Abstract: As an anti-nutrient, phytic acid was widely presented in plant feed materials, and it was often complexed with Cu²⁺, Zn²⁺, Fe²⁺, Ca²⁺, Mg²⁺ and other ions to reduce the bioavailability of mineral elements in livestock and poultry. Phytase could effectively degrade phytic acid, thereby releasing the complexed metal elements, thus improving the utilization of Cu, Zn, etc., and reducing the excretion. The purpose of this experiment was to determine the effect of phytase supplementation on the production performance of broilers and the emission of Cu, Zn and other elements in broiler chickens under reduced dietary Cu levels. A total of 480 healthy one-day-old broilers were randomly divided into 3 groups with 8 replicates in each group. The control group was fed a standard diet (8 mg·kg^-1 Cu without phytase), and the dietary Cu levels of the two experimental groups were 4 mg·kg^-1(50% Cu) and 0 mg·kg^-1 (0% Cu), and 1 200 U·kg^-1 phytase was supplemented to the diets, respectively. The production performance of broilers and the content of Cu, Zn and other elements in blood and bones were determined. Metabolic tests were carried out at 4 and 7 weeks to determine the apparent utilization of Cu and Zn and their excretion in feces. The results showed that phytase supplementation had no significant effect on the production performance of broilers at all stages when the dietary copper level was reduced (P>0.05), but had a promoting effect on the 21 d broiler tibia index (P=0.07), and the Mn content of the tibia in 0% Cu group was significantly higher than that in the CON group (P<0.05) at 21 d. In the 4th week, the apparent bioavailability of Ca, P, Cu, Zn, and Mn in the two Cu decreasing groups were significantly increased (P<0.05), and the apparent metabolic rates of Cu, Ca, and P increased in a dose-dependent manner. At the 7th week, the apparent metabolic rates of Cu and Zn in the 50% Cu group were significantly higher than those in the CON group (P<0.05). Compared with the CON group, the excretion of Cu, Zn and Mn in 0% Cu and 50% Cu groups were significantly decreased at the 4th week (P<0.05), and the excretion of Cu at the 7th week was significantly decreased (P<0.05). In conclusion, the supplementation of 1 200 U·kg^-1 phytase in the diet had no obvious effect on the production performance of broilers when the diet Cu level was reduced to 50% or 0% of the standard, but it could increase the apparent utilization rate of dietary Cu, Zn and reduce the excretion of fecal Cu and Zn.

Key words: broiler, phytase, copper, zinc, production performance, excretion