Care with copper
The classic signs of copper deficiency are not as common these days and most of the time we are aiming to achieve levels that optimise production.
Copper deficiency can contribute to reduced growth rates in young cattle, diarrhoea, bone defects, lightening of the coat colour with patches of grey around the eyes, anaemia and possibly reduced milk production and poor reproductive performance.
Young deer suffer reduced growth rates and adult deer develop a condition called ‘swayback' where they lose co-ordination of their hind end. Lambs can also suffer from swayback. Copper deficiency in sheep will also lead to weak bones, wool abnormalities and possibly reduced fertility.
Inadequate copper levels are usually due to interfering minerals in the soil/pasture and not low levels of copper in the diet. Minerals that reduce the absorption of copper are called antagonists.
The main antagonists are:
Zinc - Many farmers must treat with high levels of zinc over the facial eczema (FE) season to prevent disease. Severe outbreaks of FE in zinc treated animals have been linked to high copper levels. If copper levels are adequate, copper supplementation should stop while animals are being supplemented with zinc. It is important to check animal trace element levels in the autumn following zinc FE treatment.
Molybdenum - Pasture molybdenum levels increase in water-logged soils over winter.
Iron - During winter, the amount of soil, and hence iron, ingested by animals increases (it can be up to 10% of the diet if grazing short muddy pastures, if silage has a lot of soil contamination or if the water table is high).
Copper requirements are higher during the late winter/early spring due to the demands of the developing foetus and early lactation so autumn is a good time of the year to test trace element levels in the herd to see whether there is enough copper reserve to get them through.
Assessing copper status is not always as simple as reading the test result from the lab. In interpreting lab results, age/breed of animals, feeding, level of production, copper, molybdenum, sulphur and iron levels in the feed, clinical signs of deficiency and previous copper use are all important factors that your vet will consider when advising on copper supplementation.