Effects of dietary calcium, non-phytate phosphorus and electrolyte balance on the serum biochemical parameters and nutrient metabolism of yellow-feathered broilers fed a low-protein diet

This study was conducted to investigate the effects of calcium (Ca), non-phytate phosphorus (NPP), and electrolyte balance in a low-protein diet on the serum biochemical parameters, tibial Ca and phosphorus (P) deposition, and metabolizability of nutrients in yellow-feathered broilers aged 1 to 30 d. A 3 × 3 factorial completely randomized design was employed, including 3 levels of dietary Ca and NPP (0.70% and 0.35%, 0.80% and 0.40%, as well as 0.90% and 0.45%) and 3 levels of dietary electrolyte balance (DEB) (200, 250 and 300 mEq/kg), respectively. Dietary crude protein (CP) level was maintained at about 19%. A total of 324 1-d-old Spotted-brown male broilers, one of the breeds of yellow-feathered broilers, were randomly assigned to one of 9 treatments with 6 replicate cages per treatment and 6 birds per cage (length 100 cm × width 50 cm × height 45 cm). The birds were fed with the experimental diets for 30 d. Data were analyzed by 2-way ANOVA using the GLM procedure of SAS. The interaction between dietary Ca-NPP and DEB did affect (P < 0.05) the serum alanine aminotransferase activity, total protein and urea nitrogen, total tibial Ca and P deposition, and fecal P content, as well as the apparent metabolizability of CP and P. The change of dietary Ca and NPP from 0.70% and 0.35% to 0.90% and 0.45% increased (P < 0.05) fecal Ca by about 50%, and reduced (P < 0.05) apparent metabolizability of Ca by 13.7%. The variation of dietary Ca and NPP from 0.80% and 0.40% to 0.90% and 0.45% increased (P < 0.05) fecal N contents by 3.4%. In addition, increasing DEB from 200 to 250 or 300 mEq/kg increased (P < 0.05) serum aspartate aminotransferase activity, albumin, total cholesterol and triglycerides by 11.4% to 38.0%, and improved (P < 0.05) apparent dry matter metabolizability by 3.0% to 5.0%. These findings suggest that the balance among Ca, NPP, and DEB in low-protein diets plays a critical role in nutrient metabolism of broilers. A low-protein (19% CP) diet containing 0.80% Ca, 0.40% NPP, and 300 mEq/kg DEB appears to be optimal for the serum biochemical profile and nutrient utilization of yellow-feathered broilers aged 1 to 30 d.