found that ALP activity of pigs fed basal diet (containing 33 mg of Zn/kg) supplemented with 10, 25, 40, 60, or 80 mg/kg of zinc as sulfate increased linearly with zinc intake with a peak when dietary zinc reached 86 mg/kg. Dietary Zn might indirectly promote the growth of piglets by enhancing ALP activity. In this study, the activity of ALP was increased in serum of pigs treated with different Zn sources.