Immune functions in broiler chicks as influenced by dietary phosphorus and vitamin D

The objectives were (i) to determine dietary phosphorus requirements for immune functions in broiler chicks and (ii) to investigate the effects of a vitamin D deficiency on immune system functions.;In the phosphorus studies, female broiler chicks were fed diets having.14,.19,.25,.30,.36,.47% non-phytate phosphorus (NPP) in experiment (Expt) 1,.25,.35,.45% NPP in Expt 2, and in Expt 3,.35 and.45% NPP levels. Dietary calcium was maintained at 1%.;Responses in weight gain, feed intake and feed:gain ratio plateaued at.35% NPP. Weight gain and feed:gain ratio at.35% and.45% NPP were essentially the same. Bone ash increased up to.47% NPP. Cutaneous basophil hypersensitivity (CBH) response against Phytohemagglutinin-P (PHA-P) was significantly better for chicks fed.45% NPP than.35% NPP diet. Primary antibody (Ab) titers to sheep erythrocytes (SE) increased substantially as the NPP level increased from.14 to.35% but no further improvement was observed at.47% NPP. Macrophage (MO phagocytic activity increased linearly as dietary level of NPP increased from.14 to.19% and did not improve by higher dietary levels of NPP. The ability of bone marrow cells to proliferate into colonies was numerically higher at.35% NPP than at.25%. Serum phosphorus increased linearly and serum Ca decreased as dietary NPP increased. In conclusion, less NPP is required for adequate Ab production, MO phagocytic function and bone marrow cell proliferation than for maximum bone ash. However CBH response was greatest at the same level of NPP as required for high bone mineralization.;In the three vitamin D studies, treatments consisted of vitamin D deficient (D...