The Effects of Dietary Phosphorus on Productive Performance and Egg Quality of Ten Strains of White Leghorns

One thousand five hundred and thirty-six individually caged S.C.W.L. hens were fed corn, wheat, soybean diets formulated to contain 0.55, 0.50, 0.45 and 0.40% available or 0.47, 0.43, 0.38 and 0.33% inorganic phosphorus from 140 to 497 d. of age. The hens were from three commercial strains, three 2-way and three 3-way strain crosses and from a control strain. Egg quality measurements were taken on eggs laid over 5 d. intervals seven times during the experiment. Chemical analyses indicated that the diets fed contained 0.58, 0.55, 0.50 and 0.45% available and 0.48, 0.45, 0.42 and 0.38% inorganic phosphorus. Phosphorus level had no significant effect on feed intake or efficiency, egg production, sexual maturity, egg weight, blood spots or mortality but had a significant effect on 497 d. body weight and egg specific gravity at 165, 225, 277, 335, 390, 445 and 490 d.; however, the differences were small for this latter trait and probably of little practical importance. Strain of bird had a significant effect on all traits except mortality and blood spots. There were very few diet × strain interactions. The results indicate that a level of 0.45% available phosphorus is adequate for laying hens under practical conditions.