Changes in serum concentration and activity of diamine oxidase during the first month of life in calves

The serum concentration and activity of diamine oxidase (DAO) in calves with or without diarrhea during the first month of life were examined. The serum DAO concentration was highest on day 0 after birth, and gradually decreased. No differences in serum DAO concentrations were observed between calves with diarrhea and control calves. In contrast, serum DAO activity was lowest on day 0 after birth, and gradually increased. Serum DAO activity in calves with diarrhea was lower than that in the control calves from day 20 after birth. These findings suggest that serum DAO activity and concentration are not correlated, and serum DAO activity is useful for assessing damage to the small intestinal mucosa in calves.