Effects of Crude Protein and Phytase in the Diet on Growth Performance and Excretion Contents of Nitrogen and Phosphorus in Broiler Chicks

This study was conducted to investigate the appropriate levels of crude protein (CP) and phytase in the diet of broiler chicks in order to reduce nitrogen and phosphorus contents in feces while maintaining performance of broilers. Six hundred forty-eight 1-day-old male broilers (41.9±0.91 g) had a total of 3 × 3 complex factor of 3 levels of CP (22%, 21%, 20%) and 3 levels of phytase (1,000, 800, 500 FTU/kg) in the diet. Divided into 9 treatments, 4 replications per treatment, 18 birds per replication, were completely randomly assigned and reared in a metabolic cage for 7 days. Seven-day-old body weight (BW) and body weight gain (BWG) of broilers were significantly lower at CP 20% treatment ( P <0.05), and feed conversion ratio (FCR) was significantly lower at CP 21% and phytase 800 FTU/kg treatment ( P <0.05). Nitrogen and phosphorus contents in chicken excreta were significantly lower in CP 20% and phytase 500 FTU/kg treatment, respectively ( P <0.05). Interactions between CP and phytase in the feed were shown for nitrogen and phosphorus in feces ( P <0.05). In conclusion, considering the broiler performance and excretion contents of nitrogen and phosphorus, it is thought that CP and phytase levels of broiler chicks diet can be reduced by 21% and 800 FTU/kg, respectively.