Published January, 2010

Among the species of domestic livestock, the horse is the animal that most commonly suffers from colic. Colic is a general term indicating abdominal pain. The anatomy of the horse's digestive tract, how the tract works, and the management practices imposed by man seem to contribute to colic's occurrence. Colic might not be caused solely by diseases of the intestinal tract. In fact, infections elsewhere in the body, as in the urogenital or respiratory tracts, as well as pregnancy might cause the horse to present with clinical signs of colic. A survey in 1986 by the Morris Animal Foundation reported that colic was the leading cause of death in horses and the No. 1 health concern of horse owners.

The amount of money spent on the disease is impossible to totally assess, because not only are there treatment costs, time is also lost are involved. In 1983 the equine insurance industry paid $16 million for claims directly attributable to colic. Therefore, horse owners need to know the causes, clinical signs, diagnostic and treatment procedures and preventive measures to reduce colic's incidence.

Causes

There are main types of colic, and there are a number of possible causes. Factors such as sudden changes in the weather and feeding (frequency, quantity or quality of feed), and overexertion or chilling may lead to colic. Spasmodic colic is charaterized by severe contractions of the intestines. Intestinal obstruction or a twisted intestine creates a very severe condition resulting in extreme pain. The veterinarian should diagnose the possibility of an obstruction or twisted intestine as early as possible, because such a condition is potentially life-threatening and requires surgery.

Historically, veterinarians have considered the most common cause of colic to be internal parasites:

• Migrating strongyle larvae damage blood vessels in the intestines, decreasing blood supply, which leads to necrosis (tissue death), decreased motility, and pain.
• Large numbers of roundworms can cause impaction or obstruction of the intestines.
• Administering dewormer (anthlemintics), particularly to horses overloaded with internal parasites, can cause colic.

Clinical signs do not always result from a disease of the digestive tract. They also can arise from infections elsewhere in the body, from infectious diseases like rabies, pleurisy (inflammation of the thin, transparent membrane covering the lungs and lining the chest cavity), and dermatitis, and habits:

• Conditions affecting the locomotor system, like laminitis and other forms of lameness, can lead to signs of colic. Certain conditions might lead to an intestinal obstruction, which will cause colic symptoms.
• Horses with certain oral vices (bolting, cribbing) are also prone to colic.

Diet can cause colic symptoms:

• Horses kept in sandy paddocks or overgrazed pastures are predisposed to suffer from "sand" colic. In this situation, ingested sand obstructs the intestine.
• Spoiled silage and enteritis can also obstruct the large intestine.
• An obstruction may also occur if the horse ingests a foreign object.
• Sudden changes in feed, (either type or quantity), or moldy feed can cause colic due to improper fermentation in the gut or an obstruction.
• A diet predominantly made up of concentrate can lead to colic if an adequate supply of long-stem roughage is not provided.
• Lack of water can also lead to clinical signs of colic and might even cause an impaction. Remember to avoid allowing a "hot" horse after heavy exercise to drink heavily or eat, as doing so can not only lead to colic, but to other serious sequelae of colic, such as laminitis.

Clinical Signs

A horse with mild colic will paw the ground with his front feet, appear restless, lie down and roll frequently, and look at his abdomen. A horse with more severe colic will roll more vigorously and may become cast and lie on his back to relieve intestinal pressure. A horse with very severe colic will throw himself to the ground and roll violently. Such a horse can be dangerous to work with until he is properly sedated. Pulse and respiratory rates rise, while temperature typically remains within a normal range. The absence of abdominal sounds is characteristic of a horse with colic.

Diagnosis

Your veterinarian should conduct a thorough examination to determine the colic's severity and plan treatment as soon as possible after the clinical signs start. Until your veterinarian arrives, walk the horse to help relieve anxiety and prevent rolling, which can lead to injury. Walking might also help the horse restore normal intestinal activity and allow him to defecate and/or relieve the buildup of pressure in the intestines. If 30 minutes pass and the clinical signs either are unrelenting or increasing in severity, it's imperative that you have a veterinarian's assistance.

First observe the horse in its stall or paddock.

Note the following:

• General condition and behavior (calm, restless, alert, dull, apathetic)
• Frequency of abdominal pain (none, intermittent, or continuous)
• Frequency of abdominal sounds (normal, increased, decreased, or absent)
• Abdominal size (normal, reduced, distended)
• Nature of peripheral pulse (that palpable in the extremities, e.g., legs, neck, head; normal or weak)
• Packed cell volume
• Capillary refill time (the length of time it takes for gums to return to normal color after pressure is applied, an indicator of the quality of blood circulation through this area)
• Other signs (sweating, wounds, etc.)
• Water intake
• Presence of and consistency and regularity of feces

Further examination of the colic patient includes a measure of pulse and respiratory rates (normal resting pulse rate is 36 beats/minute and respiration rate is 8-16 breaths/minute), rectal palpation, and passing a stomach tube. Based on what he or she finds during an ultrasound of the abdomen, the veterinarian might choose to pass a stomach tube to release fluids or gas from the stomach (ingesta only goes one way in the horse and releasing this pressure can not only serve as a treatment for the horse's discomfort, it can help the veterinarian assess the colic's severity, along with a rectal exam, the diagnostic ultrasound mentioned, and sometimes even an abdominal tap.).

After these observations, the veterinarian can suggest a treatment, depending on the type of colic. For example, veterinarians can treat a mild, intermittent colic conservatively, while a horse with a twisted intestine (torsion) requires surgery.

Treatment

After an initial exam to determine the type and severity of the colic, a veterinarian might involve using analgesics (pain relievers). Often he or she gives the horse mineral oil (about 1 gallon) through the nasogastric tube to lubricate the tract and to act as a laxative to help fecal matter move through the tract.

Evaluate the horse in the period following the initial treatment. Because of the possibility that the intestines might have an obstruction, check the horse at frequent intervals (hourly or more frequently, in some cases) following the initial treatment. If it doesn't appear that the horse's clinical signs have been alleviated, the veterinarian should consider that the horse has an intestinal obstruction, and surgery might be necessary. Have your truck and trailer (or a transportation arrangement) ready for such a scenario. In this case, you will want to call ahead to the referral hospital so the veterinarians are expecting your horse. When making the decision to go to a referral hospital, it is important to understand that the costs of hospitalization and surgery may be significant. Being prepared to deal with the financial aspects ahead of time is important. Also, in situations where the animal has insurance (major medical or mortality), it will be important to contact the insurance adjuster and bring appropriate contact information with you to the hospital.

Prevention

Avoiding colic involves many parameters. Most important is proper management. Avoiding situations which predispose the horse to colic will undoubtedly reduce the incidence of colic.

Here are some practical steps to reduce chances of colic:

1. Do not overgraze pastures and paddocks (horse will be less likely to ingest sand).

2. Provide a clean, and abundant fresh water at all times.

3. Feed on a regular schedule from day to day.

4. Do not feed moldy or spoiled grain or hay.

5. Provide adequate long-stem roughage in the horse's diet.

6. Keep stalls and paddock areas free from foreign objects that the horse might ingest.

7. Put all horses on a regular, properly designed deworming program. This step is imperative.

In general, good, practical horse management, along with common sense, can help the horse owner avoid situations which could predispose horses to colic. If signs of colic do arise, contact your veterinarian.

This fact sheet was prepared by the equine section, Department of Animal Sciences via Cooperative Extension Service, University of Kentucky, College of Agriculture.