Effects of different concentrations of AFB1 on the mRNA expression of apoptosis-related genes including (A) BCL2, (B) Bax, (C) TP53, and (D) the Bax/BCL2 ratio in canine small intestinal epithelial primary cells. Data are presented as the mean ± SEM (n = 4). Different letters (a, b, and c) above the bars indicate significant differences between means. ab indicates insignificant difference. Additionally, if the ANOVA was not statistically significant, no letter is displayed on the graph. AFB1, aflatoxin B1; CON, control; BCL2, B cell leukemia protein; Bax, BCL2-associated protein; TP53, tumor protein 53.