Effects of dietary phosphorus, phytase, and 25-hydroxycholecalciferol on performance of broiler chickens grown in floor pens.

Three 49-d experiments (Exp 1, 2, and 3) with broilers in floor pens were conducted to test the applicability of nonphytin phosphorus (NPP) requirements and the NPP-sparing effect of phytase (PHY) and 25-hydroxycholecalciferol (25D) determined previously in battery Exp. Six dietary NPP treatments were tested using a 4-phase feeding program. Treatments 1 to 6 were NRC (1994) NPP (C); University of Maryland (UMD) NPP; UMD NPP - 0.064% (UMD+PHY); UMD NPP - 0.09% (UMD+PHY+25D); NRC - 0.10% (C+PHY), and 90% UMD NPP (NC), respectively. Treatments 3, 4, and 5 had 600 U of PHY/kg of diet. Treatment 4 also had 70 microg of 25D/kg of diet; NPP concentrations were reduced to account for the sparing effect of these additives. No differences in hatch to 49 d BW were observed between treatments in Exp 1 and 2, and only in Exp 3 were the BW of the NC broilers (2.86 kg) different (P < 0.05) from those fed the C, UMD, and UMD+PHY treatments (2.96, 2.94, and 2.98 kg, respectively). Cumulative NPP consumption per bird was lowest (P < 0.05) for broilers fed the UMD+PHY+25D treatment (8.65 g in Exp 3) compared with those fed the C, NC, UMD, and UMD+PHY treatments (18.19, 10.60, 13.63, and 11.01 g, respectively for Exp 3). Application of any of these treatments reduced total P and NPP consumption compared with C. The results of this series of floor pen Exp validate the UMD NPP recommendations for a 4-phase feed program and the PHY and 25D NPP-sparing effects observed in battery trials without negatively affecting broiler performance.