Ruminants including cattle have capacity to utilize plant fiber as energy source. This unique capacity is attributed to the activity of rumen bacteria and the ability of animals to metabolize bacterial fermentation products. Interestingly, new-born ruminants, such as calves, do not possess this capacity. The function of digestive organs develops during the early stage of their lives to become herbivores. Our group mainly research the cellular and molecular mechanism of development of rumen epithelial tissue, and the associated alterations in immune and metabolic functions in growing cattle.