Copper (Cu) is an essential trace mineral that is required in the equine diet to support the proper function of many enzymes in the horse’s body.

Copper is important for iron metabolism, healthy connective tissue, energy production and antioxidant protection.

Horses might be low in copper due to low levels in their diet or because their diets have high levels of zinc (Zn) or iron (Fe). Excess intake of zinc or iron can interfere with copper absorption from the gut.

Copper and zinc levels need to be carefully balanced with each other to ensure proper absorption of both minerals from the digestive tract. A three-to-one (3:1) ratio of zinc to copper is recommended for most horses.

One of the most obvious signs of potential copper deficiency is a change in coat colour due to loss of pigmentation. The coat might appear dull, frizzy or discolored with a reddish tinge.

Copper deficiency can also cause anemia and weakened blood vessels, bones, or joints in adult horses. In young growing animals, low levels of copper can cause abnormal bone and cartilage formation. [1]

Copper toxicity in horses is extremely rare and requires very high intake of this mineral. However, high levels can reduce absorption of selenium and iron and interfere with how these are used by the body.

Mad Barn’s Omneity Premix is a fully balanced equine mineral and vitamin supplement that provides comprehensive nutritional coverage for your horse’s needs.

It contains 1000 mg/kg copper in the form of highly absorbable Bioplex copper, a source of copper proteinate that is organic and better used by the horse’s cells.

Our AminoTrace+ mineral and vitamin supplement provides higher copper content at 1500 mg/kg. It is designed for horses with metabolic issues and for horses that need to counteract high dietary iron intake.

We also carry bulk Bioplex copper powder for horses that require additional supplementation and a 3:1 Zinc Copper supplement.

The feeding rate for Bioplex copper depends on your horse’s condition and current feeding program. To determine the proper inclusion rate for your horse, submit your horse’s diet for analysis and our nutritionists can help.

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Benefits of Copper for Horses

All mammals require copper in their diet to act as a co-factor in the function of numerous enzymes. Enzymes are proteins that catalyze various chemical reactions in the body.

These enzymes are involved in important tasks throughout the horse’s physiology including metabolism, organ function, detoxification processes, growth and more.

Having adequate copper levels allows optimal function of the enzymes in all cells of the horse’s body. This can contribute to overall well-being, better coat and hoof quality, energy metabolism, and much more.

Below are the top 10 reasons why horses need adequate copper in their diet:

1. Coat Colour

Copper is required for the enzyme tyrosinase which makes melanin, the colour pigment in skin and hair. Horses with dull, faded hair might be low in copper and may not be able to make enough melanin.

Copper can support melanin production to protect against sun-bleaching and promote proper colouring, especially in chestnuts, bays, and blacks.

2. Hoof Health

Copper supports hoof health, not only when applied directly to hooves but also when levels within the body are optimized. Proper balance of copper and zinc supports the synthesis of keratin – a protein that contributes to the structural integrity of hooves.

Horses fed adequate levels of copper and zinc were shown to have lower incidence of white line disease (also known as seedy toe) with reduced risk of hoof wall separation. [2]

3. Hoof Growth

Copper has been shown to support hoof growth in yearlings and adult horses, especially when it is given in the form of copper proteinate instead of inorganic copper salts.

Supplementing the horse’s diet with copper and zinc proteinates increases the mineral content of the hoof horn which provides extra antioxidant protection and supports a strong hoof structure. [3][4]

4. Antioxidant Protection

Copper acts as an antioxidant by being part of the antioxidant enzyme copper/zinc superoxide dismutase. This enzyme exists in almost all cells of the body and protects against oxidant molecules that can cause damage to various parts of the cell.

Adequate antioxidant status protects against premature aging and helps cells and tissues/organs function properly.

Antioxidants are especially important for horses that are heavily exercised to help their tissues recover quickly. Older animals are also particularly vulnerable to low levels of antioxidants and might benefit from copper supplementation.

