Overview of rumen epithelial cell differentiation and mitochondrial energy metabolism. A: Changes of rumen epithelial differentiation and mitochondrial energy metabolism. B: Scanning electron microscopy observation of epithelial cells. “M” represents mitochondrion, “N” represents nucleus. “*” represents P < .05, “**” represents P < .01; CON, nutritionally enriched group; LN, solid diet deficiency group received only milk. The data are presented as the mean ± SEM.