Phytase in starter and grower diets of White Pekin ducks

The growth performance and phosphorus utilization responses of ducks to phytase were investigated during the starter and grower phases. Five-hundred-seventy-six one-day-old drakes with an average initial BW of 55 g were grouped by BW into 8 blocks of 6 pens and assigned to 48 pens with 12 ducks per pen. The 6 dietary treatments consisted of: 1) positive control (PC), adequate in all nutrients with 4.5 g non-phytate phosphorus (nPP)/kg starter diet or 3.5 g nPP/kg grower diet; 2) negative control (NC), adequate in all other nutrients except phosphorus with 3.0 g nPP/kg starter diet or 2.0 g nPP/kg grower diet; 3) the NC plus phytase at 500 units/kg diet; 4) the NC plus phytase at 1,000 units/kg diet; 5) the NC plus phytase at 1,500 units/kg diet; and 6) the NC plus phytase at 15,000 units/kg diet. Starter and grower diets were fed from d 1 to 15 and d 15 to 43 post hatching, respectively. Ducks had free access to diets and water during the 42-day study. Feeding the low-P NC diet to ducks reduced (P < 0.01) gain and feed intake compared with the PC diet in both starter and grower phases. Supplementing the NC diet with phytase resulted in both linear and quadratic improvements (P < 0.05) in gain, feed intake, and G: F. Feeding the low-P NC diet to ducks reduced (P < 0.01) tibia ash compared with the PC diet. There were both linear and quadratic increases (P < 0.05) in tibia ash with phytase supplementation. Supplementing the NC diet with phytase resulted in both linear and quadratic increases (P < 0.001) in ileal digestibility and retention of P in both the starter and grower phases. The results of this study showed that phytase was efficacious in hydrolyzing phytate P for bone mineralization and growth of ducks through the starter and grower periods.