5. Immune Function

Low levels of the copper-containing antioxidant superoxide dismutase (SOD) can impair the function of the immune system.

Macrophages and neutrophils are immune cells that are found throughout the body. These immune cells rely on the SOD enzyme to generate hydrogen peroxide which is used to kill bacteria and prevent infection.

Horses with low copper and zinc status might be more prone to mud fever or rain scald because their immune cells are unable to protect against overgrowth of skin bacteria in humid conditions. [5]

6. Iron Metabolism

This micromineral is important for iron metabolism and the production of red blood cells. Iron is a critical part of red blood cells which carry oxygen around the body. Several copper-containing enzymes are responsible for moving iron from where it is stored to where red blood cells are formed.

Anemia (low red blood cells) in horses can be caused by copper deficiency because they are not able to make enough red blood cells. Horses with anemia may be weak, have low energy, poor exercise performance and low appetite.

7. Counteract High Iron Diets

Copper supplementation can counteract high iron intake in horses with iron overload. High iron intake is common in horses because it is found in almost all plant material, water, and soil. Excess iron in the diet can contribute to insulin resistance, laminitis and liver damage. It can also slow down copper absorption from the gut.

Equine nutritionists aim for a ratio of approximately 4:3:1 of iron to zinc to copper in the horse’s diet to have optimal levels of these three interconnected minerals. Adding copper to the diet of horses with high iron intake can help improve their metabolic health and support healthy hooves and liver function.

8. Bone Development in Foals

Copper supplementation is recommended for pregnant mares to support adequate copper status in the foal. This trace mineral is required for the enzyme lysyl oxidase which helps form strong connective tissue.

In growing animals, copper helps support proper growth of cartilage, tendons, and ligaments. Osteochondrosis, in which the connection between bone and cartilage is weak, can be due to copper deficiency in foals and is often related to copper-deficient diets in their dams. [6]

9. Energy Production

Energy production by all cells of the body requires copper. This element is a component of cytochrome c oxidase, which is an enzyme within the mitochondria. The mitochondria is sometimes referred to as the power plant of the cell; it is the part of the cell that makes energy from carbohydrates, fats, and proteins.

All cells of the body are dependent on this enzyme to produce adenosine triphosphate (ATP), the molecule that acts as the main energy currency of the cell. Optimal copper levels ensure that cells metabolize nutrients properly and get enough energy from them.

10. Nervous System Function

The nervous system requires copper to function properly. Copper is involved in the production and maintenance of myelin. Myelin is a protective sheath that covers nerves to help them send signals around the body properly.

Copper is also involved in the production of the neurotransmitter norepinephrine which allows nerves to communicate with each other.

Copper is a trace mineral that is only required in miniscule amounts in the equine diet. Adding copper on a one-off basis might create imbalances with other minerals, especially with zinc and iron.

We recommend evaluating the whole diet before adding supplemental copper. You can submit your horse’s diet for analysis and one of our nutritionists will be happy to provide a complementary review.

Signs of Copper Deficiency

Severe copper deficiency is rare in horses. However, suboptimal levels are common and can be part of the reason for observing the following signs of a potential deficiency:

  • Faded coat colour; this is often one of the first signs of a possible copper deficiency
  • Horses with copper deficiency might appear sluggish and tired
  • Lower than normal appetite
  • Hooves that are more prone to splitting or cracking and may lose shoes often
  • Thin soles, thrush, abscesses, or soft and weak hoof walls
  • White line disease caused by cracks in the hooves which allow bacteria to overwhelm the tissue
  • Tendon and ligament weaknesses due to impaired production and maintenance of connective tissues
  • Allergies such as hives and sweet itch
  • Persistent mud fever or rain scald due to a weakened immune system
  • Yellowish eyes, skin, or gums which might be a sign of jaundice in horses with copper-deficiency anaemia

In more serious cases the following symptoms may be observed:

  • Developmental orthopedic diseases such as osteochondrosis or osteochondritis dissecans; these are more commonly observed in young, growing horses
  • Aortic rupture; copper deficiency can weaken blood vessels and cause aortic rupture which is often fatal
  • Uterine artery rupture; this potentially fatal condition is caused by heavy bleeding during or after delivery and is more common in mares that are low in copper [7]

Factors Leading to Copper Deficiency

Low levels of copper in forage can contribute to inadequate intake in horses. Copper content of forages is proportional to the availability of this mineral in the soil which increases as soil pH decreases.

