Abstract
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 bactericidal capacity of isolated neutrophils. Following initial experiments, four heifers from the copper-unsupplem-ented group were provided the copper-supplemented diet for 2 mo. Copper repletion improved neutrophil superoxide production and bactericidal capacity. Results suggest that mild copper deficiency may impair bovine neutrophil function. Further research is required to evaluate the effects of inflammation and infection on beneficial effects of copper supplementation.
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