The Effect of Added Magnesium on the Availability of Zinc with Some High-Protein Feedstuffs

IT HAS been noted that in a number of oil seed meals the magnesium content is equal to or greater than the calcium content (Lease and Williams, 1967). When zinc-containing extracts of these same meals were made (Lease, 1966), the magnesium followed the zinc through several purifications. Added calcium increases the chick’s dietary zinc requirement in isolated soy protein diets (O’Dell et al., 1958). The effect seems to be mediated through the intestinal tract, possibly through a greater uptake of zinc by phytate in the presence of calcium (Byrd and Matrone, 1965). Phytate occurs in nature as the calcium: magnesium salt of phytic acid. As a component of such a complex and as a companion Group II element, magnesium might be expected to act as does calcium in increasing zinc uptake in the presence of phytate. The effect of added magnesium on the chick’s dietary zinc requirements was determined. Five …