Common Causes Of Impaction Colic In Horses: Health Knowledge Equestrians Must Know 2021


A common type of colic, impactions result in a partial or full blockage of the intestines. Usually caused by a solid mass of food, impactions can be worsened by dehydration. Learn to listen to you your horse’s gut sounds. A lack of normal, gurgling stomach and intestinal sounds can indicate a blockage.

Impaction colic is also called obstructive colic. A common cause of impaction or obstructive colic is irregular or inappropriate feeding schedule.

If your horse goes too long between meals, he may eat too quickly. His small stomach and complex digestive tract are not built for gorging and this can lead to to trouble.

Horses fed on the sandy ground can develop sand colic and impactions. Grit, gravel, and sand can irritate the intestinal wall and slowly build up, impairing intestinal motility and creating a blockage.

Other common causes of impaction colics in horses include:

Enterolith Impactions

Enteroliths, hard crystals made primarily of magnesium, ammonium and phosphorus, form in the colon and can cause colic. Small stones are passed in the manure, but some remain and grow larger over time. When they get big enough, they can cause an obstruction characterized by chronic or persistent colic.

Enterolith colics are more common in the western US, where alfalfa hay is used as a major source of roughage. They are sometimes called protein colics.

Alfalfa contains high levels of magnesium and has a high protein content. As the protein digests in the colon, ammonium is released and binds with the magnesium and phosphorus, the building blocks of enteroliths. At the same time, alfalfa hay creates an alkaline environment in the colon favorable to the formation of enteroliths.

Some water sources, too, can contain high levels of magnesium. Have your water tested to determine if you have “hard” water, and consider adding a water softener to reduce mineral levels.

Reduce your horse’s alfalfa consumption. At least half of your horse’s daily roughage should be grass or grass hay. Be aware that wheat bran contains high levels of phosphorus, too. A cup of apple cider vinegar twice daily can help to acidify the colon.

Equine Dehydration

We usually associate dehydration with hot, humid weather, but it can occur at any time. In fact, winter dehydration is common in horses because they don’t like to drink very cold water. To prevent or reverse mild dehydration, get your horse to drink more water.

Sign of equine dehydration include:

  • Dry mucous membranes of the inner eyelid and gums
  • Sunken eyes
  • Fatigue and weak pulse
  • Elevated heart and respiratory rates

Tests that you can perform include the CRT (capillary refill time), skin tenting and jugular vein refill speed. You should be familiar with your horse’s healthy, baseline readings in order to interpret the results of these tests.

  • CRT Test: Press your horse’s gum lightly. The skin will blanch as blood is pushed away from the site. Color should return to normal within 2 seconds.
  • Skin Tenting Test: Pinch the skin on the front of your horse’s shoulders, near the neck. The skin should spring back quickly.
  • Jugular Vein Refill Speed Test: Press the large vein that runs the length of your horse’s neck (the jugular). It will reform quickly in a hydrated horse.

Fiber and Horse Colic

Wheat and oat straw may cause impaction colic in horses. These materials contain highly non-digestible fiber that do not ferment in the hindgut. Unlike cattle, horses can’t digest these forages. 

Bermudagrass hay has been implicated in ileal impactions, but good quality bermudagrass cut and baled by a reputable source, is safe. 

Bermuda hay has a low moisture content and fine fibers that may form obstructive masses so access to clean, fresh drinking water is crucial. Horses do not chew this hay as thoroughly as other, more coarse-fibered grass hay and may overeat if fed free choice. For pasture grass, seed with Alicia, Coastal, Tifton 85, and Jiggs varieties.

Consider adding a live yeast supplement like PROBIMAX EquiColic Colic Prevention Aid to prevent the pH drop in the hindgut that can lead to colic. 

Plants That Cause Impaction Colic

Feeding your horse poor quality, hard-to-digest hay has been implicated in equine impaction colics but other plants can cause blockages, too. 

  • Mesquite

Mesquite (Prosopis glandulosa beans are very high in sugar and starch and may cause obstructions of the small and large intestine.

  • Persimmons

Ripe persimmons (Diospyros virginaia) may contribute to impaction colics. The plant fibers form a hardened mass in the digestive tract of your horse that may disrupt or block the small or large intestine. Pain and discomfort may not appear until several months after consumption. 

  • Hawthorne

Cockspur hawthorn (Crataegus crusgalli) fruits may cause equine impaction colic or diarrhea.

Yeast Culture and Horse Colic

Live yeast culture helps break down fiber in your horse’s complex digestive tract. Combined with other beneficial microbes, these compounds reduce colic and intestinal gases, aid digestion, improve organic phosphorus absorption and increase dry matter digestion. 

PROBIMAX® is a concentrated source of live yeast cells and digestive enzymes. It’s available in a powdered form that can be added to feed or in a convenient, squirt-in-the-mouth paste.

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