Response of Laying Hens to Diets Varying in Crude Protein or Available Phosphorus

Two experiments were conducted using Babcock B300, Dekalb Delta, H&N, and Shave White pullets. Chicks were grown to 18 wk of age under similar conditions and transferred to laying cages. In Experiment 1, pullets of each strain received diets at 16.8% crude protein or at 14.4% crude protein with supplemental methionine and lysine. In Experiment 2 pullets received diets containing either 0.42, 0.35, or 0.28% available phosphorus. Both experiments revealed very few significant strain x diet interactions. The only meaningful strain effects were related to feed intake and body weight. Feeding the lower-protein diet had few effects on performance, although there was an unexpected increase in albumen height. The three levels of diet phosphorus had no effect on any of the usual performance criteria. If strain-specific differences in nutrient requirements for layers exist outside of accommodation for variable feed intake, the effects will be quite small when diets are modified to reduce manure loading by either nitrogen or phosphorus.