Five hundred andfour 1-day-old Cobb broiler chickens were randomly allotted to 18 treatmentsand fed a semi-purified basal diet (4 g/kg total phosphorus) supplemented with2 levels of supplemental P (0.5 or 1 g/kg) during 21 days to evaluate performanceand bone mineralization; to assess the relative bioavailability of P (RBP) inwheat meal (WM) and roasted (RS) or extruded soybean meal (ES), with or withoutphytase (0 or 750 ftu/kg diet), using dicalcium phosphate (DC) as standard;and to estimate phosphorus excretion. Weight gain (WG), feed intake (FI), feedto gain ratio (FG), and tibia ash weigh (AW) were assessed. For each source,the RBP was calculated by the slope ratio method, when tibia ash weight wasregressed on P ingested. Ingested and fecal P was determined to calculate Pintake, and P excretion and excretion rate. Phytase addition increased overallFI, WG, and FG ratio by 3.3, 2.6 and 0.8%, respectively, but differences werenot significant. Overall AW was increased by 10.8% after the enzyme inclusionin the diets. The relative bioavailability of phosphorus values of tested WM,RS, and ES were increased by 6.32, 64.32, 76.99%, respectively, in responseto supplementation of phytase in diets containing WM, RS, and ES, respectively.Phytase reduced P excretion by 12.7% and the excretion rate by 15.0%, regardlessof the phosphorus source or level.
