Zinc (Zn) is an essential trace mineral that is required in the horse’s diet to support the proper function of many enzymes and proteins. It is involved in antioxidant protection, immune function, protein synthesis, and cellular communication.
Zinc is also important for proper bone development in foals and supports healthy hooves and skin. It is critical for reproductive health and supports normal growth and tissue health.
Zinc is commonly fed to horses that are easy keepers or horses with metabolic issues. Zinc can support healthy blood sugar levels by improving insulin sensitivity and boosting antioxidant status which might be lacking in horses with EMS.
It is important to balance levels of copper, iron, and zinc in your horse’s feeding program. High iron can interfere with copper and zinc absorption from the gut, causing your horse to develop signs of deficiency even if these minerals are fed at adequate rates.
Wheat bran, wheat middlings and brewer’s grains are good sources of zinc in the equine diet. Most forages are low in zinc, particularly if they are grown in areas with low levels of this mineral in the soil. Horses that are on forage-only diets are likely to require supplementation.
Mad Barn’s Omneity mineral and vitamin supplement provides zinc in a balanced formula designed to meet the core nutritional needs of the majority of horses. You will also find zinc in our AminoTrace+ mineral and vitamin formulated specifically for metabolic horses.
The feeding rate for zinc depends on your horse’s individual requirements and current diet. To determine the appropriate supplementation rate for your horse, submit your horse’s diet for analysis and one of our nutritionists will provide a complementary review.
Benefits of Zinc for Horses
Zinc is a co-factor for hundreds of enzymes in the horse’s body affecting a diverse range of physiological functions. Enzymes are proteins that carry out reactions in the body, such as breaking down sugars and fats for energy.
As an enzyme co-factor, zinc is required to help catalyze many biochemical reactions. This is why zinc supports so many functions in the body from antioxidant protection to hoof health and coat quality.
Zinc is the second-most abundant trace mineral in horses behind iron. It is found in all cells and tissues with the majority (80-85%) found in skeletal muscle and bones.
Below are the top 10 reasons why horses need adequate zinc in their diet:
1. Antioxidant Protection
An important function of zinc is to support antioxidant defenses. Both copper and zinc are found in a key antioxidant enzyme, superoxide dismutase (SOD). Zinc is also involved in regulating the production of other antioxidant enzymes. 
These enzymes converts harmful oxidants or free radical particles into neutral, harmless compounds. Free radicals are produced naturally by cells when nutrients are broken down for energy, but over time they can cause damage to cells.
By improving antioxidant status, zinc protects against premature aging and supports healthy tissues and cells. Horses that are heavily exercised produce more harmful oxidants and could benefit from additional antioxidant support.
In a research study, heavily exercised Thoroughbreds were fed an antioxidant supplement containing zinc and copper. The horses on the supplement experienced improved antioxidant capacity during the training period. 
Senior horses also tend to have lower levels of antioxidant enzymes and may benefit from zinc supplementation.
2. Hoof Health
A proper balance of zinc to copper helps support keratin synthesis. Keratin is the main protein in hooves that creates a strong hoof structure.
Horses meeting their zinc and copper requirements have lower risk of white line disease (also known as seedy toe) and lower incidence of hoof wall separation. 
3. Immune Function
Zinc helps immune cells respond to infections. When infection is detected, zinc levels in the blood drop as this mineral is taken up by immune cells and the liver. The temporary decrease in blood zinc during infection has been shown in horses affected by fever and cellulitis. 
Zinc enables immune cells to send out signals to other cells to coordinate an immune response. These immune signaling molecules are known as cytokines.
More research is needed to determine whether supplementing horses with zinc while they are fighting an infection is beneficial. It is theorized that adding zinc to diets that are otherwise low could improve the immune response.
4. Skin Health
Zinc deficiency in horses can cause skin abnormalities such as slow wound healing. This may be attributed to a weakened immune system.
Horses with low zinc might be more susceptible to mud fever or rain scald – a type of bacterial overgrowth on the skin that occurs in damp conditions. If immune function is impaired because of low zinc, the skin can become overwhelmed by bacteria.
Having adequate levels of zinc in the diet can support healthy skin and improve coat quality and sheen.
5. Insulin Levels and Insulin Sensitivity
In other animals including humans, low levels of zinc in the blood are associated with insulin resistance and diabetes. This mineral affects insulin secretion from cells in the pancreas. It may help ensure the right amount of insulin is released to manage blood sugars. 
Zinc is also involved in maintaining insulin sensitivity. This refers to how well cells respond to insulin to move glucose out of blood. In humans, zinc supplementation has been shown to improve insulin sensitivity in obese people. 
Zinc’s affect on insulin sensitivity has not been directly studied in horses. However, zinc is crucial for supporting antioxidant status and oxidative stress is a key contributor to insulin resistance. Ensuring adequate zinc intake may reduce the risk of metabolic dysfunction.
