Horse Vitamins and Supplements: Smart Choices for Owners

Walk into any feed store, and the supplement aisle alone can stop you in your tracks. There are pellets for hooves, powders for joints, liquids for gut health, and oils for coat shine. That’s before you’ve even gotten to the vitamins.

For most horse owners, the honest reaction is somewhere between curious and completely lost. The good news is that navigating this doesn’t have to be complicated, but it does require understanding one thing first: what your horse is missing.

Supplementation done well isn’t about buying more. It’s about filling the right gaps.

Why Forage-Based Diets Often Fall Short

Most horses eat hay, pasture, maybe a scoop or two of concentrate, and that’s generally a sensible approach. The problem is that forage is not consistent. Hay from one region or one growing season can be nutritionally very different from hay that looks nearly identical from somewhere else. Mineral content is heavily influenced by soil quality, and there’s no way to know what you’re dealing with just by looking at the bale.

Zinc, copper, vitamin E, and several B vitamins tend to be the most frequently undersupplied nutrients in forage-heavy diets. But it’s not always a simple case of what’s missing. Sometimes it’s about what’s interfering.

High iron levels in hay and pasture are more common than most owners realize, and excess iron actively competes with zinc and copper during absorption. A horse could be eating what looks like an adequate diet on paper and still end up functionally deficient in both.

This is exactly why thoughtful vitamin supplements for horses are often a necessary part of a well-managed feeding program. The goal is to address what forage and feed alone consistently fail to provide.

Key Vitamins and Minerals Worth Knowing

Knowing which nutrients matter, and why, makes it much easier to evaluate what your horse needs.

Vitamin E

Of all equine nutrients without regular access to fresh pasture, magnesium is often lacking. Magnesium is important for the proper function of muscle tissue, immune function, and

neurological health, so horses that are in hard work and/or don’t have enough turnout are at high risk of being low on this nutrient.

Prolonged deficiency of magnesium may be associated with equine motor neuron disease, a disease that can lead to severe disability or death; therefore, it is advisable to monitor this nutrient closely.

Vitamin A

Horses typically obtain vitamin A through the conversion of beta-carotene obtained from green pastures into retinol when they graze. Since hay does not contain much or any beta-carotene, the vitamin A content of hay will gradually diminish over time. Therefore, full daily intake is important for proper immune function, vision, and reproduction.

Vitamin D

Vitamin D works with calcium and phosphorus to maintain bone mineral density of the skeleton as well as skeletal health. Horses will make vitamin D by being out in the sun. Horses that are kept under artificial light or that live in an area with a lot of cloudy days during the winter may be at higher risk of insufficient vitamin D.

Trace Minerals

In the case of trace minerals such as copper, manganese, selenium, and zinc, the particulars are important.

Zinc contributes to good immune function, good hoof health, and good skin health. As a result, if your horse is deficient in zinc, then you may see problems with hoofs and skin before your horse develops other potential deficiencies.

Copper is needed to produce melanin, so if your horse is deficient in copper then you may see changes in coat colour (i.e., loss of copper can cause a copper-deficient horse to develop a pale out (white) appearance) before anything else.

Selenium is one of the harder trace minerals to manage because both deficiency and toxicities can cause very serious consequences. So, the precise amount of selenium you feed your horse is far more important than simply adding more selenium.

There is also a big difference between organic and inorganic trace minerals. Organic trace minerals are connected to amino acids, which can make them more bioavailable because they may be absorbed by the digestive system more efficiently.

This is important because in horses that are consuming high-iron forage, the presence of competing minerals may result in a reduced absorption of organic trace minerals.

The Case for a Comprehensive Mineral Supplement

Ration balancers and comprehensive mineral supplements exist to do one thing well: close the gap between what forage provides and its overall health needs, without loading unnecessary calories into the diet. That makes them a practical option for easy keepers, horses on hay-only programs, or any horse whose workload doesn’t justify large amounts of concentrate.

Mad Barn’s Omneity is an example of this type of supplement. It’s an all-in-one vitamin and mineral premix that includes organic trace minerals, a complete B-vitamin complex, biotin, and key vitamins including E and A.

It addresses the most common deficiencies found in forage-based diets in a single daily serving. According to Mad Barn, their research on Omneity points to real, measurable outcomes when it’s used to properly balance a diet that’s otherwise falling short.

In Mad Barn’s 16-week controlled field study published in early 2026, 16 mature Friesian geldings with cracked hooves and faded coats were split into two groups. One continued their existing diet, while the other received Omneity at 120 g per day alongside a zinc-copper supplement to offset high dietary iron in their forage.

Mad Barn reports that the supplemented group grew hooves 22% faster over the 71-day measurement period (3.77 cm versus 3.10 cm), with fewer cracks and more uniform new wall growth.

Both groups shared the same environment and management throughout, which makes the difference hard to attribute to anything other than the nutritional intervention.

Hoof Health

Many people consider hoof quality an issue associated with the services of a farrier, when in fact the hoof wall is composed of keratin (a type of protein) that depends upon adequate nutritional input to grow properly.

Methionine, cysteine, biotin, zinc, and copper are all part of the nutrition needed for proper hoof health. If any one of those nutrients is chronically deficient or lacking, it shows in the condition of the hoof.

Biotin supplementation at dosages of 15–25 mg per day has scientific support to help improve the quality and growth of hoof horn. This is especially for horses with compromised hooves.

Also, keep in mind that it takes approximately six months for a horse’s hoof wall to fully grow out from the coronet (top) to the ground. Therefore, owners who begin to address any nutritional inadequacies and expect to see tremendous results within a few weeks are setting themselves up for disappointment. The result will be seen eventually, but it takes time for healthy hooves to grow out.

Joint Health and Digestive Health

When considering joint health for horses experiencing high-impact workout loads or those that are older horses, it makes sense to consider joint health from a different perspective than just looking at general-purpose mineral supplements.

That’s because there are several beneficial ingredients to support the maintenance of cartilage integrity and joint fluid viscosity. This includes glucosamine, chondroitin sulfate, and hyaluronic acid, all of which have sufficient backing from published clinical data demonstrating efficacy.

The equine digestive system is quite sensitive, often overlooked when discussing supplementation. Horses evolved to graze continually in small amounts of forage throughout the day.

In contrast, feeding large meals at longer intervals can overload the digestive system, which can lead to decreased absorbable nutrient material being utilized by the horse. This may alter the horse’s behaviour as well as affect their performance.

During periods of stress, transport, or food transitions, probiotics and prebiotics can also be beneficial to maintaining a healthy hind gut and potentially reducing the likelihood of future digestive issues.

Putting It All Together

Get a forage analysis prior to any purchases. Understanding what is in your hay allows you to make more informed and targeted choices instead of randomly buying half the supplements you see on the store shelf. Once you understand the quality of your hay, using a high-quality vitamin and mineral supplement can help you to close the most common deficiencies in nutrition consistently and dependably.

This article is for informational purposes only and does not substitute for professional veterinary advice. If you are seeking advice, diagnosis, or treatment for your pet, please consult a veterinarian or qualified animal healthcare provider.