Crops grown in soil above pH 7.5 might have inadequate levels of this compound and should be analyzed for copper content.

Organic matter in soil can bind copper and prevent it from accumulating in plants. Forages grown in peat or on heavily manure-treated fields are more likely to have low levels of copper. [8]

Water is not thought to be a major source of this mineral and is unlikely to have much of an impact on copper status in the horse.

One of the most common reasons for a deficiency in horses is hay that is high in iron and low in zinc and copper. High iron can interfere with absorption of copper and zinc, further exacerbating the inadequate absorption of these minerals.

Horses on forage-only diets are more likely to have imbalances in these three minerals that can be corrected by supplementing these minerals in proper ratios.

High iron intake can have a number of negative effects on horses including liver damage, oxidative stress and insulin resistance and laminitis.

If you suspect high iron intake in your horses, consider feeding AminoTrace+ as your daily mineral and vitamin supplement. This ration balancer provides higher levels of copper and zinc to help counteract excess iron in the diet.

How to Assess Copper Levels

Blood tests are not routinely done to assess copper status in horses. Levels of this mineral in the blood can fluctuate greatly in response to the diet, management, and age of the animal.

This means that reliable reference values for copper have not been established in horses. [10]

Your veterinarian may use a blood test if a severe copper deficiency is suspected, such as in foals with poor bone formation.

The best way to assess whether your horse is likely to benefit from supplemental copper is to evaluate mineral levels in the whole diet.

How Much Copper Should You Feed Your Horse?

Given the complexity of mineral interactions and possibility for secondary deficiencies due to imbalances, it is highly recommended that you consult with an equine nutritionist before feeding vitamins or minerals on a one-off basis.

Copper is a micromineral, or trace mineral meaning it is required in smaller amounts compared to other macrominerals.

According to the National Research Council (NRC), the daily requirement for adult horses at maintenance is estimated at 10 mg copper per kg of dry feed, or approximately 100 mg per day.

The estimated upper tolerable limit of copper for horses is 250 mg/kg feed, or 2500 mg per day. [1]

Some horses might require more copper than the recommended daily intake. For example, horses with moderate to heavy exercise require approximately 125 mg per day to make up for copper lost in sweat.

Pregnant mares and growing animals require higher intakes to support proper growth.

Pregnant mares supplemented with 300 mg of copper per day in late gestation gave birth to foals with significantly lower inflammation of bone growth plates at 150 days of age compared to the offspring of mares that did not get additional copper. [1]

Foals can also be supplemented with approximately 100 mg of copper per day to help support healthy growth, particularly to help form strong bones and joints.

Rather than feeding your horse more copper in isolation, it is important to look at their diet as a whole. Minerals need to be fed in balanced ratios to ensure optimal health.

Mad Barn’s Omneity Equine Mineral and Vitamin contains 120 mg of Bioplex copper in a typical serving size for a 500 kg horse.

In addition to copper, Omneity provides all other essential minerals and vitamins that your horse needs at levels scientifically formulated to bring the majority of equine diets into balance.

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Copper Absorption

In all mammals, copper absorption can occur from the stomach to the end of the small intestine, with most of it occuring at the beginning of the small intestine.

Typically, copper is absorbed in the intestine through specific channels designed to move copper ions into the blood stream. High levels of zinc in the diet can interfere with these channels and block copper absorption.

This is another reason why it is important to consider all factors in the diet before making changes to individual components.

