초록
An 8 week feeding trial was conducted with 864 ISA Brown laying hens, 48 weeks old, to determine if microbial phytase $(Natuphos^{(R)})$ supplementation can reduce non-phytate phosphorus (NPP) level in laying diets. The experiment consisted of four dietary treatments: T1, control diet with 0.26% NPP (0.55% total P) wand no supplementary phytase; T2, 0.21% NPP (0.50% total P) diet with 250 U of phytase/kg of diet; T3, 0.16% NPP (0.45% total P) diet with 250 U of phytase/kg of diet; and T4, 0.11% NPP (0.40% total P) diet with 250 U of phytase/kg of diet. T3 showed the highest egg production and egg weight and the lowest feed conversion while T4 gave the lowest egg production and the highest feed conversion and mortality. Daily feed consumption ranged from 130.4 g (T4) to 132.7 g (T2). T1 and T2 were not significantly different in the production parameters. Eggshell strength, egg specific gravity, and eggshell thickness were not significantly different among treatments. However, broken egg ratio was significantly lower in T2 and T4 than in T1. Retentions of Ca, P, Mg, and Cu were greater in phytase supplemented treatments (T2, T3, and T4) than the control (T1), and those in T3 and T4 were greater than in T2. Excretions of P in phytase supplemented treatments (T2, T3, and T4) were significantly (p<0.05) smaller than in T1 but excretions of N were not significantly different among the treatments. Contents of ash in tibiae were not significantly affected by treatments, but contents of Ca, P, Mg, and Zn was increased and that of Cu decreased by phytase supplementation. It is concluded that the NPP concentration in the diet of Brown layers consuming about 130 g/d of feed can be safely lowered from 0.26% (0.55% total P) to 0.16% (0.45% total P). The excretion of P was reduced by the inclusion of 250 U phytase/kg of diet.