THE nutritional interrelationships of calcium, phosphorus and magnesium have been the object of numerous scientific reports, many of which are contradictory. It is becoming evident, however, that the dietary requirement and physiological role of any one of these ions is influenced by the relative proportion of the others in the diet.Several authors have shown nutritional interrelationships among calcium, phosphorus and magnesium in rats (Forbes, 1963; and Toothill, 1963), in dogs (Bunce et al., 1963) and in guinea pigs (Morris and O’Dell, 1963). Alder (1927) and Buckner et al. (1932) reported better bone formation and egg production in laying hens when the magnesium content of the limestone added to the diet was low. Other reports (Tully and Franke, 1934; Branion, 1947; Supplee, 1963; Staller and Sunde, 1964; and Mehring and Johnson, (1965) indicated, however, that the addition of magnesium to the diet had no adverse effect on laying hens, and …