Copper that is absorbed from the diet travels to the liver where it is released into the blood bound to a special protein called ceruloplasmin. This protein carries copper in the bloodstream to bring it to other tissues of the body.

Molybdenum and Copper

You may have heard that high levels of the mineral molybdenum (Mo) in the diet can cause copper deficiency. This is far less likely in horses than in cattle and sheep.

Copper absorption is more likely to be affected by high levels of molybdenum in ruminants than in horses who are hindgut metabolizers.

Geographic areas with industrial activity including mining and smelting operations may have molybdenum contamination in soil. This can result in increased molybdenum accumulation in the plants grown there.

This has been theorized as contributing to copper deficiency in horses that consume forages grown in these areas.

However, even in experimental settings when high levels of molybdenum were applied to fields, consuming plants grown there did not affect copper status in horses. [9]

Therefore, excessive molybdenum intake is unlikely to be a primary cause for copper deficiency in horses.

Best Copper Sources for Horses

Inorganic sources of copper, known as copper salts, come in several forms. For example, copper chloride, copper acetate, copper sulphate and copper carbonate can be given to horses.

Of these, copper acetate has the highest bioavailability and copper carbonate has the lowest.

Copper sulphate is commonly applied directly to hooves to help deal with bacterial overgrowth in issues like white line disease. Experimental studies have shown that it given be orally to improve copper status in horses.

However, high levels of copper sulphate added to the horse’s diet can cause stomach and gut disturbances as well as damage to the kidney, liver and other organs. [11] [12]

Copper absorption from inorganic sources is limited by the number and availability of copper transport channels on intestinal cells. High zinc levels can block these channels and hamper absorption in the intestine.

Other forms of copper that don’t rely only on copper transport channels have higher absorption. For example, chelated copper (cupric chelate) can be provided as copper bound to the amino acids lysine or methionine.

This allows copper absorption to occur through transporters that move lysine and methionine into the bloodstream for more efficient absorption.

Mad Barn’s vitamin and mineral premixes use Bioplex copper to provide a highly bioavailable form of this compound.

Bioplex copper is a proprietary form of chelated copper that is bound to amino acids, allowing efficient absorption.

This form of copper remains stable through the stomach and does not cause stomach or gut disturbances. It also lessens environmental damage because the efficient absorption means less copper is excreted in fecal matter compared to other sources. [13]

Risk of Toxicity and Side Effects

The estimated upper tolerable limit of copper for horses is 250 mg/kg feed, or 2500 mg per day. Horses consuming a regular diet of forages and grains are unlikely to reach this level.

Acute copper toxicity has been reported in horses given supplemental copper sulphate in a scientific experiment.

These horses were fed an extremely high dose of approximately 62 grams given directly into the stomach which caused stomach and gut issues. Several repeated doses caused jaundice, impaired the formation of red blood cells and caused organ failure. [11]

This extreme toxicity would not occur with copper supplementation at the levels found in common commercial mineral and vitamin mixes.

Particularly, when organic forms are used, like Bioplex copper proteinate, the risk for toxicity is much lower because this molecule is metabolized slowly like an amino acid.

One study reported that diets low in Vitamin E and high in copper and iron pose an increased risks for equine motor neuron disease (EMND). [14]

In a comprehensive review of several experiments, researchers concluded that low vitamin E intake is a greater risk factor for EMND than high copper intake. [15]

Research in Horses

Hoof Health

In one study at the University of Florida, yearlings were given zinc, manganese and copper either in the form of proteinates or as inorganic forms of these minerals.

Horses that were given the minerals in the proteinate form had 4% faster growth in hooves than those given inorganic sources. This suggests that feeding organic sources of minerals like copper proteinate results in better hoof health than feeding inorganic sources. [4]

In another study, adult warm-blooded horses were either given supplemental organic sources of zinc and copper (total Cu intake 84mg/day) or no supplemental zinc and copper (total Cu intake 64 mg/day).

