Influence of different phosphorus phase-feeding programs and dietary calcium level on performance and body phosphorus...

Two nonphytate P (NPP) feeding programs (.35, -.25, -.15% NPP or .45, -.35, -.25% NPP during the age intervals of 23 to 35, 35 to 51, and 51 to 71 wk, respectively) were evaluated for White Leghorn hens in a complete factorial arrangement with 3.3 or 4.0% dietary Ca. Total P (TP) concentrations of the NPP feeding programs, as determined by analysis, were .60, -.48, and -.37 or .70, -.58, and -.46%, respectively. Egg production, feed efficiency, and egg weight over the 48-wk experiment were reduced significantly by the .35, -.25, and -.15% NPP program, irrespective of dietary Ca. Most adverse effects of the low NPP program occurred from 51 to 71 wk when hens fed .15% NPP consumed about 150 mg NPP daily as compared with NPP intake of 250 mg daily for hens fed .25% NPP. Hens fed 3.3% Ca consumed significantly more feed than did those fed 4.0% Ca, irrespective of NPP feeding program or age period. Neither NPP or Ca levels affected eggshell thickness at 71 wk nor mortality during the experiment. Dietary NPP and Ca did not significantly affect P content of the body, including feathers. Body P declined from an average of 8.6 g/hen at 23 wk of age to 7.3 g/hen at 55 and 63 wk. By 71 wk, body P returned to 8.6 g/hen. The results show that NPP intakes of 250 mg and 150 mg/hen daily from 35 to 51 and from 51 to 71 wk, respectively, were inadequate for laying hens' performance, but no adverse effects of these NPP intakes on body P were detected. It seems that utilization of dietary P was affected adversely by high ambient temperatures.