Copper (Cu) is essential for several copper-dependent enzymes, for example those involved in synthesis and maintenance of elastic connective tissue and mobilization of iron stores. About 25-40 per cent of the copper in a normal ration is absorbed in the intestines. Copper interacts with many other minerals including molybdenum, sulphur, zinc, selenium, cadmium and iron. Copper deficiency can lead to ostochondrosis, other developmental bone diseases and to anaemia.

Grass and hay contain 4-8 mg Cu per kg dry  matter and oats about the same. Good copper sources are most mineral supplements and compound feeds for horses. Copper requirement is about 10 mg per kg dry matter in ration.