Impaction colic in horses

Good management can help prevent impaction colic.

Photo by Karen Waite

Photo by Karen Waite

What is colic in horses?

Colic may be defined as serious abdominal pain, which in horses may be caused by a variety of things. Colic is a serious problem in horses and ponies, and in some cases it may be fatal. In fact, colic is unfortunately considered to be the number one killer of horses, although colic can range from mild to serious, depending on its cause.

Common types of colic

Three common types of colic include gas colic, spasmodic colic, and impaction colic. While this lesson will focus on impaction colic, we will start with a definition of gas and spasmodic colic.

Gas colic is caused by excessive production of gas in any portion of the horse’s intestinal tract. It is believed that sudden changes in feed may contribute to gas colic, so it is important to make sure that horses have constant access to good quality hay and clean water, and changes in feed should be gradual. If treated promptly, the prognosis of gas colic is usually very good.

Spasmodic colic is defined as painful contractions of the smooth muscle in the intestines. This type of colic typically responds well to treatment by a veterinarian, and may be caused by overexcitement or stress. Spasmodic colic is similar to indigestion in humans.

Impaction colic is caused by obstructions in the bowel, typically in areas where the large intestine changes in direction or diameter. These obstructions may be caused by dry, firm masses of feed, or foreign material such as dirt or sand. Impaction colic can be very serious, or even fatal, and often (usually) requires treatment by a veterinarian.

Signs of colic

A horse that is experiencing abdominal pain or colic may stretch it’s body, paw, roll frequently, look at its flank or belly, may start to sweat, or seem depressed. Typically a horse that is experiencing colic will demonstrate some, but not necessarily all of these signs. Occasionally, horses will lie down, and stay quiet, but not roll. If this is the case, it is not necessary to force the horse to walk, as tradition often dictates, although movement may help move the impaction along the tract. If the horse does start rolling violently, however, the horse should be walked until veterinary help arrives.

What contributes to impaction colic? 

Horses are non-ruminant herbivore, which means they eat fibrous feeds like grass and hay, but do not have a large rumen like cattle and sheep, to extensively digest the fiber. As a result, the horse has a complex digestive tract, which includes a relatively small stomach, a very long small and large intestine, and a cecum that contains fiber-digesting microbes. Given the length of the tract, it makes many turns to fit into the abdominal cavity of the horse, and also changes in diameter periodically. These turns and diameter changes provide locations where dried feed and foreign substances may get caught, blocking the flow of digesta through the tract and causing an impaction. If the impaction is not released (relieved), gas may be produced, which distends the tract, ultimately producing pain, or colic. In severe cases, the tract may become trapped, twisted, and/or displaced) cutting off blood flow (and ingesta movement), which can be very serious and require surgery. In addition, the tract may rupture, ultimately requiring the euthanasia of the horse.

It is critical that mature horses at maintenance consume at least 10-15 gallons of clean, fresh water daily and more in hot weather, or when the horse is working. Water will both aid in the prevention of dehydration in the horse and keep feed moist, thus decreasing the risk of impaction colic. Making sure there is salt available or top dressing loose salt on grain will also typically keep horses drinking.

Making sure that horses have good quality feed in a sufficient quantity will assist in the prevention of impaction colic as well. Mature horses will consume 1.0-2.0% of their body weight in feed daily, the majority of which should come in the form of hay or pasture. Hay or pasture should not contain many weeds, or overly mature plants with tough woody stems, as these also can cause impaction colic.

When horses overgraze pasture or are allowed to graze on sandy soil, they often consume dirt and sand which can block the cecum and colon, which can also cause impaction colic. Not allowing horses to graze pastures to a grass height of less than 3-5”, or on sandy soil, can aid in the prevention of impaction colic.

While horses may develop colic symptoms for a variety of reasons, Michigan State University Extension suggests that good management may help prevent some impaction colic.

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