarsone and Cu on weight gain were not evident in the pig. Supplemental Cu (250 mg/kg diet) improved weight gain, but not feed efficiency, in starter pigs. Roxarsone (50 mg/kg diet) had no effect on the growth-promoting effects of Cu.