Relationship between postnatal days, serum Cu concentration and plasma diamine oxidase activity in Japanese Black calves

The aim of study was to investigate the relationships among serum diamine oxidase (DAO) activity, postnatal days and the plasma copper (Cu) concentration, using calves with or without diarrhea. In healthy calves, the serum DAO activity was significantly higher at 2 postnatal days than at ≥7 postnatal days, and no significant changes were observed after 7 postnatal days. In addition, no significant correlation was found between serum DAO activity and plasma Cu concentration at all postnatal days in healthy calves. Although, the serum DAO activity in 14 diarrheic calves (66.78 ± 14.37 IU/ml) was lower than that in 19 healthy calves (170.33 ± 97.83 IU/ml, P