Effect of dietary fat and protein levels on monensin toxicity in broiler chicks.

The effects of dietary fat level, fat source, and protein level on the growth response of broiler chicks were evaluated in two experiments with a factorial design. A higher level of soybean oil (SO) (3.5 vs. .5%) in diets containing either 18.2 or 20.4% protein significantly (P less than .05) counteracted the depressing effect of monensin on feed intake and weight gain in male chicks in the first experiment. Dietary protein level did not significantly (P greater than .05) affect the response to monensin, nor did monensin affect feed to gain ratio. The higher SO level of 3.5% in diets containing 18.2% protein reduced, at times significantly (P less than .05), the depressing effect of monensin on feed and water intake, water to feed ratio, weight gain, and the retention of dry matter and nitrogen in female chicks in the second experiment. A similar higher level of tallow resulted in less pronounced effects on most of the parameters. Monensin supplementation did not affect dietary metabolizable energy content, but significantly (P less than .01) increased feed to gain ratio and the percent of fecal dry matter. It was concluded that the toxicity of monensin to chicks might be alleviated by increasing dietary unsaturated fat and protein levels.