Phosphorous requirements of laying hens in a semiarid continental climate.

Single Comb White Leghorn layers raised in floor pens in conventional open housing were used to determine their phosphorous requirement in a semiarid continental climate. Dietary available phosphorous (AP) of .15, .25, .35, and .45% were fed continuously from 26 to 74 weeks of age. Concurrently, diets containing .45, .35, and .25% AP or .35, .25, and .15% AP were "phase fed" during the age intervals of 26 to 42, 42 to 54, and 54 to 74 weeks, respectively. Diets used were corn-soybean diets in which the phosphorous was varied by changing the level of dicalcium phosphate in the ration. Under the conditions of this experiment, hens required a minimum of .25% AP for best egg production, feed consumption, and body weight gain. The AP levels above .35% depressed shell thickness. In a phase-feeding program, when the last phase corresponds with the summer season, AP should not go below .25% for best performance.