UTILIZATION OF PHYTATE PHOSPHORUS AND CALCIUM AS INFLUENCED BY MICROBIAL PHYTASE, CHOLECALCIFEROL, AND THE CALCIUM TOTAL PHOSPHORUS RATIO IN BROILER DIETS/

The present study was performed to evaluate the potential of microbial phytase and cholecalciferol (D-3) for improving the utilization of ph ytate P and Ca and the influence of the Ca:total (t) P ratio in a corn -soybean meal diet fed to broilers from hatch to 21 d of age. A 4 x 4 x 2 factorial arrangement of treatments was used: 1.1, 1.4, 1.7, and 2 .0:1 Ca:tP ratio; 0, 300, 600, and 900 U of phytase/kg of diet; and 66 and 660 mu g of D-3/kg of diet. Another four treatments were included : the four Ca:tP ratios with 6,600 mu g of D-3 addition, but without p hytase. Added phytase linearly increased (P < 0.001) BW gain, feed int ake, toe ash content, and P and Ca retention; these measurements were negatively influenced by widening the dietary Ca:tP ratio, and synerge tically improved by addition of D-3. Increasing the Ca:tP ratio decrea sed (P < 0.001) all measurements in the presence or absence of supplem ental phytase and D-3 Dietary Ca:tP ratios between 1.1:1 to 1.4:1 appe ars critical to the efficient use of supplemental phytase and D-3 for improving the utilization of phytate P and Ca. The addition of D-3 in corn-soybean meal diets indicated a potential for improving the utiliz ation of phytate P and Ca by increasing Ca and P retention by about 5 to 12% in birds, which led to an increase in toe ash content (P < 0.03 ). The enhanced phytate P utilization (P < 0.001) was also observed du ring assay of the phytase activity in the mixed diets with an addition of Dg and without added phytase in summary, the findings of this stud y suggested that phytase, D-3, and Ca:tP are important factors in degr ading phytate and improving phytate P and Ca utilization in broilers.