Vitamin E is an essential nutrient for horses, much like it is for humans and other animals. Vitamin E cannot be made and must be obtained from the diet. It plays a vital role in various bodily functions including immune system support, muscle function, and the elimination of free radicals that can damage cells and tissue. Horses that have access to fresh, green pasture typically get an adequate amount of Vitamin E from their diet. However, those that are kept in stables/stalls or fed on a diet consisting mainly of hay might require supplementation.
What is Vitamin E
Vitamin E refers to a group of fat-soluble compounds with distinctive antioxidant activities. One of the most known and studied forms of vitamin E is tocopherol. There are four types of tocopherols: alpha, beta, gamma, and delta. Each type has its unique composition and activity.
- Alpha-Tocopherol (α-tocopherol): Found in a variety of foods, including vegetable oils (such as olive oil and sunflower oil), nuts, and seeds. It’s the most active form in our bodies and is known for its potent antioxidant properties. It helps to fight free radicals, supports immune function, and promotes skin health. Often used in vitamin E supplements and skincare products.
- Beta-Tocopherol (β-tocopherol): Less common in the diet but still found in certain nuts and seeds. Has antioxidant properties but is not as potent as alpha-tocopherol.
- Gamma-Tocopherol (γ-tocopherol): Found in maize (USA> corn), soybean oil, and some nuts and seeds. Has been shown to have anti-inflammatory and antioxidant properties. Also, helps to scavenge and neutralize free radicals.
- Delta-Tocopherol (δ-tocopherol): Found in smaller amounts in the diet. Possesses antioxidant properties but is less active than alpha and gamma tocopherols.
Key Functions of Vitamin E in Horses
Muscle: Vitamin E is a powerful antioxidant that helps protect cells from oxidative damage caused by free radicals. It supports healthy muscle function and can help in muscle disorders like Equine Motor Neurone Disease and tying-up syndrome.
Immune function: Vitamin E supports the immune system, helping the horse fight off infections and illnesses. Its also important in inflammatory conditions such as Sweet-itch and equine asthma.
Nervous System Health: Adequate levels of Vitamin E are crucial for the proper function of the nervous system.
Reproductive Health: It is also involved in the reproductive processes and can be beneficial for breeding horses. Fertility: Adequate levels of Vitamin E are associated with improved fertility in mares. It may enhance the quality of the uterine environment, supporting conception and early embryonic development. Pregnancy: During pregnancy, Vitamin E helps in the development of the foetus and supports the mare’s overall health. Its antioxidant properties can protect the developing foetus from oxidative stress. Lactation: Mares need an increased level of Vitamin E during lactation to ensure that the milk is nutritious and supports the foal’s immune system and overall growth. In Stallions: Sperm Quality: Vitamin E can impact sperm quality positively. Its antioxidant properties protect sperm from oxidative damage, ensuring motility and viability. Libido: There’s some evidence that adequate levels of Vitamin E can support healthy libido in stallions, although more research is needed in this area. For Foals: Foals can benefit from Vitamin E through the mare’s milk, which helps to strengthen their immune system and supports healthy growth and development. Muscle Development: Vitamin E is essential for muscle development and function. Deficiency in foals can lead to muscle weakness and other health issues.
Signs of Possible Vitamin E Deficiency in Horses:
- Muscle weakness or atrophy
- Difficulty in walking or coordination issues
- Lowered immune response
- Nervous system disorders
Supplementation of Vitamin E
Natural Vitamin E (d-alpha-tocopherol) is more easily absorbed and utilized by the horse’s body than the synthetic form (dl-alpha-tocopherol). The correct dosage of Vitamin E depends on various factors including the horse’s size, age, and overall health. It’s important that for horses to get the maximum benefit from Vitamin E that they also have sufficient selenium. Selenium can be fed as either the inorganic form, most commonly sodium selenite or as an organic form, most commonly selenised yeast – yeast which has been grown on a medium rich in selenium. Inorganic selenium has a low toxicity threshold in horses and ponies and care must be taken, especially if the diet contains several sources of selenium e.g. hard feed and supplements or you are in an area with high soil selenium. A map showing soil selenium levels in the UK is available here> https://www.ukso.org/static-maps/advanced-soil-geochemical-atlas-of-england-and-wales/selenium-high.jpg Areas that are particularly high include Cornwall, parts of North Devon, West Wales and much of the North-West. It is generally considered that a horse or pony should not be fed more than 8mg/500kg (0.016mg/kg) of inorganic selenium per day.
