The dietary treatments were s follows: (1) control (CON) ted a basal diet; (2) the basal diet plus antibiotic ( 40 mg chlortetrecycline per kg of diet, ANT); (3) the basal diet plus 0.1% ZnCP; (4) the basal det plus 0.2% ZnCP; (5) the basal diet plus 0.4% ZnCP.