Every horse will, from time to time, swallow small nonfood objects. Pebbles, clumps of hair, pieces of twine, wire, and other foriegn bodies can usually pass through the horse’s digestive system without issue. In some cases, though, thin layers of minerals build up around the object, forming a enterolith.
Enteroliths in horses, colloquially known as “gut stones,” or “equine pearls,” may be eliminated through the manure while they are still small. In some horses an enterolith will continue to snowball until it causes a blockage or rupture. It’s common for horses that suffer from recurrent colic and other gastrointestinal symptoms to have one or more enteroliths.

Symptoms Of Enteroliths In Horses
One fo the telltale signs of enteroliths in horses is the presence of small stones in the manure. However, these passable stones are easily missed, and some horses will have just one large stone, rather than many small ones.
Recurring colic, diarrhea, unexplained weight loss, and changes in mood can occur. You might notice grumpiness that comes and goes, or your horse may refuse to exercise.
A horse can have an enterolith for years before it starts to cause outwardly visible physical symptoms. They generally start in the large intestine and become an issue as they move into the narrower small intestine, where they can cause a blockage. Left untreated, a gut stone can cause an intestinal rupture, which is usually fatal.

Why Do Horses Get Enteroliths?
Enteroliths can occur in horses of any age, sex, or breed, though they rarely occur in horses under 4 years of age. They’re significantly more common in certain regions, including California, Arizona, Ohio, Texas, and Florida, possibly because of the mineral content in the soil, feed, or drinking water. They affect Arabian and Morgan horse breeds more often than others, indicating that some horses may have a genetic predisposition for developing enteroliths.

Prevent Enteroliths In Horses
Diet appears to contribute to the formation of enteroliths. In clinical studies, the colon contents of horses with stones typically have higher concentrations of magnesium, calcium, and phosphorus, and a high pH. Horses that eat alfalfa, especially if it makes up more than 50% of their diet, are at greater risk for developing gut stones.
Horses that have had enteroliths are usually recommended to be given a diet that’s low in alfalfa hay. A high-fiber diet like oat or grass hay can help foreign bodies move through the gut more quickly, before stones can form. It’s helpful for horses to get plenty of exercise to promote gut motility and daily grazing at pasture.

How Are Enteroliths Treated?
Enteroliths are usually diagnosed with x-rays, though they do not always show up. If there are smaller enteroliths present in the manure, flat sides indicate that there are others inside the horse’s colon.
Surgery can confirm the presence of stones that may not be visible on an x-ray. It’s also the only way to treat enteroliths that cause colic. Once the stone is removed, it can be broken to reveal the foreign body at the center. Enterolith surgery has a high success rate and most horses go on to have a full recovery.