By Sarah Welk Baynum
Vitamin E is an essential nutrient for horses.
While many horse owners know Vitamin E is important, they may not understand exactly why it’s so essential—especially in the winter months.
Here’s why this primary antioxidant is not being naturally sourced as much during the winter, and some tips on how much horses need, when they might need it supplemented, and how to supplement Vitamin E.
The Importance of Vitamin E
There has been new research lately focusing on just how important Vitamin E is throughout the life of the horse.
One of the most important functions of Vitamin E is that it reduces free radicals that are produced during a horse’s everyday life, but especially during exercise.
That means while Vitamin E is very important for all horses, it’s particularly important for those who are exercising and in consistent work. This is because Vitamin E helps with muscle recovery and is also very important for neuromuscular health in general.
There are certain diseases horses can get that have been linked to Vitamin E deficiencies at different periods of their life. Some of these diseases are reversible, but unfortunately, some of them are catastrophic and irreversible.
Changes in the Winter That Affect Horses Natural Intake of Vitamin E
Horses that are coming off of pasture grass and eating more dry forage means a big change for them nutritionally.
Since Vitamin E is found naturally in fresh, green pasture grass, this change in forage type and quality means less natural Vitamin E intake starting in the fall months.
The amount of Vitamin E in grass is also going to range quite a bit depending on several factors. There are studies that now show that horses consume 350 to 3,000 IU (international units) of Vitamin E from pasture grass per day. If horses are on good quality pasture grass, such as in the spring and summer months, their Vitamin E needs are typically being met.
While there is still grass out in the pastures come fall, albeit likely overgrazed in many situations, that grass is not as nutrient-filled as spring and summer grass, meaning they source less Vitamin E from it. Once the grass goes dormant in the winter, it's no longer a source of Vitamin E anymore.
As horses are fully switched over to hay forage for the winter, this marks a significant change in the Vitamin E levels they source naturally.
When you cut grass, it dries and turns it into hay. Hay maintains a lot of nutrients even after the drying process and is a great source of necessary fiber for horses. But unfortunately, Vitamin E is one of those nutrients that's not very stable.
About 50% of Vitamin E is lost in the first month after cutting and drying. After a couple months of storage, hay has almost zero Vitamin E.
This is why we have to rely on other sources for horses to obtain Vitamin E, whether it’s because they're picking at dormant pasture grass or eating primarily hay as their source of forage during the winter.
Horses That May Need More Vitamin E than the Average Horse and Deficiencies
Some horses, however, need additional Vitamin E even when they have access to good grass.
For example, horses with neuromuscular issues and horses with PSSM type 1 or type 2 may need more because they have some additional stressors on their musculature.
Horses with EPM, or other neurological conditions, may also need more Vitamin E because they're using up the Vitamin E that they're consuming more quickly than the normal horse due to the underlying disease.
Unfortunately, it’s hard to tell if your horse might be experiencing Vitamin E deficiency simply based on signs and symptoms. There's not a specific symptom horses present that points to Vitamin E deficiency specifically.
For example, there's Vitamin E deficient myopathy, which affects their muscles, and you'll see significant atrophy and weakness. The good news is that this can be reversed with Vitamin E supplementation.
Equine Motor Neuron disease is a neurological disease, meaning it affects the nerves. This occurs in horses who've been deficient for very long periods of time and is typically found once they start showing neurological symptoms. The symptoms could be anything from mild ataxia, not moving as correctly as they did before, up to showing very significant neurological symptoms.
These types of Vitamin E deficiency related diseases are one’s horses don't tend to fully recover from based on the research, although they can be stabilized.
There are even some disorders seen in very young horses with susceptible genetics. Not every young horse who has a Vitamin E deficiency in utero or during early life develop this, but if they have the type of genetics to predispose them to it, horses who are deficient during that critical time can have Equine Degenerative Myloencephalopathy. This is another disease they typically won’t fully recover from.
For this reason, supplementation of Vitamin E in broodmares is very important as well.
The good news is that unlike many other essential nutrients horses require, Vitamin E levels can be assessed and monitored with a blood test.
This is a great way to ensure horses aren’t becoming deficient before it causes potentially irreversible issues, and to monitor that they aren’t being over supplemented either.
Recommended Daily Vitamin E Levels and When to Supplement Vitamin E in Horses
The NRC, a council that looks at the current research and makes recommendations about the minimum amount of essential nutrients horses should be getting, recommends a minimum of 500 IU’s per day.
This recommendation is based off of a maintenance level (no exercise) for a 1,100-pound horse, which includes stallions and broodmares as well. This level recommended by the NRC is a bit low for most modern-day horses, however.
This is because once a horse’s exercise level increases, so does the recommended minimum for Vitamin E levels. An adult horse in moderate to heavy exercise should be getting at least 1,000 IU’s of Vitamin E a day.
The levels the NRC recommends don’t differentiate between naturally and synthetically sourced Vitamin E, however.
In situations where horses are deficient and you need to increase these levels quickly, natural resources are more bioavailable, more of a stable source, and overall, the best way to go.
But when that becomes challenging, such as in winter months, there are options for easily supplementing Vitamin E even in a horses regular feed or with a ration balancer.
One pound of Tribute’s Essential K, for example, is formulated to provide 1,000 IU’s. This is a good baseline (with a bit of a buffer) for most modern-day horses Vitamin E level requirements while still being far from levels that could be problematic for horses.
As previously mentioned, horses in higher levels of work are going to require higher levels of Vitamin E. If your horse is in heavier work, you might then feed two pounds a day of Essential K instead of one, which means you’re also doubling the Vitamin E levels. This is also ideal for horses with certain medical issues that need extra supplementation and Vitamin E anyways.
For full-intake feeds like Kalm N’ EZ, which is a feed for both calories and nutrients, it also has 1,000 IUs per day of Vitamin E—even for the minimum recommended feeding rate.
Vitamin E is a very safe nutrient overall, and while it’s possible to over supplement Vitamin E, clinical toxicity related to over supplementation of Vitamin E is rare.
10,000 IUs per day of Vitamin E is considered the maximum safe amount horses can consume. However, you might need to go up this high level for short periods of time for severely deficient horses, or horses with certain diseases, like those first diagnosed with EPM and those who are actively neurologic.
If your horse needs to be on high levels of Vitamin E for long periods of time in these certain circumstances, monitoring bloodwork is important as this can decrease the absorption of some other nutrients, specifically beta-carotene.
Ultimately, as long as horses Vitamin E levels stay in the mid-range, such as around that 4,000 to 5,000 IU’s per day, this is not going to cause any issues.
If you have any questions about your horse’s feeding program, please reach out to us for a free personalized equine feeding plan.
