Reduced dietary phosphorus levels for layers

Two experiments were undertaken to study the response of White Leghorn hens to low dietary phosphorus levels from 18 to 64 wk of age. A corn-soybean meal diet containing .2% available phosphorus gave similar performance, up to 32 wk of age, as a similar control diet containing .4% available phosphorus. Beyond 32 wk, although shell quality and average egg weight were similar, egg production was significantly reduced with the lower phosphorus diet. Phosphorus excretion (grams per bird per day) averaged .47 g for .4% vs .28 g for .2% available phosphorus when measured at 28 wk of age. In a second experiment identical procedures and bird number as used in Experiment 1 were employed with the exception that the test diet contained .3% rather than .2% available phosphorus. No differences were noted for any of the production variables measured between the .4 and .3% available phosphorus diets. Phosphorus excretion data collected at 25, 32, 44, and 60 wk of age showed a decrease of approximately 20% for hens receiving the lower phosphorus diet. Indeed the overall average for phosphorus excretion for the lower phosphorus diet was calculated to be identical to the 20% lower total phosphorus content of this diet (.59 vs .47%).