Copper, Chromium & Selenium – Three Essential Trace Elements

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Trace elements are essential for normal body function. They are involved in the enzyme systems that control the many biochemical reactions that take place within the cells.

Three trace elements that are particularly important to the performance horse are Copper, Chromium and Selenium.


Copper has many functions. It is essential for bone, cartilage and tendon formulation, the utilization of iron in the formation of haemoglobin and in the formation of melanin, the black pigment in hair.

Copper deficiency can cause bones to become weak and brittle, hair colour to fade. It is especially important in young growing horses as the development of bone collagen relies on sufficient presence of copper.

In fact, lack of dietary copper has been associated with the development of O.C.D.

Anaemia may develop with very low levels of copper due to its effect on the mobilisation of iron.

The daily dietary requirement for an adult horse is between 80-115mg. High levels of other trace minerals can interfere with the uptake of copper, for this reason some mineral supplements have more copper than the recommended daily requirement. Toxicity from overly high levels is very rare.

It is important that horses receive a daily mineral supplement and that it contains copper.

Note: Copper and zinc need to be balanced. Too much of one can interfere with the uptake of the other. The ideal copper to zinc ratio is 1:3. Most feeds and pasture contain sufficient zinc (a horse needs 40 mg per day) but it is important to be aware that too much zinc will affect the uptake of copper. High zinc intake can occur from water obtained from some bores, a horse can tolerate high levels of zinc as toxicity is very rare but it is the effect on copper that is important.

Also a high concentration of iron in the diet can interfere with both zinc and copper absorption, making already low levels of these minerals even less available to your horse. Check that you are not feeding no more than 8 times more iron than zinc.

For example the most common mineral imbalance found in hay is too much iron combined with low zinc and copper levels.


Chromium exists in two forms, the inorganic metallic form (Cr6) which is toxic to animals, and the organic form (Cr3) which is non-toxic and therefore is able to be fed as a supplement. Chromium is a constituent of a biochemical involved in the metabolism of carbohydrates and fats.

The benefits of chromium as an essential nutrient have been recognized by human athletes for years. Studies have shown how daily supplementation increases muscle gain and reduces body fat when combined with a physical training programme.

It is only since 1992 that equine researchers have clearly defined chromium’s role in improving health and performance in horses. Studies showed that horses on diets supplemented with 5mg of organic chromium per day had significant lower blood lactic acid levels after exercise when compared with control horses. Lactic acid is a by-product of energy metabolism. During intense exercise it accumulates in muscles and causes muscle fatigue. By supplementing with organic chromium, the length of time a horse can sustain a maximum effort during exercise is increased. Another benefit of chromium supplementation is the reduction in blood cortisol levels. Cortisol is commonly termed the “stress hormone” – Levels increase during stressful periods. Increased cortisol levels lead to a reduction in energy utilization and protein synthesis, important factors in the athletic horse.

More recent studies have shown that 5mg per day lowers blood insulin, especially in horses on high grain or high starch diets – such as performance horses, for example in racing. This means a more efficient use of glucose (ie energy) in the metabolism of the horse. Another study showed higher triglyceride values during exercise, possibly indicating more efficient fat mobilisation. Horses use fat for sustained energy.


Selenium’s most important function in the body is as a component of an enzyme called Glutathione Peroxidase – a powerful antioxidant.

As part of normal metabolism, cells produce waste products called peroxides. These substances are potentially dangerous to the integrity of the cell wall and must be neutralized quickly and efficiently. Glutathione Peroxidase is able to do this and hence protects the cell from the destructive effects of peroxides.

Because muscle cells metabolise large amounts of energy, they produce large amounts of peroxides. Selenium deficiencies usually manifest as muscle problems.

Large areas of New Zealand soils are deficient in selenium. Farmers often add Selenium in the form of pills. With horses, supplementation is a good idea, particularly horses in full training. Breeding horses have also been shown to benefit from regular selenium supplementation.

Before supplementing with selenium – it is important to take a blood test to assess the levels in the horse as too much selenium will be toxic and cause ill health, excessive in a short period may prove fatal. Check out the requirements and ways to supplement Selenium in our article ‘Selenium – What, Why, How’.

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