EFFECTS OF PHYTASE AND 1,25-DIHYDROXYCHOLECALCIFEROL ON PHYTATE UTILIZATION AND THE QUANTITATIVE REQUIREMENT FOR CALCIUM AND PHOSPHORUS IN YOUNG BROILER-CHICKENS

Three experiments were conducted to determine the effects of supplemen ting 1,25-dihydroxycholecalciferol [1,25-(OH)(2)D-3] and a commercial phytase product on Ca and P requirements of 0- to 21-d-old broiler mal es. These experiments were conducted with four levels of dietary Ca an d P in corn-soybean diets with and without supplementation of 5 mu g/k g of 1,25-(OH)(2)D-3, 600 units/kg of phytase, and the combination of these supplements. The results show that these levels of phytase and 1 ,25-(OH)(2)D-3 can replace up to 0.1% of the inorganic P for criteria such as BW, bone ash, and plasma P. Both supplements increased phytate P retention, whereas higher levels of Ca and P decreased phytate P re tention. The addition of 1,25-(OH)(2)D-3, but not phytase, reduced Ca requirements and decreased the incidence of tibial dyschondroplasia. T he combination of these levels of phytase and 1,25-(OH)(2)D-3 replaced 0.2% inorganic P for criteria such as BW, bone ash, and P rickets. To tal dietary P requirements are estimated to be between 0.55 and 0.60% at the levels of phytase and 1,25-(OH)(2)D-3, listed above, or 0.45% w hen the combination is added. The Ca requirements are estimated to be 0.77% when 1,25-(OH)(2)D-3 is added to the diet and 0.9 to 0.95% when phytase is added.