Effects of Dietary Aflatoxin on Performance and Zinc Metabolism in Dairy Calves

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Abstract
To examine the extent to which dietary Zn might alleviate aflatoxin toxicity, young dairy calves were fed diets containing 40 or 640 ppm Zn with 0 or 5 ppm alfatoxin for 3 wk. The aflatoxin mixture contained 80.5% [aflatoxin] B1, 19.5% G1 and less than 0.1% B2 and G2. The aflatoxin-fed calves exhibited characteristic signs of aflatoxicosis which included reduced feed intake, weight gains, nitrogen balance, pulse rate and respiration rate. Feed intake and weight gains recovered some during the 3rd wk. No gross abnormalities were observed in the liver or other organs at autopsy. Addition of 600 ppm Zn to diets containing aflatoxin did not alleviate the toxic conditions. Effects of aflatoxin or Zn metabolism were investigated during the 3rd wk of treatment through oral dosing of 65Zn. Absorption of 65Zn was slightly lower in aflatoxin-fed calves. The aflatoxin effect on absorption of 65Zn was less than that of high dietary Zn. Retention of 65Zn in small intestinal tissue was increased in aflatoxin-fed calves, but concentrations in other tissues were not affected. Stable Zn was reduced in liver and increased in kidney and 3 sections of the small intestine. Further research is needed to define more clearly the relationship of Zn to aflatoxin in dairy calves.