The Basics of Vitamins for Horses

In the world of horse nutrition, the word “vitamin” is used very broadly (and often incorrectly) to describe many types of nutritional components, ranging from amino acids to minerals to herbal supplements. There is nothing inherently wrong with that I suppose, but as a responsible horse owner you should understand what vitamins actually are, where they come from, and why they are important to your horse’s health. Here is an overview that should help you along your path to better understanding your horse's nutritional requirements.

There are two classes of vitamins: water-soluble and fat-soluble. Very simply put, water-soluble vitamins are not stored in a horse’s body tissue and are excreted through urine and feces when not used, while fat-soluble vitamins are stored in certain tissues in the horse and are retrieved and used as needed. Let’s talk about the vitamins in each of these groups.

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Water-soluble Vitamins

​The water-soluble vitamins include the B complex vitamins and vitamin C.

I have written in some detail about the B complex vitamins in a previous post, which would be helpful to review. But very briefly, all eight of the B vitamins are produced by the micro flora in a horse’s hind gut, and all but one of these eight can also be found in quality forage, including fresh grass, quality hay, and even grains. B vitamins play important roles in the metabolic functions of virtually every cell in a horse’s body.

Vitamins C can be found to some degree in quality feeds, but most importantly it is synthesized from glucose in a horse’s liver. A healthy horse should be producing adequate amounts of vitamin C with this process. Vitamin C is a critical anti-oxidant, helping to prevent the destruction of cells.

Fat-soluble Vitamins

The fat-soluble vitamins are vitamins A, D, E and K

Vitamin A is found in fresh forages and in good quality hay. The amount of vitamin A is diminished when these forages are processed or are of poor quality. Most horses on a good-quality forage ration will be receiving adequate amounts of vitamin A in their diets. Vitamin A is important for, among other things, healthy eyesight, reproductive health, and a strong immune system.

Vitamin D is synthesized by the horse with the help of sunlight. A healthy horse living under normal conditions should be synthesizing adequate vitamin D for its needs. Vitamin D is important at helping the horse absorb and keep certain minerals at consistent levels, especially calcium.

Vitamin E is found in adequate levels for a horse in quality green forages, especially fresh grasses and quality, unprocessed hays. Vitamin E is an important anti-oxidant, helping cells maintain their structure. Horse that are on very poor quality forage can sometimes be deficient in Vitamin E, but improving the quality of the ration will generally solve this problem.
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Like the B vitamins, vitamin K is synthesized by the microbes in the hind gut of a healthy horse. Vitamin K is critical for blood clotting, bone metabolism and heart health.
 
So there you have it. As you can see, a healthy horse that is fed a good-quality forage ration should be receiving sufficient vitamins for its needs. If you suspect your horse has health issues related to vitamins, don’t go it alone. Just throwing “vitamins” at a horse will rarely have any beneficial effect. Talk to your veterinarian or nutritionist to look for the actual cause of the problem.
 
As always, this article is not an attempt to diagnose or prescribe treatment for any particular equine health problem. If you suspect your horse is suffering from any health problem, consult your veterinary professional for testing, diagnosis and treatment.

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