Symptoms of Selenium Toxicity in Horses
- Hoof Issues: One of the most common signs is a change in the hoof. The horse may experience hoof soreness, cracking, and sloughing of the hoof, or the coronary band may become soft or even slough off.
- Hair Loss: Loss of mane and tail hair is also a common symptom.
- Lameness: Affected horses can exhibit lameness due to hoof issues.
- Colic and Diarrhoea: Gastrointestinal issues like colic and diarrhoea can occur.
- Liver and Kidney Damage: In severe cases, it can lead to liver and kidney damage.
- Respiratory Distress: Breathing problems due to damage to lung tissues.
- Nervous System Issues: In very severe cases, neurological problems can occur.
Treatment involves identifying the source of excessive selenium and remove it immediately. This could involve changing the horse’s diet, avoiding certain pastures, or adjusting supplements. If you suspect selenium toxicity then its essential to contact your vet immediately.
Below is a guide to how much Vitamin E to supplement with for different needs/conditions.
|Amount per day of Vitamin E for a 500kg horse||Minimum||Recommended|
|Mature horse (Maintenance)||500IU per day||1000IU per day|
|Growing horses||800IU per day||1600IU per day|
|Broodmares & Stallions (non-breeding)||1000IU per day||2000IU per day|
|Broodmares & Stallions (breeding)||1400IU per day||3000IU per day|
|Mature horse – Hard Work||1000IU per day||2000-4000IU per day|
|Racehorse (2yo) – Moderate to Heavy exercise||1500IU per day||3000IU per day|
|Horses needing muscle support||500IU per day||2000-3000IU per day|
|Mares in foal (Last 3 months)||1500IU per day||4000IU per day|
|Lactating mares||800IU per day||2000IU per day|
|Recovering horses||500IU per day||3000IU per day|
|Horses receiving oil in the diet||1IU/ml of oil||1IU/ml of oil|
|Horses needing immune support||500IU per day||3000IU per day|
|Horses needing respiratory support||500IU per day||2000-3000IU per day|
|Older horses (>15 years of age)||600IU per day||3000IU per day|
What is the difference between mg and IU?
Sometimes Vitamin E is expressed as the weight in mg or as IU, which stands for International Units. The two are related but slightly different. The weight is the same for different forms of Vitamin E but the IU is how it works in the body or the activity. So for example, for 1 mg of synthetic Vitamin E the biological activity in the body would be equivalent to around 1.5 IU. Feeding 100mg of Vitamin E would therefore give you 150 IU of Vitamin E activity.
Vitamin E Supplements
If you are looking for a Vitamin E supplement for your horse or pony then we have a guide on the website where many of the common Vitamin E supplements on the market have been compared. Click here to read – Vitamin E Supplements for Horses Compared and its Uses.
Vitamin E Toxicity/Overdose
Vitamin E overdose in horses is relatively rare but can occur, particularly if an owner misinterprets the dosage requirements or isn’t aware of the horse’s overall vitamin E intake from all dietary sources.
Symptoms of Vitamin E Overdose in horses:
The specific symptoms of vitamin E overdose in horses aren’t well-documented since it’s a rare occurrence. However, excessive vitamin E can potentially interfere with the action of other fat-soluble vitamins, leading to imbalances and health issues. It might also have an anticoagulant effect, increasing the risk of bleeding.
- Vitamin Imbalance: Excessive vitamin E can disrupt the balance of other vitamins in the body, leading to deficiencies or imbalances.
- Increased Bleeding Risk: Vitamin E has natural anticoagulant properties; an overdose can potentially enhance this effect, leading to an increased risk of bleeding.
- Muscle Weakness: Although not well-studied in horses, in other animals and humans, very high doses of vitamin E can lead to muscle weakness and other health issues.
- Digestive Issues: In some cases, an overdose can lead to gastrointestinal disturbances.
Vitamin E plays many important roles in keeping horses and ponies healthy. Horses and ponies that are not receiving fresh forage may require supplementation, especially if they are old, in hard work or have muscle or respiratory issues. Vitamin E is generally safe but should not be over-supplemented. Vitamin E also requires selenium to work most effectively. If you are using a Vitamin E supplement, then it may have selenium added. Organic selenium sources of selenium, such as selenised yeast are safer than inorganic sources (e.g. sodium selenite).
Learn More about Vitamin E
- Article – Feed Materials In Focus – Vitamin E Supplements for Horses Compared
- Podcast –
- Article – Can vitamin C help my horse breathe?
- Article – Feed Materials In Focus – Vitamin E Supplements for Muscle Support Reviewed.