THE EFFECTS OF DIETARY SOYBEAN VERSUS SKIM MILK PROTEIN ON PLASMA ANDHEPATIC CONCENTRATIONS OF ZINC IN VEAL CALVES

We assessed the zinc status of veal calves that were fed milk replacer s containing either skim milk protein as the sole source of protein or a mixture of skim milk protein and soybean protein. After the milk re placers had been fed for 26 wk, mean body weight gain was 3 kg lower f or calves fed the skim milk plus soybean proteins; this decrease was n ot significant. Inclusion of dietary protein from soybeans versus milk protein alone reduced plasma concentrations of zinc by 43% and reduce d hepatic concentrations of zinc by 81%. The impairment of zinc status that was induced by the inclusion of soybean protein was probably cau sed by its phytate component. The effect of soybean protein on zinc st atus was rather specific because plasma and hepatic concentrations of copper were unaffected. Despite the high concentration of zinc (142 mg /kg of dry matter) in the milk replacer that contained milk plus soybe an proteins, calves displayed a shortage of zinc because their plasma and hepatic concentrations of zinc were significantly reduced.