If the nutritional digestibility was too low, the body would suffer from malnutrition, and it would affect the biosynthesis of oxidase and the level of endogenous antioxidant, so as to increase the production of free radicals, the DNA content of intestinal cells, the protein synthesis, and cell proliferation, while could activate the autophagy pathway and promote apoptosis (Zhu et al., 2011), thus affected the expression of Bcl‐2/Bax, Bcl‐xl, p53, and other apoptosis genes. Here, BAX is linked to malnutrition.