It is especially important that easy keepers and horses with equine metabolic syndrome or Cushing’s/PPID meet their zinc requirement to support proper insulin action.
6. Joint Health
Zinc is required to make the protein collagen which is a major part of tendons and ligaments in joints. It is also required for cartilage production.
In one study, moderately exercised yearlings were supplemented with a blend of copper, zinc, cobalt and manganese in either organic or inorganic forms. After 12 weeks, the horses fed the organic minerals had higher levels of markers for collagen synthesis.
These horses may be able to maintain heavier work loads and may be less susceptible to wear and tear in their joints. 
This study also shows that organic trace minerals are better able to support collagen production in joints than inorganic minerals. This study utilized zinc methionine as an organic source of zinc.
7. Coat Quality and Pigmentation
Zinc is involved in making the protein keratin which is the most abundant protein in hair. Keratin is responsible for giving hair its structure.
Horses supplemented with organic forms of zinc and copper had stronger and more elastic hair fibres than those given inorganic forms of these minerals. 
Zinc is also a component of the enzyme tyrosinase which makes melanin – the pigmentation protein that give skin and hair its colour.
Horses with dull, faded and frizzy hair might be low in zinc and might not be making enough melanin. Deficiency is most noticeable in chestnuts, bays, and blacks who require more melanin for their dark coat colour. These changes in coat colour and quality can also be a sign of copper deficiency.
Zinc and copper should be present in the diet in a 3:1 ratio to support a shiny, healthy coat.
8. Counteract High Iron Diets
Horses fed forages that are high in iron are at greater risk of poor hoof condition, liver disease, and insulin resistance.
Too much iron in the diet can interfere with zinc and copper absorption. This can lead to poor liver function, anemia (low red blood cell count), metabolic dysfunction, and laminitis.
If your horse consumes hay or other feed that has elevated iron, adding more copper and zinc to the diet can help balance mineral levels and prevent negative consequences. Equine nutritionists typically aim for a ratio of 4:3:1 of iron to zinc to copper in the overall diet.
Zinc deficiency can result in poor appetite, weight loss, and poor growth. Foals that are severely deficient have been shown to exhibit low appetite and slow growth rates.  This is related to changes in brain chemistry within the hypothalamus, which regulates food intake.
Zinc supplementation has been shown to stimulate appetite and support weight gain in people with anorexia. Ensuring adequate zinc intake in horses could support a normal appetite and healthy weight gain.
10. Gene Expression
Zinc is involved in over 300 metabolic processes through its role in regulating which genes are turned on.
All cells in the body have the same DNA or genetic code but cells of different tissue types have different genes turned on or off to allow these tissues to perform their unique functions. The genes that are expressed to make proteins can be regulated by signals outside the cell.
Zinc-finger transcription factors are special proteins that interpret these signals and bind to appropriate locations on the DNA to turn off or on specific genes. Not having enough zinc in the body might cause some of these proteins to not function properly.
This could learn to issues in cellular function related to dysregulation of gene expression and protein synthesis.
Zinc is a trace mineral that is required in miniscule amounts in the equine diet. Adding a zinc supplement on a one-of basis might create imbalances with other minerals, especially copper.
For this reason, we recommend evaluating the whole diet before feeding supplemental zinc to your horse. You can submit your horse’s diet for analysis and one of our nutritionists will be happy to provide a complementary review.
Signs of Zinc Deficiency in Horses
Most horses have sufficient intake of zinc from fresh grass and hay in their diet to avoid deficiency. However, imbalances with other minerals might affect zinc absorption and lead to deficiency even when there are adequate levels in the diet.
In other words, just because your horse gets enough zinc in their daily feed does not necessarily mean they absorb enough of this mineral from their diet.
Some common signs of zinc deficiency in the horse are:
- Insulin resistance which might present as increased thirst and urination, poor tolerance to sugars, more frequent or more severe laminitis, or irregular fat deposits like cresty neck
- Dull, faded coat that appears sun-bleached
- Poor hoof quality including cracked, brittle hooves that lose shoes easily
- Orthopedic disease including poor bone formation in foals and weak, painful joints in mature animals
- Poor appetite leading to loss of condition
- Hardened, crusty skin that is more susceptible to infections and/or hair loss
If levels in a growing horse’s diet fall below 40 mg/kg of feed, the horse is likely to show signs of deficiency including poor appetite and growth, dandruff, hair loss and developmental orthopedic diseases.
Factors Leading to Low Zinc Levels
There are several factors that can affect how zinc is absorbed and used in the body. The most well-described are interactions with other minerals that influence absorption or uptake from the gastrointestinal tract.
It is well known that zinc, copper, and iron all compete for the same absorption channels in the gut. If your horse consumes forages high in iron, this can impair zinc and copper absorption from the diet. Elevated iron levels in the body can also affect how zinc is used by tissues.
