Mineral Needs and Deficiencies in Horses

Horses require six key classes of nutrients in their diet. One of these is minerals – they cannot be synthesized by the horse, therefore they must be adequately provided in the diet.

Meeting a horse’s mineral requirements is crucial to their health and well-being. They play an important role in a variety of physiological processes such as enzyme reactions, metabolism, and electrolyte balance, to list a few examples. Many horses will have prolonged mineral deficiency for years without showing clinical symptoms; therefore knowing how to meet these requirements is important for equine well-being.

What minerals do horses require?

The minerals that a horse requires can be divided into two categories: macrominerals and microminerals, which are also referred to as trace minerals. The macrominerals are needed in more significant amounts, often in grams; the micro or trace minerals are required in smaller amounts, often in milligrams.

Scroll to continue with content

Macrominerals required:
Calcium
Phosphorus
Potassium
Chloride
Sodium

Microminerals required:
Copper
Selenium
Zinc
Iron
Manganese
Iodine
Cobalt

The Nutrient Requirements of Horses (2007) details the recommended amounts for supplementing the various minerals. These amounts are based on our current knowledge from research that has been done both in horses and other species. Research has clearly shown health benefits when an equine diet is meeting the mineral supplementation amounts recommended in the NRC.

Like other nutrients, the amount a horse requires will vary based on a variety of factors such as age, workload, physiological state, weight, etc. The NRC details mineral requirements for horses of various weights and workloads.

Mineral deficiency symptoms

Unfortunately, in equine nutrition it can be difficult to notice a mineral deficiency, and often when symptoms do present, the deficiency has been a prolonged issue. An important reminder is that just because you can’t see a mineral deficiency doesn’t mean one doesn’t exist in your horse’s diet. Additionally, some deficiency symptoms may not be obvious – such as poor performance or poor reproductive efficiency.

Some clinical symptoms that are often attributed to a mineral deficiency include:

Improper cartilage development
Poor ability to gain/maintain muscle
Weight loss
Dull coat
Weak hooves
Recurring gut issues
Brittle bones
Sun-bleached coat
Hyperparathyroidism (Big Head disease)
Pica appetite (eating non-food items)
Behavioural changes
Compromised immune response
Osteochondrosis in young horses

The above list is not comprehensive, and if you have any concerns with health issues, your veterinarian should be contacted.

Detecting a mineral deficiency

As mentioned above, detecting a mineral deficiency can be difficult, and if you are noticing symptoms then it is likely that this has been a prolonged deficiency that is now causing serious health problems. There are three main ways that mineral deficiencies can be detected; however, not all are equally effective.

1) Hay Testing and Ration Balancing

Testing your hay and having your horse’s ration balanced is a reliable way to ensure your horse does not have any mineral deficiencies. The mineral content of the various feeds and supplements your horse eats would be detailed in the guaranteed analysis. Then when you have your hay analyzed, a nutritionist can compile that information and ensure it is meeting the requirements outlined in the NRC. With this method, your nutritionist can also calculate mineral ratios.

For mineral supplementation, it is crucial to meet the required amount, but the minerals must also be supplied in the correct ratios. One of the most discussed ratios is calcium-to-phosphorus. The ideal is about 2:1, therefore, not only do you need to meet the required amounts in the diet, but the minerals have to be supplied in adequate proportions. Ensuring balance is important for mineral absorption and function, as there are complex interactions between minerals.

2) Hair Samples

Using hair sampling to determine mineral status is a test that is gaining popularity; however, the research does not illustrate reliability. Additionally, hair analysis provides a picture of the mineral status over the previous months and may not accurately represent the current mineral status. Another drawback to the practice is that there are no well-established reference ranges, so it can be difficult to interpret the test results.

A study published in 2022 investigated the efficacy of hair analyses to assess mineral intake in horses. The research involved comparing mineral analysis results in equine hair between three commercial laboratories. The authors concluded that the results were not consistent, likely due to poorly established reference ranges. For example, selenium was reported to be at an inadequate content for all of the horses by two of the laboratories but was deemed adequate by the third. Therefore, this recent publication concluded that hair analysis is not a reliable method to assess mineral intake in horses.

3) Blood Samples

When a blood sample is taken, it represents a moment in time. The results illustrate the mineral content of the bloodstream at that moment. The mineral content in the bloodstream is impacted by a variety of factors including exercise and time passed since the last meal. Therefore, it has been concluded that this is not an effective test in determining the mineral status of a horse.

There is research supporting the use of this method for investigating vitamin E and selenium status, but it has not been deemed reliable for other minerals that the horse has a requirement for.

Another issue with relying on blood sampling is that many of the minerals are controlled by the body, and at the end of the day, the body is good at maintaining homeostasis. For example, when calcium is low in the body, it will appear normal in the blood, as the horse will mobilize calcium from their bone stores in order to maintain adequate levels in the blood.

Preventing deficiency

Overall, the best way to prevent deficiency and determine if your horse is receiving adequate minerals in the diet is through a forage analysis and assessing their feed and supplement intake. If you suspect mineral deficiency or are attempting to address mineral deficiency symptoms by loading up on a joint supplement, you are likely going to run into further problems. Investing in a yearly hay analysis and having the diet balanced by an equine nutritionist can prevent significant problems if there is an underlying deficiency.