Effects of dietary phosphorous supplementation on laying performance, egg quality, bone health and immune responses of laying hens challenged with Escherichia coli lipopolysaccharide

BACKGROUND: Phosphorus is an essential nutrient to maintain poultry health and performance. The objective of this study was to evaluate the effect of dietary phosphorus levels on egg production, egg quality, bone health, immune responses of laying hens challenged with Escherichia coli lipopolysaccharide. METHODS: Three hundred laying hens at 28 wk were randomly divided into 2 dietary treatments with 10 replicates of 15 birds. The wheat-soybean based diets contained either 0.12% or 0.4% non-phytate phosphorus (NPP). At 32 wk of age, all the birds of each dietary treatment were injected into the abdomen with 1.5 mg/kg body weight (BW) of either LPS or saline once a day at 24-h intervals for continuous 9 d. The performance of laying hens was evaluated for 9 d. The eggs after the fifth injection were collected to value the egg quality. Three hours after the first injection, blood was collected to measure serum metabolite and immune response associated parameters. Three hours after the fifth injection, the hens were euthanized to obtain tibia, cecal tonsils and jejunum. RESULTS: Compared with saline-injected hens, LPS-injected hens had lower feed intake and egg production (P < 0.05). Eggshell thickness, strength, albumin height and Haugh unit were significantly increased in LPS-injected hens compared with saline-injected hens (P < 0.05). Furthermore, laying hens challenged with LPS had lower villious height/ crypt depth ration than those received saline. Serum calcium, phosphorus and SOD activities significantly decreased in the LPS-injected hens compared with the control (P < 0.05). LPS up-regulated expression of IL-1β, IL-6 and IL-10 in cecum, and serum concentration of MDA, IL-1β and IL-6 (P < 0.05), whereas 0.40% dietary non-phytate phosphorus supplementation significantly increased (P < 0.05) villi height/crypt depth ratio, decreased (P < 0.05) serum MDA and IFN-γ concentration compared with the 0.12% non-phytate phosphorus group. CONCLUSION: In summary, this study demonstrates that 0.40% dietary non-phytate phosphorus supplementation significantly increased calcium and phosphorus levels of eggshell, increased villi height/crypt depth ratio, decreased serum MDA and IFN-γ concentration compared with the 0.12% non-phytate phosphorus groups. The results indicate that high level of dietary non-phytate phosphorus exerts a potential effect in alleviating systemic inflammation of LPS-challenged laying hens.