Abstract
It was examined how zinc (Zn) and copper (Cu) might affect the decomposition of phytate phosphorus (P) in corn and sorghum and soybean meal by phytase.
Phytase solution of pH 7 or pH 5, which was dissolved in 0.5M acetic acid buffer solution, was added to the test tube containing the solution of powdered feedstuffs and Zn or Cu. Incubating at 37°C for 1 hour, the rate of decomposition prevention of phytate P is obtained. The higher the concentration of Zn, Cu and pH are, the rate of decomposition prevention of phytate P became high. At the same pH levels, the rate of decomposition prevention of phytate P by Zn became high compared with Cu, especially at the concentration of 2mM or more. Comparing the three feedstuffs, the rate of decomposition of phytate P in them by Zn and Cu was low at soybean meal compared with corn and sorghum. In order to maximize activity of phytase in diet and to promote availability of phytate P, it may be important to reduce the excess addition of Zn and Cu to diet, which is usually done in commercial diets.
