COPPER deficiency is a common condition that can occur in horses and now is a good time to remind breeders, owners and producers of this condition, what signs to look out for and the correct diagnosis and treatment of it.

I’m reminded of a previous call-out I received in the past to treat a bay thoroughbred foal which had been purchased in America a month previously.

The foal was in poor condition, had a reduced appetite, a dull (coppery) coat and a respiratory infection.

Discussion with the owner revealed that he had wormed the foal, kept it in, rugged it up and fed it on good quality hay and concentrates. I was aware that all the other foals in the yard were in top condition so immediately I was suspicious that there was something unusual at play.

We ran routine bloods to check the red and white cells. The results showed that the foal was anaemic and that his immune system was actively trying to fight off infection. I prescribed a five-day course of antibiotic treatment for the respiratory infection.

However, there was a poor response to this treatment and I began to wonder what else might be at play.

I ran some extra bloods for mineral and vitamin levels and the results indicated a severe copper deficiency.

I put the foal onto an oral copper treatment. Within four weeks, we began to see a notable improvement. The appetite increased and the respiratory infection cleared up. The coat began to return towards a normal colour and the foal began to put on condition. Fresh bloods indicated that the red blood cell count was rising back to normal levels and that the infection was under control.

This was a very interesting case and it illustrates how easily a mineral deficiency can cause health issues for a horse.

The key fact here is that once the deficiency was diagnosed, there was a rapid response to treatment.

Importance of copper in the horse

Copper is a vital mineral for normal metabolism in the horse.

It has an important link to red blood cells in the body. Prolonged deficiency can cause anaemia. Iron is essential for the formation of red blood cells and copper contains enzymes that are essential for the mobilisation of iron from its stores in the liver, spleen and bone marrow.

Copper has an important link in the process of mineralisation of bones. In young horses, especially foals that are gaining weight rapidly, low levels of copper can be a factor contributing to the development of epiphysitis.

In this condition, weak poorly mineralised bones come under pressure from the increasing weight of the musculo-skeletal system of a growing animal. The growth plates at the ends of the long bones swell and become distorted. This is manifested by swollen joints. If untreated, this can lead to permanent damage.

  • Signs of a copper deficiency: Copper is important in pigmentation and keratinisation. Signs of deficiency include a lack of pigment in the hair. For example, a bay animal will appear to have a coppery-coloured coat. Copper is also involved in the formation of keratin and so has a role in hoof health. Severe deficiency can lead to poor hoof development and growth, causing feet problems such as cracked hooves and white line disease. It must be said that it is only one possible cause of these hoof problems but it should be considered as a possible cause especially if the horse is displaying some of the other symptoms of copper deficiency already described above. Copper deficiency may also be a factor involved in fertility problems in mares.

    • How does the deficiency occur?

  • Primary deficiency: This is where there is insufficient intake of copper because of a lack of copper present in the grass, the forage or the concentrate feed. Geologically, certain parts of Ireland are naturally low in copper. And on a more local basis, certain fields on a farm can be low in copper.
  • Secondary deficiency: This is where copper is available but other elements interfere with its availability to the animal. In pasture, zinc can block the level of copper available in the grass. Whereas in the horse’s body after ingestion, molybdenum can block the absorption of copper into the bloodstream.
  • Diagnosis of a deficiency Blood testing is the method used to ascertain the presence of and the level of a deficiency in a horse. Soil, forage and concentrate food can all be tested for copper levels. This can be useful in tracing the source of the deficiency.
  • Treatment Once diagnosed, the horse can be put on a course of copper treatment. This can be administered orally as a drench on a daily basis or at time intervals decided by your veterinary surgeon. There is a slow-release injection form available. Many copper supplements are also available to mix in the feed or to feed Ad Lib in mineral licks. If you are suspicious that your horse is copper deficient, you should discuss the situation with your veterinary surgeon and get their advice as to what step you need to take next.

    • Denis Doyle MVB MRCVS is a veterinary surgeon in Wicklow town and is a member of the Equine Group of Veterinary Ireland.

    Email: hq@vetireland.ie

    Telephone: 01-4577976