Forage-heavy diets might also result in large amounts of undigested fibre in the intestinal tract. This undigested fibre can bind to minerals and make them unavailable for absorption.
Phytates and high levels of calcium in feed have also been shown to decrease zinc bioavailability. 
Given the complexity of mineral and nutrient interactions, it is highly recommended that you consult with an equine nutritionist before adding any vitamins or minerals on a one-off basis. You can submit your equine diet online at this link for a complementary assessment by one of our equine nutritionists.
How to Assess Zinc Levels
There are no good biomarkers for zinc status in animals. Levels of this mineral in the blood only reflect about 0.1% of total zinc in the body.
Horses might show signs of deficiency long before any measurable changes can be observed in the blood.
Furthermore, dietary deficiency is not the only thing that can affect blood or serum levels of zinc. Other factors like age, stress and illness can temporarily affect how much of this micromineral is found in the blood.
The best way to assess whether your horse has any mineral imbalances and whether they would benefit from supplemental zinc is to assess nutrient levels in your horse’s overall feeding program.
How Much Zinc Should You Feed Your Horse?
Zinc is a 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 40 mg zinc per kg of dry feed . This is approximately 400 mg per day for a horse consuming 10 kg of dry feed daily.
Some horses might require more zinc than the recommended daily intake of 400 mg per day. For example, horses engaged in moderate to heavy exercise require approximately 500 mg per day.
Common feedstuffs like forages and grains typically contain 15 – 40 mg zinc per kg of dry matter. This varies greatly by geographic region depending on how much of this mineral is in the soil.
Mature horses can tolerate relatively high levels of zinc in their diet. The estimated upper tolerable limit is 500 mg/kg feed, or 5000 mg per day.
Toxicity might occur in industrial areas where pasture grasses contain very high levels of zinc. Growing animals are more sensitive to excess zinc and may develop lameness, swollen joints, or poor bone growth. 
Rather than feeding your horse supplemental zinc 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 Supplements contains approximately 500 mg of Bioplex zinc in a typical serving size for a 500 kg horse. It also provides all other essential minerals and vitamins that your horse needs at levels scientifically formulated to bring the majority of equine diets into balance.
Our AminoTrace+ Mineral and Vitamin Supplement is designed specifically for horses with metabolic issues and to counteract high iron intake. A serving of AminoTrace+ contain 760 mg of Bioplex zinc.
Best Zinc Sources for Horses
Equine zinc supplements comes in many different forms. Commercial premixes may contain zinc from inorganic sources or organic sources.
Common inorganic sources include:
- zinc oxide
- zinc sulfate
Common organic sources include:
- zinc proteinate
- zinc nicotinate
- zinc methionine
There is conflicting research in horses on which form is best. One study found zinc oxide had better retention (less excretion) compared to a zinc amino acid complex. However, other studies suggest organic forms are better absorbed and utilized by the body.
Organic zinc amino acid complexes can be absorbed through amino acid transporters on the intestinal wall and not just the zinc channels which copper and iron compete for. Horses with high iron may experience greater benefits from organic forms.
Studies that look at functional outcomes like hoof quality, joint health, and coat quality also consistently show better outcomes with feeding organic sources such as zinc proteinate. These forms are metabolized slowly by the body and can be safely stored in cells.
Zinc amino acid complexes such as zinc methionine mimic how most minerals are naturally found in forages and grains, bound to one or more amino acid molecules or entire proteins.
Mad Barn’s vitamin and mineral premixes use Bioplex zinc to provide a highly bioavailable form of this mineral. Bioplex zinc is a proprietary chelated compound that is bound to amino acids, allowing efficient absorption.
This form of zinc remains stable in the digestive system and does not cause stomach or gut disturbances.
Risk of Toxicity and Side Effects
Areas with industrial activity such as mining and smelting can have extremely high levels of zinc in pastures – up to 20,000 ppm.
Foals that have been weaned and are let out on these pastures are most at risk for having serious side effects to zinc toxicity. Signs of toxicity in these foals include:
- enlarged joints
- abnormal bone formation
- rough coat 
Mature horses are not as susceptible to zinc toxicity but elevated intake might result in a secondary copper deficiency. This could leading to poor coat quality, more frequent illness and anemia.
Typical supplementation rates of 500 mg per day will be safely under the upper tolerable intake limit of 5,000 mg per day even if fed on top of a diet that is already supplying adequate levels of zinc.
Most horses receiving a zinc supplement will need adjustments in other nutrient levels to ensure mineral balance is maintained. Zinc is usually fed at a 3:1 ratio with copper.
To determine whether your horse could benefits from additional zinc in their diet, we recommend submitting your horse’s feeding program for analysis online. Our equine nutritionists are available to answer any questions you might have about your horse’s diet.
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