Does My Horse Need Vitamin B Supplements?

A molecule of Biotin or Vitamin B7

'm not going to answer this question. Why? I think it is very important for horse owners to make reasonable decisions about caring for their animals based on sound information. So instead of telling you what I would do, what other people do, or even what other people say you should do, I’m going to give you the information you will need in order to decide whether you should give your horse vitamin B supplements.

Let’s start with the basics of B vitamins.

The B vitamins (along with Vitamin C) fit into a class of vitamins that are called water-soluble. Water-soluble essentially means that the vitamin is not stored in the body, but is excreted in urine and feces when there is more than is needed by your horse. There are some minor exceptions to this rule, but they are not important for this basic overview.

B vitamins play important roles in the metabolic functions of virtually every cell in a horse’s body. There are a total of eight B vitamins. When they are grouped together in a supplement, they are called Vitamin B Complex. They have each been called different things over the years since first being identified, but today they are most commonly referred to by their names. They are:

• Thiamine or Vitamin B1
• Riboflavin or Vitamin B2
• Niacin or Vitamin B3
• Pantothenic Acid or Vitamin B5
• Pyridoxine or Vitamin B6
• Biotin or Vitamin B7
• Folic Acid or Vitamin B9
• Cobalamin or Vitamin B12

Now, if you ever read the ingredients on a horse supplement package, you will probably see one or more of the B vitamins listed, with biotin being a main component of many hoof supplements, and thiamine being prevalent in “calming” supplements. And even though biotin is very important in, for example, the production of keratin (an important material in hoof building), and thiamine is thought to increase feelings of well-being in a horse, the question remains: does giving supplemental B vitamins offer your horse any real benefits?

Again, I hope you will be able to make that decision on your own by the time you finish reading this. Understanding where a horse naturally gets B vitamins will be important in that decision.

So where do B vitamins come from? All eight of the B vitamins are produced by the microflora in a horse’s hind gut. This is a kind of symbiotic relationship where the horse provides food to the beneficial microbes within its digestive system in the form of fiber. In return, the microbes then (in addition to several other important functions) produce B vitamins critical to the horse. In addition, a horse that is on a quality forage diet receives more B vitamins from plant matter, including fresh grass, all types of hay and even grain. The only exception is B12, which is not found in plants, so is only available to the horse via production by the gut’s microflora. In addition, there is strong evidence that a horse can synthesize niacin from the amino acid tryptophan, which is also abundant in quality forage diets. It is therefore widely agreed that a healthy horse receives more than sufficient B vitamins from the combination of gut microflora, feed and internal synthesis.

(Here’s where I unfortunately cannot avoid mentioning what some people might tell you to do, because I think it makes some sense.) There are circumstances under which some professionals would recommend the use of B vitamin supplements, the main two being, 1) when a horse is on a diet of very poor forage, or 2) when gut health, and hence the vibrancy of the microbial community has been compromised by heavy use of antibiotics or feeding too much starch. In these two cases, however, it seems the supplementation would act purely as a stopgap until the horse’s diet is improved and/or the gut microflora return to a healthy state.

So, a brief summary:

1. B vitamins are water-soluble and cannot be stored by a horse for later use. If not used, they are excreted quite rapidly in the urine and feces, usually within a day or so.
2. Except for B12, which is available solely from a horse’s gut microflora, all the B vitamins are naturally available in good amounts from at least two sources: quality forage and production by the microbes in the horse’s gut.
3. Very little research has been done on the required amounts of B vitamins in a horse’s diet.
4. Signs of B vitamin deficiency are rarely identified in horses, and in the case of some of the B vitamins, signs of deficiency cannot even be described.

Have you made your decision about B vitamin supplements for your horse? If not, let me ask one final question:

If your gas tank already has gas in it, will adding more make your car go any faster?

​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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