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Horse Health: Vitamins and Minerals

Learn how to make the most of what little we really know about vitamin and mineral needs for your horse.

Photo by Janis Tremper

There's a sale on "Super Steed" vitamins at your local feed store. It's almost half the price of the daily scoop of "Performance Lift" that you usually give your horse. What should you do? Is one vitamin supplement really that much better than the other?

That's a great question. Chances are even your veterinarian doesn't know. In fact, if truth be told, solid science about vitamin and mineral supplementation for horses is in its infancy. You need more than price comparisons and marketing claims for help making a decision about which supplement to choose.

I'll explain what role vitamins and minerals play in maintaining your horse's health, and how basic nutrient requirements are determined. (You may be surprised to learn how little we really know about your horse's needs.) Then, I'll fill you in on what we do know about some specific (and important) vitamins and minerals. Finally, I'll help you decide what supplementation might really be beneficial for your horse, so you can decide what product to choose.

Vitamins and Minerals 101
A vitamin is an organic (contains carbon atoms) compound that's essential for normal growth and metabolism, and is required in small quantities in the diet because it can't be synthesized or produced by the organism (your horse). Vitamins have diverse jobs when it comes to keeping your horse's body functioning. For example, vitamin D aids in absorption of calcium from your horse's small intestine, while vitamin E scavenges for damaging "free radicals," and helps to protect the body's cell membranes.


In contrast to vitamins, minerals have a definition separate from their role in body functioning. A mineral is an inorganic (does not contain carbon atoms) substance that's stable at room temperature and has an ordered arrangement of atoms; in simpler terms, it's a solid crystal. Almost 5,000 minerals are known to exist, and of those, a relatively small number are required in the diet of your horse to make sure his body functions the way it should. Certain minerals are critical, such as potassium, which is key to keeping your horse's muscles contracting—and his heart pumping!

What About Requirements?
A great deal remains unknown about specific requirements for many vitamins and minerals. Most recommendations are based on the estimates published by the National Research Council of the National Acadamies, and come from review of available data by experts on their panel. It's important to realize that these requirements aren't necessarily determined by specific studies—so recommendations may change as we learn more. The most recent NRC requirement estimates were published in 2007.

The most difficult thing to decide is whether your horse needs supplementation at all, and if so, how much? If your healthy horse with a moderate work schedule has turn-out time and a diet of good-quality hay, chances are his vitamin and mineral needs are met already. Toxicity is rare, which is why the most common recommendation you'll hear is to "provide a balanced vitamin and mineral supplement" as an insurance policy against deficiency. The guide below will help you understand why your horse needs specific vitamins and minerals, where he gets them, and when you might need to add something extra to his daily ration.

Vitamin Guide
Vitamins can be divided into two groups: fat-soluble (dissolve in fat) and water-soluble (dissolve in water). Fat-soluble vitamins include A, D, E, and K, while water-soluble vitamins include vitamin C and the B vitamin group (thiamin or B1, riboflavin, B12, niacin, folacin, pantothenic acid, biotin, and B6).

The B vitamins are considered in a group because they all have a similar function of assisting with cell metabolism. Historically, they were believed to be a single vitamin, until it was discovered that they all have a slightly different chemical composition. For practical purposes, an important distinction is that fat-soluble vitamins have potential for toxicity, while water-soluble vitamins do not. Here is a guide to what we do (and don't) know about these vitamins.

Vitamin A
What it does:
Vitamin A is crucial for proper function of proteins necessary for vision. It plays a role in differentiation of cells during growth, is important for proper muscle function, and helps keep mucous membranes healthy. It's also involved with reproductive function.

Where it comes from: Beta-carotene, which is converted into vitamin A, is present in fresh pasture and hay. Your horse will store it in his liver for several months, even after it's no longer available, which will help protect him from deficiency for several months when pasture is no longer available or hay quality suffers.

Needed by 1,100-pound horse: Approximately 15,000 IU per day (1mg of B-carotene is equal to approximately 400 IU of vitamin A).

When he might need more: Vitamin A supplementation is rarely necessary unless your horse has no access to green forage. If you have fertility problems with your mare or if she's pregnant but lacks access to pasture or good, green hay, vitamin A supplementation might be recommended.

B Vitamins
What they do: Vitamins in this group are all involved with metabolism of carbohydrates, proteins, and fats. They help your horse produce the energy he needs to live from the food he eats.

Where they come from: B vitamins are produced by the bacteria that live in your horse's large intestine. They're also found in good-quality pasture and hay.

Needed by 1,100-pound horse: Most, if not all, of your horse's B vitamin needs are met by production in his own body, and the remaining amount he needs is usually met from hay or pasture. Specific levels for supplementation haven't been established. When he might need more: If your horse has poor-quality hooves, supplementation with 20mg per day of biotin may help. B vitamins are believed to have a calming effect, and might be recommended for a nervous horse.

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