After 9 months, horses given supplemental copper had significantly higher levels of copper and zinc in hair and hoof samples. The supplemented group had faster growth of the hoof horn and good hoof quality. [3]

In an observational study, nutritionists investigated why the incidence of white line disease at a single riding stable was high one year and not the next.

They concluded that in the years with more white line disease the horses had lower intakes of zinc and copper. [2]

Skeletal Development in Foals

It is especially important to ensure that mares on forage-only diets have sufficient copper in their diet during pregnancy to support healthy cartilage and bone formation in their foals. Copper deficiency has been identified as of the factors contributing to abnormal cartilage and bone formation in foals.

Supplementing mares with 0.5 mg of copper per kg of bodyweight every day during the final twelve weeks of gestation has been shown to increase the copper status of mares and their foals. The copper content of the liver of both mares and foals was increased by supplementation of the mares. [16]

In another study, mares were given supplemental copper during late pregnancy and their foals were given copper until 180 days of age. Foals that were born to supplemented mares and given supplemental copper had lower prevalence and severity of osteochondrosis (abnormal growth plates) and other cartilage abnormalities. [6]

There are many reasons to consider adding supplemental copper to your horse’s diet. Mad Barn’s Bioplex copper is a copper proteinate that is highly bioavailable and safe to feed.

However, it is important to consider levels of all minerals and vitamins in the diet when making changes to your horse’s feeding program.

To determine whether your horse needs supplemental copper, submit your horse’s diet for analysis online and one of our equine nutritionists will review nutrient levels for copper and other minerals.


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  1. Pagan, Joe D. Micromineral Requirements in Horses. Kentucky Equine Research, Inc.
  2. Higami, Atsuko. Occurence of white line disease in performance horses fed on low-zinc and low-copper diets. J Equine Sci. 1999.
  3. Jancikova, Petra et al. The Effect of Feed Additive Containing Vitamins and Trace Elements on the Elements Profile and Growth of Skin Derivatives in Horses. Annals An Sci. 2012.
  4. Ott, EA and Johnson, EL Effect of trace mineral proteinates on growth and skeletal and hoof development in yearling horses.. J Equine Vet Sci. 2001.
  5. Stafford, Sian L. et al. Metal ions in macrophage antimicrobial pathways: emerging roles for zinc and copper. Biosci Rep. 2013.
  6. Knight, Debra et al. The effects of copper supplementation on the prevalence of cartilage lesions in foals. Equine Vet J. 1990. View Summary
  7. Stowe, Howard. Effects of Age and Impending Parturition upon Serum Copper of Thoroughbred Mares. J Nutr. 1968. View Summary
  8. Vaage, Alan et al. Copper content of Ontario forages. Agri-food laboratories.
  9. Pearce, S.G. et al. The effect of high pasture molybdenum concentrations on the copper status of grazing horses in New Zealand. NZ J Ag Res. 1999.
  10. Stubley, Deirdre et al. Copper and zinc levels in the blood of Thoroughbreds in training in the United Kingdom. Equine Vet J. 1983. View Summary
  11. Bauer, M. Copper Sulphate Poisoning in Horses . Vet Arh. 1975.
  12. Pearce, S.G. et al. Effect of copper supplementation on the copper status of pasture-fed young Thoroughbreds. Equine Vet J. 1998. View Summary
  13. Jancikova, Petra et al. The effect of various copper sources on the trace elements profile in the hair, plasma and faeces and copper activity in the organism of horses. Acta Univ Agric. 2012.
  14. Divers, Thomas et al. Evaluation of the risk of motor neuron disease in horses fed a diet low in vitamin E and high in copper and iron. Am J Vet Res. 2006. View Summary
  15. Divers, Thomas. Vitamin E Deficiency Is A Risk Factor For Equine Motor Neuron Disease. 6th Mid-Atlantic Nutrition Conference. 2008.
  16. Pearce, S.G. et al. Effect of copper supplementation on copper status of pregnant mares and foals. Equine Vet J. 2010. View Summary