Biochemical and pathological changes in tissues of Friesian cattle during the experimental induction of copper deficiency.

1. Copper deficiency was induced in five Friesian cattle offered a semi-synthetic diet containing less than 1 mgCu/kg. Changes in blood and liver Cu contents and in the Cu-containing enzymes, ferroxidase I (caeruloplasmin; EC 1.16.3.1) and monoamine oxidase (EC 1.4.3.4) of plasma and cytochrome oxidase (EC 1.9.3.1) of liver and skeletal muscle were monitored during Cu depletion. 2. Rapid decreases in blood and liver Cu and plasma ferroxidase I activity were found at least 80 d before the first appearance of overt clinical signs of deficiency. Plasma monoamine oxidase and liver cytochrome oxidase activities decreased less rapidly and thus may provide useful indices of chronic Cu depletion.