Understanding Mineral Supplementation in Equine Diets

Horses need a variety of minerals in their diet to support basic system function and overall health. Find out how to be sure your horse is getting them.
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Be sure to test your pasture’s nutritional content because your horse might get some essential minerals from grass. | iStock

Horses need a variety of minerals to support their daily nutritional requirements. These minerals play important roles in the body, from providing antioxidants to comprising key elements of bone. Without the right minerals, horses can develop health issues such as skin and coat problems or lack of muscle development. Ensuring your horse’s ration adequately provides him the essential minerals in the right amounts is imperative to his health and well-being.

How to Know if a Horse is Getting Enough Minerals

Accurately evaluating your horse’s mineral status is important because it can take many months for the health issues that arise from improper supplementation to become apparent. “Given that it isn’t possible to look at a horse and know whether you are providing the right amount of minerals just based upon the horse’s appearance until deficiencies or toxicities are pretty severe, the best approach is to know what your horse requires and determine if what you are feeding it meets the requirements,” says Brian Nielsen, PhD, MS, PAS, Dipl. ACAN, animal science professor at Michigan State University, in East Lansing.

The best way to determine your horse’s mineral needs is to have a nutritionist complete a full dietary evaluation, says Shannon Pratt-Phillips, MS, PhD, PAS, a professor in the Department of Animal Science at North Carolina State University, in Raleigh. First, obtain a hay analysis; because forage is the base of your horse’s diet, evaluating the quality of his hay will allow you to fill in the remaining mineral gaps with a concentrate or high-quality ration balancer. “Unfortunately, other tests, like hair or blood, are not very useful for measuring mineral status in the horse, so analyzing the full diet is the best way to ensure that your horse is meeting its needs,” she says.

Ideal Mineral Ratios in Horse Diets

Amounts of minerals are important when meeting your horse’s nutrient requirements, but don’t forget to consider mineral interactions. “When one mineral can affect the absorption of another mineral, we might need to establish a ratio to ensure that a particular mineral is not fed in amounts that might inhibit the absorption of another, even if the other mineral is fed in the correct amounts,” says Pratt-Phillips.

The most frequently discussed mineral ratio in equine nutrition is calcium (Ca) to phosphorus (P). “While many horse owners are taught that a ratio of 2:1 (2 parts Ca to 1 part P) or 1.5:1 is the ratio for which we should strive, it really isn’t critical that it is precisely that ratio,” says Nielsen. “As long as there is more available calcium in the diet than there is available phosphorus, there are typically no concerns. By contrast, a ratio of 1 part calcium to 1.2 parts phosphorus would be a real concern.”

A skewed ratio can cause the body to sense a calcium deficiency, even if the amount in the diet is adequate. “When there is a perceived calcium deficiency, there is a release of parathyroid hormone,” says Nielsen. “The result is calcium being released from bone in order to maintain blood calcium. Doing so can result in the condition known as nutritional secondary hyperparathyroidism (also known as big head disease) in which the bone is weakened.”

In addition to calcium and phosphorus, zinc (Zn) to copper (Cu) and iron (Fe) to copper to zinc to manganese (Mn) are important ratios to consider. “There is no published scientific research that supports the claims for Zn:Cu or Fe:Cu:Zn:Mn. Rather, it is just important that you are meeting the requirements, and it is also wise to avoid over supplementing minerals,” says Nielsen.

“I would be very wary of increasing other minerals simply to try to achieve some kind of ‘ratio’—for example, if iron is too high, we shouldn’t try to feed more copper or zinc to accommodate for that,” says Pratt-Phillips. “Research has shown that over supplementing minerals winds up in waste and, ultimately, in groundwater, and could be bad for the environment.”

Knowing When to Add Minerals to Your Horse’s Diet

The National Research Council’s (NRC) Nutrient Requirements of Horses, published in 2007, provides recommended intake levels of the necessary minerals based on your horse’s body weight and workload. “It is important to know the nutrient composition of what your horse is eating from all parts of their diet—that includes from forage, concentrates, and supplements,” says Nielsen. “It is easy to have hay analyzed for nutrient composition, and that is the only way to know what it provides.”

Many horse owners who receive different hay regularly might not invest in the analysis. “I would argue for even that one point in time, it is worth investing the extra $20-40 to get the hay analyzed to check the mineral status in the hay,” says Pratt-Phillips.

If your horse’s diet is primarily hay with an additional concentrate and/or supplements, again, a complete hay analysis will provide quality information for your nutritionist to help you develop a balanced diet for your horse. If you horse consumes pasture, evaluating the mineral content can be a bit more challenging. Nielsen suggests consulting with a local extension agent to find out if there are any known soil deficiencies in the area (such as selenium).

By calculating the total amount of minerals your horse consumes and comparing it to what the Nutrient Requirements say he needs, you can determine if your horse’s diet is sufficient.

Available Mineral Sources for Horses

Minerals included in your horse’s diet can be offered in organic or inorganic form. “Technically, in chemistry, ‘organic’ refers to being carbon-based, this meaning carbon is part of the molecule,” says Nielsen. “However, in popular culture, organic is often used to signify ‘natural’ and is a term that is widely used when marketing, as people believe it is better—rarely is there any evidence that such is the case. Ironically, with minerals, the inorganic tends to be natural, and the organic minerals tend to be synthesized or manufactured.”

A horse’s mineral requirements are based on his ability to digest and absorb them, so it is important to understand the differences in bioavailability between sources. “Organic sources of minerals are likely more bioavailable, so the horse may actually need less of them,” says Pratt-Phillips. “A good nutritionist will be able to pick out some of these ingredients in feed tags, and this could affect how you interpret a dietary analysis.”

Take-Home Message

Ensuring your horse receives appropriate amounts and types of minerals is a key consideration when developing a balanced diet for your horse. Both over- and undersupplementing certain nutrients can cause serious health problems, but clinical signs might not show up for months. Analyzing hay and consulting a qualified equine nutritionist to review your horse’s mineral intake can help you ensure your horse receives the correct nutrition from his diet.

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Madeline Boast completed her master’s in Equine Nutrition at the University of Guelph and started an independent nutrition company known as Balanced Bay. She has worked with a variety of equids—from Miniature Ponies to competing Thoroughbreds. Boast designs customized balanced nutrition plans that prioritize equine well-being, both for optimal performance and solving complex nutritional issues and everything between. 

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