Lack of Effect of Dietary Factors on Nicarbazin Toxicity in Broiler Chicks

Effects of dietary fat, protein, and methionine levels and the type of dietary grain in nicarbazin-containing diets on the growth response of broiler chicks were evaluated in five experiments in a factorial design. Nicarbazin at levels ranging from 100 to 200 mg/kg significantly (P less than .05) depressed weight gain and feed efficiency. Feed intake was significantly reduced only when nicarbazin was used at levels of 150 and 200 mg/kg. The latter concentration also significantly decreased water intake and water:feed ratio. Nicarbazin, at a level of 150 mg/kg, did not affect dietary metabolizable energy content or the retention of nitrogen and dry matter. A higher level of soybean oil (3.5 vs. .5 or 1.0%) did not counteract the growth-depressing effects of 100, 150, and 200 mg nicarbazin/kg. The growth-depressing effect of the highest dose also was not affected by increasing the protein level from 18.2 to 20.4%. Neither type of dietary grains (corn vs. sorghum) nor supplemental methionine level affected the toxicity of 125 mg nicarbazin/kg. Water intake and water:feed ratio were significantly increased due to elevation of dietary protein and fat levels. It was concluded that the severity of the growth-depressing effect of nicarbazin on chicks was not dependent on the levels of dietary unsaturated fat, protein, and methionine.