Phosphorus requirement of commercial Leghorn pullets from 8 to 20 weeks

Hisex White pullets, hatched in November, were used to study the influence of the amount of dietary phosphorus in practical grower diets during the 8 to 20-week growing period. Measurement were made on 20-week body weight, bone ash, and layer house performance. All chicks were fed a 21% protein starter diet through 8 weeks at which time they were randomized into eight treatment groups. Grower diets were changed at 8, 12, and 16 weeks at which time different dietary phosphorus percents were used. Percents of total phosphorus used were .60, .55, .50, .45, and .32 for 8 to 12 weeks and .31 for 13 to 20 weeks. Lowering the phosphorus to .32% at 8 weeks or .31% at 12 weeks significantly reduced 20-week body weight. Lowering total phosphorus to .31% at 16 weeks did not significantly affect 20-week body weight. Bone ash measured at 20 weeks was not significantly affected by feeding less phosphorus. Laying house mortality, egg production, egg weight, and egg specific gravity were not influenced by lowering phosphorus in grower diets.