Two experiments were conducted to compare a novel phytase with its commercial predecessor. In Exp. 1, Cobb 500 (n = 720) male broilers were weighed and fed one of 10 treatments from d 8 to 18 post-hatch. Treatments consisted of a nutrient adequate positive control ( PC ), a Ca and non-phytate P ( nPP ) deficient negative control ( NC ), the NC plus the novel phytase (phytase 1) at 187.5, 375, 750, 1,500 or 2,000 FYT/kg or the NC diet plus the commercially available phytase (phytase 2) at 500, 1,000 or 2,000 FYT/kg. In Exp. 2, Ross 308 (n = 1,008) male broilers were assigned to one of 7 treatments from d 1 to 36 post-hatch. The treatments consisted of a PC, a NC, the NC diet plus phytase 1 at 500, 1,000 or 2,000 FYT/kg or the NC diet plus phytase 2 at 1,000 or 2,000 FYT/kg. In both Exp. 1 and 2, birds fed the NC diet had reduced ( P < 0.05) weight gain ( WG ), feed intake ( FI ), or tibia ash compared with birds fed the PC. Phytase supplementation at >187.5 FYT/kg feed improved WG and FI in Exp. 1 and 2, whereas phytase 1 at 750 to 2,000 FYT/kg or phytase 2 at 2,000 FYT/kg was needed to improve tibia ash comparable to the PC in Exp. 1. Supplementing broiler diets with a novel phytase at a lower dose compared with the commercial phytase significantly increased ileal phytate degradation and P digestibility resulting in an increase in tibia ash. Tibia ash, ileal phytate P, and P digestibility are more sensitive, compared with growth performance, to detect differences between phytases at different dietary concentrations.

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