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by Casie Bazay

Understanding horse vitamins and minerals

Understanding horse vitamins and minerals

Vitamins and minerals, aka micronutrients, are not needed in large amounts by horses and therefore might be easy to overlook in the diet. However, these tiny but mighty nutrients are vital to a horse’s overall well-being. In fact, a deficiency in any one of them might mean the difference between a top performing horse and one that doesn’t quite make the cut. 

Horses grazing over a large area, as they evolved to do, can usually meet their vitamin and mineral needs by consuming a mixture of grasses and other types of plants. However, this isn’t the situation most of our horses live in today. And when you add the demands of training and performance, it’s easy to see why pasture or hay, alone, isn’t able to meet the vitamin and mineral needs of most horses. 

Fortunately, feed companies keep all of this in mind when designing their products. However, if you aren’t feeding the recommended amount of feed according to package directions, or if you’re just feeding a single ingredient such as oats or corn, your horse can still end up with deficiencies. These are the times when adding critical horse minerals or horse vitamin supplements may be warranted. 

Horse vitamins of importance

Vitamins, classified as either water-soluble or fat-soluble, help to regulate many metabolic processes in the horse’s body.  While some vitamins are produced by the horse, others must be provided in the feed they consume. 

Horses require vitamins A, B, C, D, E, and K to stay healthy, and while these vitamins are only needed in very small amounts, vitamin deficiencies can lead to health problems. 

Vitamins A, D, E and K are considered fat-soluble vitamins, meaning that they are processed and stored in a similar way to fat, while vitamins B and C are water-soluble and not readily stored in the body.

Vitamin A is found in fresh grass and good quality hay and horses are able to store it in their liver for future use (such as during the winter when green grass isn’t available). 


Vitamin B is actually a complex of several vitamins (including niacin, thiamine, biotin, cobalamin, etc.), all produced in the horse’s hindgut by healthy gut microbes. 

Vitamin C is also formed in the horse’s body and helps to protect cells from damaging free radicals. 

Vitamin D is another one that is produced by the horse, but only when they are exposed to sunlight for at least 4-6 hours a day. It is also found in sun-cured hay. 

Vitamin E, which is used to describe a group of compounds known as tocopherols and tocotrienols, provides important antioxidant qualities and is found in grass and fresh hay. 

Vitamin K is manufactured in the horse’s hindgut and is also found in grass and hay. 

As long as a horse has good pasture or hay, or is on a high-quality complete feed, horse owners don’t generally need to worry about vitamins. The only exceptions would be in the case of older or sick horses, or elite performance horses who may lose their ability to produce adequate amounts of vitamins B, K, and C and can often benefit from supplementation. Older or ill horses and even those in hard work may also benefit from supplemental vitamin E

Dr. Amanda Bradbery, FullBucket’s senior equine nutritionist says, “Vitamin deficiencies are not often a concern when horses are receiving high-quality forage or commercially formulated concentrate feeds.  However, during high levels of performance and exercise, hindgut microbial populations often cannot keep up with the added demand for B-complex vitamins and vitamin K, which could result in a deficiency that would present as fatigue or reduced performance potential. Because B vitamins are water-soluble and not stored in the body’s reserves, they are safe to supplement with no risk of toxicity.”


Macro and trace minerals for horses

Both major (macro) and trace minerals need to be provided in the horse’s diet, and as one might guess, macrominerals are needed in higher amounts than trace minerals (microminerals), though both are of equal importance in equine nutrition. The essential macrominerals include:

  • Calcium (Ca)
  • Phosphorus (P)
  • Magnesium (Mg)
  • Sodium (Na)
  • Chloride (Cl)
  • Potassium (K)
  • Sulfur (S)

With macrominerals, several ratios are important, one being calcium to phosphorus, which should ideally be at 2:1, calcium to phosphorus. If phosphorus is higher than calcium in the diet (which can happen with high grain/low forage diets), horses may develop bone problems. Another important ratio deals with calcium and magnesium, which should ideally be kept between 2.5:1 to 3:1, calcium to magnesium. 

Dr. Bradbery explains, “Inverted ratios of macrominerals can have many different negative implications on the horse’s skeleton, muscle function, and electrolyte balance.  The ratios are often considered a more important factor than the concentrations of minerals themselves.

In performance horses, electrolytes are of utmost importance and include the macrominerals: Na, K, Cl, Ca, and Mg.  Electrolytes are macrominerals that when dissolved in body fluids, carry a positive or negative charge known as an ion.  These are incredibly important for maintaining normal muscle function and fluid balance during exercise.  Again, ratios are an important consideration with Na:K:Cl recommended at 2:1:4 to maintain normal electrolyte balances for exercise.”

Since most feeds and forages don’t contain enough sodium or chloride for performance horses, it’s important that horses always be supplemented with a free-choice salt block. 

The essential trace minerals for horses include:

  • Iron (Fe)
  • Zinc (Zn)
  • Copper (Cu)
  • Selenium (Se)
  • Manganese (Mn)
  • Iodine (I)
  • Cobalt (Co)

Many trace minerals can be found in grass, hay, and feeds, but the trace minerals most likely to be deficient in the horse’s diet include zinc and copper. 

The bioavailability of vitamin and mineral supplements for horses is a key consideration 

Again, healthy horses consuming plenty of good pasture or hay are already consuming many vitamins and minerals, but most still need additional micronutrients in the form of a feed, ration balancer, or supplement (especially in the case of minerals). 

However, not all vitamins and minerals added to feeds or supplements are created equally. In fact, many vitamins and minerals occur in several forms, some cheaper to obtain than others. Unfortunately, not all forms are highly digestible by the horse. With minerals, the ones that are most easily digestible (chelates and proteinates) are also the most expensive. 

Chelation is a chemical process in which a mineral is combined with a mixture of amino acids and peptides (producing what are known as chelates). Chelated minerals are more digestible, or bioavailable (able to be absorbed and used by the horse) than non chelated forms. You may also hear proteinates or chelates described as organic minerals as opposed to inorganic minerals (those not bound to amino acids). 

Dr. Bradbery agrees that chelation is a key consideration, especially when it comes to trace minerals in the horse’s diet. “Trace minerals, although supplemented in small concentrations, play important roles in normal bone/joint function, metabolism, muscle function, etc.  While the bioavailability of macrominerals is less impacted by supplemental form, the bioavailability of trace minerals is greatly improved when supplemented in its organic form (amino acid complex or proteinate) compared to inorganic forms.”

When looking at feeds or supplements for your horse, it’s best to spend a little more and find one with organic or chelated minerals. 

Another way to boost the bioavailability of any nutrient, including vitamins and minerals, is supplementing your feeding program with a high-quality digestive product like Athletic Formula. This equine supplement is designed to improve feed digestion and nutrient utilization in order to maximize immune and gut function in horses, while also offering bioavailable (organic) minerals and vitamins. 

Made with eight strains of probiotics, digestive enzymes, biotin, L-Glutamine, and several essential vitamins and minerals (including organic zinc and copper), Athletic Formula offers the complete package to help keep your performance horse at the top of his game. 

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