Influence of cage density and prior dietary phosphorus level on phosphorus requirement of commercial leghorns

Department of Poultry Science and Alabama Agriculture Experiment Station, Auburn University, 36849, USA.

Two studies were conducted to determine whether cage density and prior dietary nonphytate P (NPP) level affect hens' P requirements. In Experiment 1, hens were housed at three cage densities (300, 400, and 600 cm2 or 46.5, 62.0, and 93.0 inches2/hen) and fed four levels of NPP (0.15, 0.25, 0.35, and 0.40%) for 6 wk to determine the effect of cage density on the P requirement. Egg production (EP), feed consumption (FC), egg weight (EW), and egg specific gravity (ESG) were measured to evaluate performance. Cage density influenced EP within Week 1 (P < 0.01), and during Weeks 5 and 6, there was a cage density x NPP-level interaction (P < 0.05). At 300 cm2, EP was more severely affected by 0.15 and 0.25% NPP than at 400 and 600 cm2. A linear decrease (P < 0.001) in FC was observed because of decreased NPP. Hens at 300 cm2 consumed 4 g less feed/hen per d than hens at 400 cm2. A linear decrease in EW was observed as the NPP level decreased (P < 0.01) from 0.25 to 0.15%, and there was no effect of cage density. Experiment 2 was conducted to determine the effect of prior dietary P levels on time required to create a P deficiency. Hens fed 0.4% NPP were divided into two groups and fed 0.25 and 0.4% NPP for 4 wk. At the end of 4 wk, hens fed 0.25% NPP were further divided into three groups and were fed diets containing 0.09, 0.25, and 0.30% NPP for an additional 6 wk. Hens fed 0.4% NPP were divided into three groups and fed diets containing 0.09, 0.4, and 0.45% NPP. Reduction of NPP from 0.4 and 0.25% to 0.09% reduced EP by 8.5 and 6.8%, respectively, within 3 wk. Prior NPP levels had no influence on time required to create a P deficiency in terms of EP. Reduction of NPP from 0.4 and 0.25% to 0.09% reduced (P < 0.05) FC. A decline in FC occurred 2 wk earlier in hens previously fed 0.4% than those fed 0.25% NPP. This result indicates that hens fed 0.4% NPP became P deficient more quickly than hens fed 0.25%. We concluded that cage density and prior NPP level affect the hen P requirements or time required to create a P deficiency.

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