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 Totally Vets will consider when advising on copper supplementation.
How does copper deficiency affect an animal?
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 coordination 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.
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.
What causes copper deficiency?
The reason for inadequate copper levels is usually due to interfering minerals in the soil/pasture and not low levels of copper in the diet per se. Minerals that reduce the absorption of copper are called antagonists. The main antagonists are molybdenum, sulphur, iron and zinc. Antagonists have a large influence on the amount of copper that must be present in the diet to maintain optimal levels.
Is copper supplementation needed when treating for facial eczema?
At high levels zinc is a copper antagonist. 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. Fortunately copper requirements are generally not that high during the FE season. Though copper depletion is common during the FE season, it has not yet been linked to a reduction in animal performance. It is important to check animal trace element levels in the autumn following zinc FE treatment.
Why do copper levels fall over the winter?
Copper levels tend to fall over the winter and are often at their lowest heading into the spring. The reasons for this are:
- Pasture molybdenum levels increase in water-logged soils
- During the 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
Autumn is a good time of the year to test trace element levels in the herd.
Why is liver testing better than blood for copper?
Liver samples are preferred to blood samples for assessing copper status. The liver is the major storage site of copper in the body. Think of the liver as being like a water tank slowly feeding a trough (the blood). The trough remains full until the tank is empty and then the trough level also falls. Blood testing will identify clinical deficiency but does not give any indication of the level of copper reserves in the liver. Generally we are not looking for clinical deficiency but want to know whether there is enough copper reserve to get through the next period of time and how effective the supplementation programme has been.
Please contact Totally Vets to discuss the situation on your farm and for advice about assessing and treating a possible copper deficiency.
