Effect of copper source on phytase stability in the premix of weanling piglets

Abstract

An in vitro experiment was conducted to investigate the effect of tribasic copper (Cu) chloride [TBCC, Cu2(OH)3Cl] on phytase stability in the premix of weanling piglets at different temperatures in comparison with Cu sulfate. The 225-kg 1% premixes were supplemented with phytase at 50 000 PU/kg and divided into three parts of 75 kg each. One part was supplemented with 6 mg Cu/kg as Cu sulfate (the control), and the other two parts were supplemented with 250 mg Cu/kg either as TBCC or as Cu sulfate. Either 6 or 250 mg Cu/kg is based on the complete diet of weanling piglets. The three premixes were stored at room temperature (20−25°C), natural high temperature (28−36°C), or artificial high temperature (38 ± 2°C) for 0, 10, 20, 30, or 40 days. Copper source, storage temperature and duration of storage, the interaction between Cu source and duration of storage, and the interaction between temperature and duration of storage affected (P < 0.01) phytase activities in the 1% premixes. Phytase activities in the premixes supplemented with TBCC were significantly higher (P < 0.001) than those in the premixes supplemented with CuSO4 at 10 or 20 days of storage. Phytase activities in premixes decreased (P < 0.001) exponentially with duration of storage regardless of Cu source or storage temperature. When the premixes were stored at different duration of storage, phytase activities in the premixes decreased (P < 0.001) linearly as temperature increased. The results from this study indicate that TBCC could maintain the stability of phytase in the piglet premix much more effectively than Cu sulfate regardless of temperature and storage duration.