Broiler nonphytin phosphorus requirement in the finisher and withdrawal phases of a commercial four-phase feeding system.

Two experiments were conducted to determine the nonphytin phosphorus (nPP) requirement for broilers, based on broken line analysis, in the finisher (32 to 42 d) and withdrawal phases (42 to 49 d) of a four-phase feeding program. The determined nPP concentrations used were 0.15, 0.19, 0.26, and 0.31% in the finisher phase, experiment 1 (Exp 1), and 0.10, 0.13, 0.22, and 0.27% in the withdrawal phase, experiment 2 (Exp 2). The analyzed calcium levels in the diets were 0.69 +/- 0.02% and 0.72 +/- 0.05% in Exp 1 and 2, respectively. In Exp 2, an additional treatment was included in which birds were fed NRC-recommended (1994) nPP levels from hatch to 49 d. There were no differences (P>0.05) among dietary treatments in weight gain, feed intake, and feed efficiency in either experiment. In Exp 1, tibia ash weight of birds fed the diets containing 0.15% nPP was lower (P<0.05) than that of birds fed diets containing 0.19, 0.26, or 0.31% nPP. A requirement of 0.20 +/- 0.01% nPP was determined for male broilers weighing between 1,541 to 2,194 g and from 32 to 42 d of age based on broken line analysis of tibia ash weight response to different dietary nPP levels. In Exp 2, the nPP requirement of male broilers weighing between 2,396 g at 42 d and 3,076 g at 49 d, based on tibia ash weight, was 0.16 +/- 0.02% nPP.