Does Your Horse Need Vitamin E?
Here's the lowdown on this essential nutrient supplement.

What it is: A fat-soluble vitamin.

Why your horse needs it:

• To help prevent muscle problems, such as tying-up

• To boost his ability to fight off infectious diseases

• Possibly to improve reproductive performance.

• To avoid deficiency-related problems, including muscle and nervous-system disorders, and poor functioning of the immune system.

• As an antioxidant, Vitamin E travels through your horse's body, cleaning up damaging free-radicals, substances produced during normal metabolism that can cause tissue damage.

You need to supplement with it: If your horse doesn't have access to good pasture. Vitamin E is found in pasture grasses and legumes. Since 75 to 80 percent of the vitamin is lost in the cutting, drying, baling, and storage of hay, horses without pasture access are likely to need supplementation.

How to supply it:

• Feed at least 500 to 1,000 IU (international units) of vitamin E daily. Up to 6,000 IU may be recommended to overcome deficiencies, help with muscle problems, or strengthen your horse's immune system.

• There are various forms of vitamin E. In horse feeds and supplements, look for dl-alpha tocopheryl acetate, as it has good activity and better stability for storage than most other forms. (Note: 1 mg of dl-alpha tocopheryl acetate is equal to 1 IU of vitamin E.)

• Vitamin E is nontoxic, so oversupplementation isn't a concern.

• A caveat: Many supplements containing vitamin E also contain selenium. Because selenium can be toxic, make sure your horse doesn't get more than 3 mg of this mineral per day. If he needs extra vitamin E and is already receiving adequate selenium, look for a supplement that contains vitamin E alone.

Barb Crabbe, DVM, is an Oregon-based equine practitioner and frequent contributor to Horse & Rider.