Serum concentrations of copper, iron, and zinc during Escherichia coli-induced mastitis

Six Holstein cows were intracisternally challenged with 50 cfu of Escherichia coli to induce acute mastitis. Clinical status, milk concentrations of bacteria, and serum albumin concentration were determined to monitor the progress and severity of infection for 72 h after bacterial challenge. Blood samples were also collected throughout infection to determine serum concentrations of Zn, Fe, and Cu. Experimental E. coli mastitis resulted in mean serum concentrations of Zn, Fe, and Cu of 28, 35, and 52% of prechallenge concentrations. These decreases first occurred 4 to 12 h after peak bacterial concentration in milk. Changes in serum trace elements may occur too late in the pathogenesis of infection to decrease peak bacterial numbers in milk. However, mediation of infection and inflammation may occur in later stages of the infection process.