The Effects of Dietary Soybean Versus Skim Milk Protein on Plasma and Hepatic Concentrations of Zinc in Veal Calves

Abstract

We assessed the zinc status of veal calves that were fed milk replacers containing either skim milk protein as the sole source of protein or a mixture of skim milk protein and soybean protein. After the milk replacers had been fed for 26 wk, mean body weight gain was 3kg lower for calves fed the skim milk plus soybean proteins; this decrease was not significant. Inclusion of dietary protein from soybeans versus milk protein alone reduced plasma concentrations of zinc by 43% and reduced hepatic concentrations of zinc by 81%. The impairment of zinc status that was induced by the inclusion of soybean protein was probably caused by its phytate component. The effect of soybean protein on zinc status was rather specific because plasma and hepatic concentrations of copper were unaffected. Despite the high concentration of zinc (142mg/kg of dry matter) in the milk replacer that contained milk plus soybean proteins, calves displayed a shortage of zinc because their plasma and hepatic concentrations of zinc were significantly reduced.