Should I Feed My Horse Vitamin E This Winter?

Fall is here, Winter is coming, and pastures are readying themselves for dormancy. Your horse might need some extra nutrition this next season.

Feed program nutrition is a typical hot topic in the equine community, and every barn has its own. Training barns, breeding barns, or the casual adult amateur barn can all vary in what feed they stock and how much input an owner has in terms of what their horse eats.

Vitamin E is commonly supplemented in performance horses to encourage faster recovery from strenuous workouts and to help with muscle soreness. It’s also a crucial antioxidant to mitigate free radical damage at the cellular level and is often paired with other nutrients like selenium.

Most horses get plenty of vitamin E from grazing the lush spring and summer pastures, and these levels start to go down as the seasons change and grazing becomes more scarce through the fall and winter.

In areas where horses are stalled or in an environment where forage is dry hay-based, vitamin E levels are much lower year-round. When vitamin E levels are less than optimal, it can lead to prolonged recovery periods, a slower training progression, and, in young horses, slowed growth.

Vitamin E is considered an antioxidant and essential nutrient, meaning horses cannot make this element themselves; it has to come from their diet. Vitamin E can affect broodmare fertility, has incredible influence over a horse’s immune system, and affects recovery time after heavy periods of exercise.

Vitamin E is really an umbrella name; the term vitamin E encompasses multiple compounds that work together. The most impactful are alpha-tocopherol and gamma-tocopherol. Alpha-tocopherol is the most biologically available compound in the equine body and is what most vitamin E supplements contain.

Vitamin E deficiency can clinically manifest as neurologic symptoms, respiratory troubles, and difficulty maintaining or building a topline. Chronic tying up and increased fatigue and soreness, especially after workouts, are also common indicators.

Young horses and foals are particularly at risk of developing complications if they have low vitamin E levels, which can lead to overall stunted growth and development if not addressed.

Low vitamin E levels can exacerbate symptoms of already-present neurological conditions as well, like EPM. Chronically low levels can lead to vitamin E-deficient myelopathy and equine degenerative myeloenchephalopathy.

Vitamin E levels are checked by testing serum concentrations in a blood sample. The normal range of vitamin E serum levels is > two micrograms per milliliter, but this can vary slightly with each horse’s unique metabolism. Your vet will consider this when conducting their evaluations.

The National Research Council (NRC) recommends horses consume 1-2 IU per kilogram of body weight per day. The value the NRC uses to calculate nutrition requirements is 500 kg or 1,100 pounds. Recommendations can then be adjusted for each particular horse, but it gives a good ballpark of the value you’re looking for.

Based on the NRC recommendations, the average adult horse needs a minimum of 1,000 – 2,000 IU of vitamin E per day, not considering workload or other medical conditions.

The NRC designates 20 IU per kg of body weight as the upper safe limit of vitamin E intake, or around 10,000 IU per day. The risk of toxicity from too much vitamin E is considered low for horses, but there is such a thing as “too much.” There have been reported cases of impaired bone mineralization and coagulopathy in horses that have excessive vitamin E levels.

When comparing supplements you’ll find that synthetic vitamin E is often much less expensive than natural vitamin E, but you may find your self in a situation of “you get what you pay for.”

Natural vitamin E (d-alpha-tocopherol) is five times more bioavailable in the body compared to synthetic vitamin E (dl-alpha-tocopherol). Synthetic vitamin E is slower to raise serum levels than natural vitamin E and it takes a higher dose to make sure the horses’ body can actually access enough of the synthetic vitamin E by comparison.

Other studies that explored the effects of supplementing natural and synthetic vitamin E showed that horses going through an exercise program had better markers of lowered inflammation when taking natural vitamin E than those taking synthetic vitamin E1.

Vitamin E doesn’t just exist in grass forage. Fortified grains and balancers often have vitamin E in their nutrition profile. The levels can vary between brands and feed rates, so make sure to check your manufacturer label for more insight, or speak to a nutrition representative for the company.

For example, Triple Crown Senior has a feeding recommendation of 6 pounds per day for an average horse also receiving hay and 12 pounds per day for a horse that is not receiving hay. There are about 1,000 IU in 6 pounds of this particular feed.

As many of us horse owners know, not all horses need the amount of feed that instructions have on the bag. Easy keepers often get less than two pounds of grain a day, if that. If low amounts of grain are paired with lush grazing pasture, usually vitamin E levels aren’t a concern.

Other horses may have feeding situations, environments, or medical conditions that require limiting fortified grain or eliminating it from a diet completely. Dry lots, hay-only forage, limited turnouts and grazing time, or forage-pellet-only diets all could benefit from additional vitamin E supplementation, as these aren’t often fortified with essential nutrients a horse needs.

Vitamin E is our rock star in this article, but like a well-oiled machine, everything works together with other microsystems so that the whole horse functions properly.

Vitamin E and oxidative stress are often subjects that coincide, and there are other nutrients at play that contribute to limiting oxidative stress including Vitamin A, its precursor beta carotene, and vitamin C2. Selenium has a major role as an antioxidant, too, and is often paired with vitamin E supplements.

Vitamin A is actually the second step in the story; it’s synthesized in the equine digestive tract from its precursor beta carotene. As a fellow antioxidant, it’s also fat soluble and is plentiful in fresh grazing.

This antioxidant is essential for reproductive processes, vision development, and immune system function. Pregnant mares generally have a higher requirement of this nutrient, and it is commonly supplemented in fortified grain made for gestating mares.

Vitamin A is also stored in the horses’ liver, which is usually enough to tide horses over the winter months when fresh grazing isn’t necessarily available like it was in the spring and summer.

Like vitamin A, vitamin E can also be stored in the liver and fatty tissues to tide a horse over the winter months, but this is often not enough to keep up with adequate serum levels, especially if a horse is in regular work.

Vitamin C is another antioxidant involved in immune system function and works the closest with vitamin E and selenium. Typically, horses don’t need extra supplementation of this water-soluble compound as it’s synthesized easily in the liver from glucose.

This antioxidant is also an enzyme co-factor that’s pivotal in hormone production, is involved in how iron is absorbed in the body, and supports the immune system and overall joint health. Horses that might benefit from vitamin C supplementation include older horses with compromised livers or chronic respiratory illness.

Selenium is commonly paired with Vitamin E supplementation, as most horse owners have been warned to check selenium values in their feed and supplements to prevent selenium toxicity, which can happen at a relatively low dose in some cases (one gram). The recommended daily intake of selenium is 3 mg for an average horse.

Most feeds and commercial supplements have a small amount of selenium in their formula, and most horses have enough selenium in their diets to prevent clinical deficiency and neurological issues.

Selenium toxicosis is statistically rare, however, and the hype of toxicity has most likely stuck around due to the fact selenium was known for its toxicity before it was ever explored as an essential nutrient. The scenario behind most toxicity cases was when horses would graze from soils high in selenium.

When in doubt, always consult with your vet when it comes to your horse’s nutritional needs. It’s difficult to “overdose” on vitamin E, and many horses can benefit from an additional few thousand IU to their diet, especially if they have an intense workout regimen or pasture is less than ideal.

After consulting with my mare’s chiropractor (who also holds a DVM license), she also concurred vitamin E would be a good addition to her feed, so I’m at minimum going to supplement vitamin E through the winter.

She gets a little over 1,000 IU a day from her ration balancer right now, and her pasture is currently struggling to recover from the harsh summer we had. She’s also in consistent work and will stay in consistent work through the winter, and has had some trouble with overall soreness as she’s continuing to have small growth spurts.

Go out and enjoy this beautiful fall season, it’s officially trail riding season for me!