A S indicated in reviews by Taylor • (1965) and Nelson (1967) data are incomplete and often conflicting in regard to the influence of dietary factors on the extent to which chicks are able to utilize phytin phosphorus. Maddaiah et al. (1964) were unable to relate supplementation with dicalcium phosphate, or calcium or sodium phytates to intestinal phytase activity in the chick or the rat. Balance studies have shown (Pileggi et al., 19SS) that in the rat high dietary Ca lowered phytate hydrolysis; vitamin D 3 reversed this effect but the inorganic phosphorus liberated by the treatment was inadequate to prevent rickets. It has also been demonstrated that dietary vitamin D 3 increases the level of phytase activity in both chicks and rats (Steenbock et al., 1953, for chicks and rats, Pileggi et al., 1955, and Roberts et al., 1961, especially when rachitogenic rations were fed. On the other hand, Spitzer et al. (1948) reported that vitamin D had no effect on intestinal phytase in rats receiving slightly less than optimum phosphorus.The present paper contains observations on the properties of intestinal phytase in vitro which were employed in devising a quantitative assay procedure. The effects of dietary calcium, inorganic and phytate phosphorus and vitamin D 3 ori phytase and alkaline phosphatase of chick intestinal mucosa are presented. Data which suggest

Diets with varying levels of Ca, inorganic phosphorus (P1), and vitamin D3 were fed to chicks from 1 day of age. Alkaline phosphatase of intestinal mucosa was twofold higher at 3 weeks in female chicks fed 0.16% of P1 than in chicks fed 0.48% of P1 when the diets contained 7500 I.C.U. of vitamin D3 per kilogram and 1% of Ca. The effect of low dietary P1 was less pronounced when the diets contained 450 I.C.U. of vitamin D3 per kilogram and 1% of Ca but no definite pattern in enzyme activities due to level of P1 was observed with 0.53% of Ca. In male chicks there was a small but consistent increase (35–45%) in the activity of intestinal phosphatase when the diets were low in Ca, P1, or both. The level of vitamin D3 had no effect on the intestinal enzyme in male birds.