Enterolith formation is a serious problem that causes colic
in horses. Left untreated, these mineral stones will continue
to grow in the intestional tract, causing colic and intestinal
obstruction, a potentially fatal condition.
Colic and Enteroliths
There are a variety of conditions that can cause colic in
horses. Feed impactions, gas build up, intestinal displacement,
excessive sand in the intestinal tract and parasites are among
the most common causes of abdominal problems. Enteroliths,
or stone formation in the intestinal tract, are a less common
cause of colic in most horses. Because colic due to the presence
of enteroliths can be fatal, and almost always requires surgical
intervention, it is important for horse owners to be familiar
with the causes and signs of enteroliths in horses.
Enteroliths, also known as “stones” are just that- a multi-layered
deposit of magnesium, phosphorous and other minerals built
up around a foreign object in the intestines. Much like an
oyster is formed around a pearl, enteroliths can form from
the smallest piece of wood, metal, plastic that is accidentally
ingested. Over time, minerals from the hay slowly build up
around the stone, slowly increasing its size.
While some horses may pass smaller (golf ball size) stones
in their feces, most are unable to pass, and continue to grow
in the intestinal tract. Left untreated, the stones can become
larger than bowling balls, and weigh over 20 lbs. As the stones
grow in size, they can become lodged in the gradually narrowing
intestinal tract, causing an obstruction and leading to abdominal
pain of varying severity.
If left untreated, this intestinal obstruction can rapidly
lead to a rupture of the intestines, an always-fatal condition.
While enteroliths are a relatively uncommon cause of colic
in many areas, several geographic locations have an extremely
high incidence of occurrence. Horses in California are at
particularly high risk for stone formation due to the sandy
soil and alfalfa hay grown there. In fact, a study at UC Davis
found that a full quarter of colic cases treated there were
due to enteroliths, compared to a national average of less
As previously mentioned, alfalfa hay has been found to contribute
to enterolith formation. In fact, more than 99% of horses
with enteroliths had diets comprised of at least 50% alfalfa.
Alfalfa hay has significantly higher levels of magnesium,
which can contribute to the formation of enteroliths.
Several breeds of horses have been found to be more prone
to enteroliths than others. Arabian and Morgan horses in particular
have a higher incidence of Enterolith formation than many
other breeds. Special care should be taken with horses of
these breeds to develop a balanced diet to minimize risk of
The most common sign of enteroliths in horses is a recurring,
mild colic. As the stone or stones move through the intestinal
tract, they can cause discomfort and colic signs. These signs
often disappear with administration of pain medication, but
can reoccur frequently. Horses with enteroliths are often
hard keepers, have a poor work ethic, and may have occasional
Over time, the enterolith continues to grow, and in most
cases it will eventually become lodged in the intestinal tract,
causing an obstruction. Horses with an obstruction will often
show severe colic signs, and surgical intervention must be
taken immediately to remove the stones and prevent intestinal
The only non-surgical way to diagnose enteroliths in horses
is via abdominal X-ray. In many cases, a stone or stones may
be visible on the X-ray, aiding in diagnosis. However, a horse
with a seemingly normal X-ray may still have stones- they
cannot always be seen via radiographs, due to the large size
of the horses abdomen.
Exploratory Laparotomy, or colic surgery, is the only way
to treat enteroliths. Surgery will be performed to thoroughly
inspect the entire intestinal tract of the horse, and remove
any stones within it. This procedure generally has a high
success rate, unless there are complications within the intestinal
There are many ways to help prevent the formation of enteroliths
in horses. Eliminating or reducing the alfalfa content in
the diet is perhaps the most important form of prevention,
especially in high-risk horses such as Arabians and Morgans,
and horses who have a history of stone formation.
Because the formation of enteroliths has been associated
with a high intestinal pH level, feeding vinegar to your horse
may help to reduce the pH level in the gut, and inhibit stone
In addition, increasing the frequency of feedings, and regular
exercise all promote a healthy intestinal tract, and can contribute
to reducing the formation of stones.
Although relatively uncommon in many areas, enteroliths are
a potentially fatal threat to your horse. Those living in
areas known for having higher incidence of stones, and owners
of high-risk breeds should work closely with their veterinarian
to develop a care program to help minimize the risk of enteroliths.
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About the Author
Ron Petracek was raised in southern Idaho with horses and
the great outdoors. With this continued passion He now shares
through a a vast equine network. Learn more by clicking the
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