Use of erythrocyte copper:zinc superoxide dismutase activity and hair or fleece copper concentrations in the diagnosis of hypocuprosis in ruminants.

Changes in the activity of superoxide dismutase, a copper-containing enzyme in erythrocytes (ESOD), and changes in copper in hair or fleece were compared with the changes in plasma copper during copper depletion and repletion in steers, lambs and ewes. During depletion the decline in ESOD began later than the decline in plasma copper: the lag varied from 0 to 80 days in individual steers and it was least evident when young rapidly growing lambs were subjected to severe depletion. ESOD activity eventually declined at only one-third to one-seventh of the rate shown by plasma copper, the difference being particularly marked in severely depleted lambs. Repletion of ESOD began after repletion in plasma copper and continued more slowly particularly in growing animals. Hair and fleece copper also responded relatively slowly to depletion and repletion. Low values of ESOD and hair or fleece copper may have diagnostic significance, indicating a more prolonged or intense deficiency of copper and a higher probability of clinical and production responses to copper therapy than low plasma or liver copper values.