Copper is stored in the liver. These levels deplete over winter and are lowest in winter and spring, when iron and molybdenum are highest. When animals are grazing low they pick up more iron from the soil and this interferes with copper absorption. The availability of copper from pasture is dependent on molybdenum, selenium, iron, and zinc concentration in the diet. The requirement for copper is highest in young rapidly growing animals, in late pregnancy and early lactation. Calves are usually born with good liver reserves. Clinical signs of copper deficiency may not be specific particularly if deficiency is marginal. It can cause poor growth, diarrhoea, fading coat, bone fragility and reduced fertility. Copper is best assessed from liver samples but blood is useful at time of deficiency. Liver biopsies can be taken from your animals on your farm by your vet or from dead animals at the meat works. Check them in early winter to ensure adequate levels during late pregnancy and early lactation. Pasture can be analysed for copper as well as molybdenum, iron and selenium. Copper can be supplemented to animals either by injections or an oral form can be used. Ask your local vet for advice.