Effects of decreasing phosphorus concentrations in diets and phytase supplementation on growth performance, stress response, and intestinal health in broiler chickens.

The current study aimed to investigate the effect of decreasing P concentrations in diets and phytase supplementation on growth performance, stress response, and intestinal health in broiler chickens. A total of four hundred 8-d-old Ross broiler chicks were randomly allotted to 1 of 4 dietary treatments with 10 replicates. Three treatment diets were formulated to contain different concentrations of available P (aP): adequate P (0.44 % aP), low P (0.30 % aP), and very low P (0.10 % aP) levels. One additional diet was prepared by supplementing 1,000 FTU/kg phytase in very low-P diets to maintain its aP concentrations equal to those in low-P diets. The experiment lasted for 25 d. It was observed that growth performance and toe ash concentrations were decreased (P < 0.05) in birds fed very low-P diets compared with those fed other treatment diets. Birds fed very low-P diets exhibited a greater (P < 0.05) blood heterophil:lymphocyte ratio than those fed other treatment diets. Jejunal villus height in birds fed adequate P diets or low-P diets was greater (P < 0.05) than those fed very low-P diets or very low-P diets with phytase. The malondialdehyde concentrations in the jejunal mucosa were greater (P < 0.05) for very low-P treatment than for other treatments. The expression levels of IL-4 and OCLN in the jejunal mucosa were less (P < 0.05) for adequate P treatment than for low-P treatment and very low-P with phytase treatment. Expression levels of P transporter genes in the jejunal mucosa were not affected by dietary treatments. In conclusion, feeding very low-P diets impaired growth performance, bone development, and jejunal morphology in broiler chickens with elevated stress response and intestinal lipid peroxidation. However, feeding low-P diets or very low-P diets with phytase maintained bone development, stress response, and antioxidant status in broiler chickens. The gene expression of intestinal P transporters were not influenced by decreasing P concentrations in diets and phytase supplementation in very low-P diets under the current experimental condition.