Effect of phytase, citric acid and calcium concentration on growth performance, carcass traits and bone chemical properties of broiler chicken fed diets containing low non-phytate phosphorus

Effect of different levels of calcium (0.3 and 0.6%), phytase (0 and 1500 FTU/kg), and citric acid (0 and 1%) in diets containing 0.15% of non-phytate phosphorus, on growth performance, carcass traits, and bone chemical properties were investigated using 882 10-day-old male broilers from 11 to 40 days of age in 2×2×2 factorial arrangements based on a completely randomized design including 9 treatments (positive control and eight diets without any inorganic phosphorus) and 7 replications. The supplementation of phytase increased average daily gain and gain to feed ratio, but the effect of phytase was more apparent in broiler chickens received diets containing 0.6% calcium at 25 to 40 days of age (P< 0.01). Reducing dietary calcium levels decreased average daily gain (11 to 24 days) and gain to feed ratio (11 to 24 and 25 to 42 days). Also, the inclusion of citric acid in diets containing 0.3% calcium had a negative effect on these traits (P< 0.01). The combination of phytase and citric acid in diets containing 0.6% Ca increased the feed efficiency compared to the 0.3% diet (P< 0.01). Phytase supplementation increased toe ash and bone sodium percentage and decreased bone calcium and phosphorus concentration (P< 0.01). Bone phosphorus decreased by reducing dietary calcium levels and phytase supplementation (P < 0.01). The relative heart and pancreas weight decreased with phytase supplementation (P< 0.05). Reducing dietary calcium levels increased the relative liver and pancreas weight and decreased abdominal fat and heart percentage (P< 0.05). According to the results, the combination of phytase and citric acid in diets containing 0.6% calcium was more effective in improving growth performance of broilers fed diets containing low non-phytate phosphorus.