When Freedom was tested for Lyme, my vet also suggested testing his vitamin E levels. Horses that are deficient in vitamin E can have muscle soreness and long-term deficiency can cause neurological dysfunction.

Horses get vitamin E from fresh, green pasture. Freedom is out on pasture but we don’t have that much, especially at this time of the year. He’s also on a high fat diet and there’s been some research that shows animals on high fat diets have an increased need for vitamin E.

Grains typically have some vitamin E added, but not all that much. For example, the ration balancer that I feed Freedom has 500 IU of vitamin E per pound; the recommended daily amount is 2000 IU per day to prevent neurological dysfunction.

Freedom’s blood work shows that he is slightly deficient, with a level of slightly under 1400.

So, while it’s not a huge deficiency, I’m now supplementing his vitamin E intake because this is a case where preventive measures work better than treatment. At least with vitamin E toxicity isn’t really an issue so if you feed a bit too much, it’s not a problem.

Here’s the catch: you need to feed vitamin E that’s derived from natural, rather than synthetic sources. Synthetic vitamin E has significantly lower biological activity than natural vitamin E. Other studies indicate that the body may at worse, just excrete synthetic E and at best, not retain it as long as natural E.

You can tell the difference between synthetic and natural E by the ingredients. The difference is subtle:

Natural = d alpha-tocopherol
Synthetic = dl alpha-tocopheryl

When I started to look at equine supplements I was actually quite surprised by how many of the E supplements use the synthetic version. The big giveaway is price: supplements with natural vitamin E are far more expensive than those made with the synthetic vitamin. In the end, I bought the supplements from Costco.

Vitamin E is also a vitamin that needs to be stored carefully in a dark, cool location. Exposure to heat and light can cause the potency of the vitamin to degrade.

There is very little vitamin E added to most bagged horse feeds. What little there is can be destroyed by storage, heat, age, and sunlight – and the same is true of the vitamin E in your supplement bottles. Fresh vitamin E supplements, properly stored (in a dark bottle in a cool place), may help your horse. Old or inappropriately-stored vitamin E supplements may have no effect whatsoever.

What about Selenium?

You will notice if you look through supplement catalogs that many Vitamin E supplements are co-packaged with selenium. Selenium is a trace mineral that helps with the absorption of vitamin E. In many parts of the US the soil has very low — or non existent — levels of Selenium so it must be provided via a supplement. The tricky thing about Selenium is that it is toxic in large doses (remember the polo ponies that died in Palm Beach? That was caused by an improperly compounded supplement that contained toxic levels of Selenium).

The dose for an adult horse is about 1-3% of body weight. There is still discussion in the scientific community as to whether horses in heavy work require more selenium than those in light work.

So, before feeding a vitamin E/Selenium supplement it’s a good idea to find out how much is provided in your feed and how much is present in your soil.