Trace minerals are only needed in very small amounts in a horse’s diet. Think milligrams! Despite this, however, the majority of horses still receive too much energy and protein and not enough trace minerals from their diet.

Deficiencies in key minerals over a long period of time can result in a plethora of problems with hoof quality, coat condition, digestion and can also affect the athletic performance of your horse.

This issue stems from the fact that complete feeds are often not well-fortified and are meant to be fed at a rate of 3-5 kg (7-11 lb) per day. Feeding less than this means that the levels of trace minerals that your horse is actually receiving are far below requirements.

Zinc, copper, selenium, manganese, cobalt and iodine are some of the most important trace minerals in equine nutrition. Knowing the basic requirements of each will help ensure that your horse consumes the right amount that it can’t obtain from forage alone.

To prevent deficiencies in your horse’s diet, it is recommended to feed a ration balancer like Mad Barn’s Omneity equine supplement in either premix or pellet form. Omneity is a complete vitamin and mineral formula for your horse that has been expertly formulated to provide everything needed to balance a forage-only diet.

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Zinc and Copper

These two trace minerals have similar roles in the horse’s body when it comes to the maintenance and growth of connective tissue and melanin. Proper intake of both zinc and copper is imperative for growing and mature horses, but what is even more important is the balance or ratio of the two.

Horses must consume copper and zinc in proper amounts so that one mineral doesn’t out-compete the other for absorption from the gut. A simple way to monitor this is to keep the Zinc:Copper ratio to between 4:1 & 3:1.

Other trace minerals may be affected as well. For example, excessively high copper intake has the potential to reduce the absorption and utilization of selenium and iron.

Providing adequate amounts of copper and zinc may not be possible when feeding forage alone, and so feeding a well-fortified vitamin and mineral supplement is necessary.

The recommended requirements for a 500 kg (1100 lb), mature horse at maintenance consuming 2% of their body weight in dry matter is 100-120 mg of copper per day, and 400-500 mg of zinc per day.


Iron is an important trace mineral for the functioning of hemoglobin and myoglobin, which are proteins that carry oxygen throughout the body.

Fortunately, iron deficiencies are very rare in horses due to the sheer amount of iron that is usually present in water, forage and most feeds. In fact, our recent review of over 6,500 equine diets found that 99.5% of horses exceed their iron requirements.

Since excess iron is a much more common problem in horses, antagonistic relationships with other minerals like copper, zinc and manganese are of higher importance. For example, high iron intake is known to negatively impact the absorption of dietary zinc and copper.

In addition, free, ionized iron acts as an oxidant, which increases oxidative stress and inflammation. The chronic inflammation caused by these excess free radicals in the body are thought to be implicated in the development of insulin resistance in mammals. [2]

Generally, only horses that experience severe blood loss, perhaps through a bleeding ulcer, chronic inflammation or heavy worm load, would be ones to watch out for and perhaps need additional iron in their diet.

The horse’s recommended daily requirement of iron is 400 mg.

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Selenium is a trace mineral component of