Histamines & Gastric Ulcers

Photo Cathy Dee

Why do so many horses develop gastric ulcers when they do not tick any of the boxes for the usual causes?

Many owners who contact us, whose horses have developed gastric ulcers, are out 24/7 on pasture, are not ‘performance’ horses, are not doing any extensive travel or high-intensity exercise, never go long periods without food nor do they have high grain diets.

The answer could well lie with factors that increase histamine release. We normally think of histamines in association with immune response, allergic reactions, defence against pathogens and inflammation.

It turns out that another role of histamines is stimulating stomach acid secretion.

What are Histamines?

Histamines are organic compounds primarily stored in mast cells and basophils, (which are types of white blood cells).

Laboratory studies have demonstrated that mast cells in the skin, lungs, nose, mouth, digestive tract, and blood are stimulated to release histamines when exposed to elevated potassium levels.

Hence when companies are developing ‘Anti-Histamines’ they use potassium to stimulate Histamine release in rats (☹) so they can test their products.

Excessive histamine production can lead to the overproduction of stomach acid and precipitate the development of gastric ulcers.

Another good reason for being mindful of your horse’s potassium intake.

It is the sum total of the entire diet you need to be aware of. The NRC Mineral Tolerance of Animals book states “Conservatively safe maximum tolerable levels for non-ruminants would be 10,000mg/kg” - that is 1% potassium.

Forage analyses consistently reveal short or lush green grass and legumes like clover/lucerne are at least 2% potassium as are other items like soy-bean meal, kelp, and molasses.

It is the sum total of all these items that can inadvertently become excessive and potentially affect your horse.