Sick horses need special support, and in such cases, supplementation with individual nutrients can be beneficial. It is important to note, however, that trace and bulk elements can interact with each other and may limit the absorption capacity of other minerals.

Nutrient Deficiency Triggers Gastric Issues

Nutrient deficits, as can occur during high levels of physical exertion such as intense training, may be exacerbated by an inadequate mineral supply. If the horse is deficient in magnesium, manganese, and selenium, it can lead to spasms near the pylorus (stomach exit), disrupting the passage of food from the stomach. The result is sustained tension in the stomach and abnormal fermentation.

Calcium and Phosphorus

Calcium and phosphorus are essential components of the skeleton and are responsible for bone stability. They are also involved in numerous metabolic processes. Calcium and phosphorus act as antagonists and influence each other’s absorption. The optimal ratio of these two macrominerals is 2:1. Calcium levels in hay can vary greatly, so supplementation is often necessary.

Calcium has the ability to buffer or neutralize stomach acid, making it suitable for horses with excess gastric acid.

However, an excess of calcium can lead to a magnesium deficiency. The ratio of calcium to magnesium should be approximately 2:1 to 3:1.

Magnesium

Horses suffering from magnesium deficiency often appear jumpy; this is due to overreactions in nerve signal transmission. Especially in stressed horses, magnesium supplementation can be useful, as stress is one of the main triggers for gastric ulcers, colic, and diarrhea. Other symptoms of magnesium deficiency include general fatigue, unwillingness to work, circulatory problems, and swollen legs.

In most cases, the magnesium requirement is covered through forage. However, if pastures are very monoculturally planted, magnesium should be supplemented.

Equine 74 Gastric has a high content of calcium and magnesium and features a unique sponge-like structure that provides 2.5 times the acid buffering capacity compared to supplements made from limestone.

Sodium 

Sodium is responsible for osmotic pressure and the regulation of acid-base and water balance. Like potassium, magnesium, and calcium, sodium is a cation (positively charged) and therefore has an alkaline effect. It can buffer acids by absorbing negatively charged anions from gastric acid and maintaining the pH balance of the stomach.

Zinc

The trace element zinc is known for its regenerative effects on skin and mucous membranes, as well as coat and hooves. It is also indispensable for a functioning immune system. Symptoms such as a dull coat may occur with zinc deficiency. Especially during coat change, when nutrient demand is increased, horses can benefit from zinc supplementation.

Mucosal regeneration is particularly relevant for horses with gastric mucosal lesions. Zinc supplementation can support the healing of the stomach lining after irritation.

Selenium – Small Amount, Big Impact

Selenium is an essential trace element that horses must obtain through feed. It plays a key role in protecting the cells of the gastric wall, supports the immune system, and is vital for healthy muscles. A deficiency in selenium can lead to immune weakness, muscle problems, and reduced performance.

Since selenium levels in soil—and therefore in hay—vary greatly, a deficiency can quickly occur. In selenium-poor regions, targeted supplementation is often necessary.

How Do You Recognize a Selenium Deficiency?

A selenium deficiency often develops gradually. The most common symptoms include:

• Muscle weakness and tension

• Reduced performance and fatigue

• Weakened immune system, frequent infections

• Growth disorders in foals

A blood test by your veterinarian can provide clarity about your horse’s selenium status.

Caution: Selenium Can Also Be Toxic!

Selenium differs from many other minerals in that even a slight overdose can be toxic. As little as 2 mg/kg dry matter can cause poisoning.

Signs of selenium over-supplementation:

• Hair loss and brittle hooves

• Digestive problems and nervousness

• Severe cases: organ damage or laminitis

Therefore, selenium intake should always be carefully calculated and regularly monitored!

How Can Selenium Be Supplemented?

Since selenium content in feed can vary greatly, there are several ways to supplement:

• Mineral feeds & salt licks – often contain small amounts of selenium

• Targeted selenium supplements – for precise dosing

• Organic selenium (selenium yeast) – better absorption and storage

• Inorganic selenium (sodium selenite) – lower bioavailability

Tip: Because the body absorbs selenium yeast better, it is the preferred option for safe supplementation.

How Much Selenium Does Your Horse Need?

• Pleasure horse: 0.1–0.2 mg selenium per kg of dry matter

• Sport horse / breeding mare: up to 0.5 mg selenium per kg of dry matter

• Foals: increased demand for healthy growth

If your base feed is low in selenium, targeted supplementation may be advisable. However, total intake should always be monitored and verified with a blood test.

Conclusion: Selenium – Essential, But in the Right Amount!

Selenium is vital to your horse’s health, but the correct dosage is crucial. A deficiency can impair muscle function and weaken the immune system, while an overdose can quickly become toxic. Therefore, it’s important to keep track of total selenium intake and avoid uncontrolled supplementation.

For safe and effective supplementation, selenium yeast is the better option, as it is more readily absorbed by the body than sodium selenite. To ensure optimal supply, you should regularly test your horse and supplement selenium only as needed.

Which Nutrients Generally Support a Healthy Digestive Tract?

• Magnesium and tryptophan – to reduce stress

• Pectins – for mucosal protection

• Selenium – to protect gastric cells

• Omega-3 fatty acids from linseed oil – anti-inflammatory

• Yeasts – to stabilize intestinal flora

• Digestive herbs – such as anise, caraway, and fennel

Conclusion

More on This Topic

Horses with gastric conditions need additional support. It's important to know which feeds are suitable for your horse – and which should be avoided. Visit our topic page on feeding horses with gastric issues for even more information on equine nutrition.