Horses – a lot more than other animals – are prone to colic.

Colic is a very general term for abdominal pain. Specifically, an impaction colic refers to a blockage somewhere within the horse's gastro-intestinal tract causing abdominal pain and discomfort.

Seeing your horse colic can be alarming, but it is reassuring to know that most colics resolve and respond to treatment. Impaction colics fall into a category of colic presentations which can range from those that are easily treatable, through to a colic resulting from a more serious underlying condition which results in an impaction in the digestive system.

Impactions are usually caused by a build-up of solid food material, or partially formed droppings which fill a section of the gastrointestinal tract and prevent the normal passage of digested food. The large intestine is the most common region of the horse’s gastrointestinal tract to become impacted.

This is because there are several points where the large colon makes 180° turns and also reduces in diameter, creating optimum conditions for blockages to form and build up.

There are certain risk factors which are commonly associated with horses suffering from an episode of impaction colic. These include:

• A sudden change in a horses management - such as stabling a horse that normally lives out at grass (often seen in autumn to winter management of scottish horses)

• Reducing the amount of exercise that a horse gets - for example during a period of box rest after an injury

• Dehydration, or any reduction in water intake (frozen water trough/loss of supply/contaminated supply)

• Binge eating – for example a horse gaining access to the feed room or an unlimited supply of hay or haylage

• Dental disease can cause a reduction in chewing efficiency thus fibrous food is not broken down completely

• Horses that eat their straw bedding

• Horses grazing on sandy soil may take in sufficient quantities of sand to cause impaction of the colon (a ‘sand colic’ or sand impaction’)

• Reduced gut motility (as in equine grass sickness which interrupts the nerve supply to the muscles that move food along the gastro-intestinal tract)

• Repeated or prolonged sedation of a horse can slow the gastrointestinal tract

• Severe worm infestation causing a physical blockage

Clinical signs of impaction colic

Symptoms vary according to the severity and location of the impaction in the gut. In early cases of colon impaction, it may be noted that the horse is passing fewer droppings than normal and that the droppings are small, firm and dry.

The horse may become increasingly quiet; it may appear dull and depressed or refuse any feed. As the impaction builds up or worsens the horse will show signs of colic (abdominal discomfort) such as:

• Pawing the ground

• Curling of the top lip or yawning

• Laying down and/or rolling

• Look round at his flanks

• Sweating

• Rapid shallow breathing

• Kicking at his belly

• Stretching out in the stable as if trying to urinate

Immediate action

If a horse is showing signs of colic, it is important to call the vet right away as early diagnosis and treatment can improve outcome.

Its advisable to take away all food to prevent causing further impaction. If the horse is determined to roll or lay down, find a safe place such as a school where the horse can do this safely.

A thorough clinical examination including an internal (rectal) examination will be carried out by the attending vet. Several parameters, such as heart rate, respiratory rate, temperature, the amount and type of gut sounds and the feel of the internal gastro-intestinal tract, will all help to form a diagnosis of the cause of the horses colic.


If a colonic impaction is diagnosed, the vet will normally administer a combination of water and laxatives by naso-gastric tube (where a tube passed up the nose and down the oesophagus into the stomach).

Liquid paraffin is sometimes given to soften and lubricate the food material. Magnesium sulphate solution (Epsom salts) is another commonly used laxative, which acts by drawing water back into the gut thus softening the digested food material.

Painkillers, such as phenylbutazone (bute), will be given to control the discomfort until the impaction is passed. The horse must be starved and monitored to observe for any further colic signs and the amount of droppings produced.

With impaction colics, it is common for the vet to revisit in order to re-examine the horse (including carrying out rectal examinations) to check the impaction is softening and to administer more laxatives and painkillers if necessary.

Once the horse is comfortable and is passing a normal amount of droppings, small amounts of soft feed, such as grass and sloppy bran mashes, may be given, building gradually back up to normal feed and roughage in a few days.

In severe cases of colon impaction, more frequent dosing of water and laxatives by stomach tube may be required (up to every second hour), and if the food material really isn’t shifting the horse may need to be put on a drip to try and over hydrate further softening the gut contents.

This procedure would require hospitalisation and more intensive nursing and treatment. In these more severe cases, it may take a few days for the impaction to clear. It is very rare for a case of colon impaction to require surgical intervention.

Impactions of the small intestine are more likely to require surgery. These tend to be caused by the horse eating inappropriate foodstuffs or severe loss of gut motility or with a twist of the small intestine. Blockages involving the small intestine tend to be extremely painful for the horse.

The vet may suspect a small intestinal obstruction if signs of colic are severe and if he or she can feel loops of small intestine that have become distended with gas and fluid during a rectal examination.

Preventing impactions

• For stabled horses it is important to try and feed little quantities and often with plenty of good quality roughage in the diet (mimicking natural conditions as closely as possible)

• Soaking of the horses hay and adding water to hard feeds helps horses get plenty of water

• Increased water intake can be stimulated by introducing a salt lick or adding a teaspoon of salt to feed

• Horses that are prone to impaction should be out at grass as much as possible and should have regular routine dental care and assessment

• Regular exercise is a very important way to prevent impaction

• Make sure horses always have access to fresh clean water (especially in freezing conditions in the winter!).