Decreasing the Risk of Colic in Horses

Many factors may cause the pain associated with colic in horses. The most common are:

• Spasms caused by contractions of the bowel wall.
• Distention from a buildup of gas, fluid, or ingesta that causes expansion of the bowel.
• Traction, a result of pulling on the bowel.
• Ischemia (decreased blood flow) of the gastrointestinal tract because of dehydration, blockage of a blood vessel by a clot, or compression of a blood vessel.
• Inflammation caused by stress, parasites, nonsteroidal anti-inflammatory drugs, sand, infectious colitis, or ingested toxins.

One study showed the incidence of colic is greatest among horses 2 to 10 years old. Further examination of this group revealed colic was related more to the stressful occupations (racing, three-day eventing, etc.) of the horses rather than age.

Management appears to play the greatest role in decreasing the risk of colic. Pasture turnout with a fresh water source appears to carry the lowest colic risk because horses are able to continually ingest small amounts of food throughout the day. Inclusion of concentrates in the diet tends to increase the likelihood of colic, and the risk escalates as the amount of concentrates fed increases. Feeding horses up to 5.5 pounds (2.5 kilograms) of concentrates slightly increased the risk of colic compared to feeding only roughage. Feeding 5.5 to 11 pounds (2.5 to 5 kilograms) of concentrate was five times more likely to cause colic than feeding only roughage. Horses eating more than 11 pounds of concentrate were six times more likely to colic.

The horse’s gastrointestinal system is designed to process roughage diets. Fresh grass in early spring is considered a readily digestible carbohydrate. Therefore, there may be an increased risk of spasmodic colic in horses grazing pasture if they have not previously been kept on pasture.

High-quality hay is important in decreasing the risk of colic. Abruptly changing from high-quality hay to poorer quality hay may predispose the horse to impaction due to decreased digestibility.

Alfalfa (lucerne) has been associated with the formation of enteroliths (mineral masses that form in the colon of a horse). These stones can become so large they may block narrow portions of the large intestine, such as the pelvic flexure or the transverse colon. Enteroliths are found in horses in any part of the country but seem to be more predominant in the western United States, presumably because alfalfa is the primary source of roughage.

Read more from Advances in Equine Nutrition III.