Mild Dietary Copper Insufficiency Depresses Blood Neutrophil Function in Dairy Cattle

Effects of dietary copper insufficiency on bovine blood neutrophil function were evaluated. Dairy heifers were maintained on a basal (6-7 mg Cu/kg diet) or copper-supplemented (20 mg Cu/kg diet) diet beginning 84 d prepartum. At approximately 35 d postpartum, heifers were bled for neutrophil isolation 1 d prior to and 2 d following intramammary infusion of endotoxin in 2 mammary quarters. Neutrophils were evaluated for in vitro production of superoxide anion, reduction of nitroblue tetrazolium, and bactericidal activity. Copper status did not affect neutrophil reduction of nitro-blue tetrazolium or production of superoxide anion. Neutrophil bacterial phagocytosis and number of bacteria ingested per neutrophil were similarly unaffected by diet. Prior to endotoxin infusion neutro-phils isolated from copper-supplemented heifers were significantly more effective at killing ingested bacteria than neutrophils from unsupplemented heifers. Endotoxin infusion eliminated diet-related differences in bacteri...