Evaluation of a novel hybrid 6-phytase using an updated phosphorus deficiency model in broiler chickens
One-day-old broiler chicks were used to investigate the optimal age to start feeding P-deficient diets with two non-phytate P (nPP) concentrations in exp. 1 and 7-d-old broiler chicks were used to determine P equivalency of a hybrid 6-phytase to inorganic P in monocalcium phosphate in exp. 2. In exp. 1, six treatments were prepared with 5, 6, or 7-d-old birds to start feeding P-deficient diets with 1.3 or 1.5 g kg-1 nPP. Age of birds to start feeding P-deficient diets tended to decrease (P = 0.052) mortality of birds during 14 days of feeding P-deficient diets. In exp. 2, twelve treatments including one basal diet, five diets supplied with 0.5, 0.9, 1.3, 1.7, or 2.1 g kg-1 inorganic P, and six diets supplied with 250, 500, 750, 1000, 1500, or 2000 FTU kg-1 phytase were fed to chickens from days 7 to 21 post hatching. Increasing phytase activity quadratically increased (P < 0.01) body weight gain, feed intake, and tibia ash of birds and apparent ileal digestibility and total tract retention of P. In conclusion, age of birds to start feeding PD diet affected their performance, and hybrid 6-phytase may partly replace monocalcium phosphate in P-deficient diet for broiler chickens.