Influence of dietary zinc or cadmium on hair and tissue mineral concentrations in rats and goats.

Three experiments were conducted to determine whether concentrations of minerals in hair and other tissues of rats and goats are affected by level of dietary Zn or Cd. In the first experiment, rats were fed diets that contained 10.3, 20.5, 33.7, 41.3 or 52.9 micrograms Zn/g for 57 d. Rats fed the diet that contained 10.3 micrograms Zn/g suffered from mild Zn deficiency, as indicated by depressed feed intakes and slower growth rates than rats fed diets containing higher amounts of Zn. Zinc concentrations in hair (P less than .01), liver (P less than .01) and kidney (P less than .01) increased as dietary Zn increased. Confidence intervals for dietary Zn concentration predicted from Zn analysis of hair were large. In the second experiment, rats were fed diets that contained .1, 4.0, 7.6, 10.1 or 15.9 micrograms Cd/g for 57 d. Total growth, feed intake, feed efficiency and liver, kidney and testes weights were not affected (P greater than .05) by dietary Cd concentration. Cadmium increased linearly in liver (P less than .01) and kidney (P less than .01) and quadratically in testes (P less than .01) as Cd intake increased, but Cd in hair was not affected by dietary level of Cd. High correlations between Cd concentrations in liver (R2 = .88) and kidney (R2 = .90) and dietary Cd concentration indicate that Cd intakes of rats may be accurately predicted from Cd analyses of these tissues. In the third experiment, goats were fed diets containing 0, 10.4, 18.0 or 28.5 micrograms Cd/g for 125 d. Growth, feed intake, feed efficiency and liver and kidney weights were not affected by dietary Cd intake. Cadmium in hair samples was not affected by level of dietary Cd; however, cadmium in liver (P less than .01), kidney (P less than .01) and proximal duodenum (P less than .01) increased as dietary Cd increased. Cadmium in liver, kidney, lungs and proximal duodenum was highly correlated (R2 = .67, .89, .57, .49, respectively) with dietary Cd concentration.