Copper deficiency in ruminants.

Copper deficiency can reduce the productivity of livestock. The effect of copper deficiency on a number of copper enzymes and copper-dependent systems is discussed, to highlight the areas where their role needs to be clarified. Special reference is made to cytochrome c oxidase, lysyl oxidase, superoxide dismutase and endoplasmic reticulum enzymes and to their role in the expression of disease. The modification of microbiological insult by a change in superoxide dismutase activity without any other direct metabolic consequences is discussed, to introduce the concept of an external challenge being necessary before any effect of an otherwise sub-clinical copper deficiency is observed. The changes in activity of the various copper enzymes are described in clinical and experimentally induced copper deficiency in sheep and cattle, two species in which copper deficiency can have economic consequences. The diagnostic value of various blood markers, such as copper, caeruloplasmin and erythrocyte superoxide dismutase is discussed. The measured degree of hypocupraemia is related to different types of sampling (e.g. plasma or serum), physiological status (e.g. in the pre- and postpartum cow), changes that occur in the neonate, and also to the effect of the acute-phase reaction. The use of erythrocyte superoxide dismutase as a marker for the copper status of sheep and cattle is compared with more conventional markers such as plasma concentration of copper. The use of blood markers to map the extent and location of hypocupraemia (due to reduced copper intake or availability) among suckler (beef) herds in Northern Ireland is also discussed.