Mice were randomly assigned to one of the four groups (the GM corn group group, the parental corn group, the negative control and the positive control group) with 10 mice per group based on body weight. Mice in the GM corn group and the parental corn group were fed with a diet containing of 70% corresponding corn, which was designed to achieve the highest concentration of Bt protein in the GM corn group as much as possible. Another two groups of mice fed with AIN93G diet were set as the negative control and the positive control (intraperitoneal injection with saline or 200 mg/kg bw of CY by 24 h before the termination of the study, respectively) (as shown in Table 2). Diets were adjusted to confirm the same amount of macronutrients in all groups and thereby avoid effects caused by compositional differences among the diets. The main nutrient compositions of diets were analyzed by Pony Testing International Group (Beijing, China) (Table 3). Mice were housed by group with ad libitum access to water and corresponding diets for 30 days.