COMPARISON OF MICROBIAL PHYTASE AND INORGANIC-PHOSPHATE IN MALE CHICKENS - THE INFLUENCE ON PERFORMANCE DATA, MINERAL RETENTION AND DIETARY CALCIUM

In an experiment with broiler chickens, the effects of graded dietary supplements of microbial phytase from genetically modified Aspergillus niger (125, 250, 500 or 1500 U/kg) and of P from monocalciumphosphate (0.6, 1.2 or 1.8 g/kg) were tested in a P-deficient corn-soybean meal diet (3.5 g P/kg) at three Ca-levels (6, 7.5 or 9 g/kg). For each treatment, four replicates of 30 day-old male chickens housed in floorpens were used. Performance data and retentions of Ca and P were used as criteria after 14 and 40 days, respectively. Additions of phytase or inorganic P resulted in dose-dependent increases of live weight gain, feed consumption and retentions of Ca and P. Utilizations of P and phytate-P were significantlly improved by phytase. Inorganic P improved P-utilization after 14 days and reduced phytate-P-utilization after 14 and 40 days. Utilization of Ca was improved by phytase and by inorganic P. In phytase treatments, an increase in dietary Ca had significant negative effects on the utilizations of P, phytate-P and Ca. In treatments with inorganic P, the Ca-level only affected the utilization of Ca, and the utilizations of P and phytate-P after 14 days. Using live weight and P-retention as criteria, the P-equivalency of phytase at 6 g Ca/kg feed was calculated as 1 g P = 570 U and 1 g P = 1070 U at 14 days, and 1 g P = 850 U for both criteria at 40 days.