Gastrointestinal Impaction in Horses

Gastrointestinal impactions are common in horses. Horses’ digestive tracts are adapted to process numerous small meals throughout the day, reflective of their grazing lifestyle. With current management strategies, horses frequently receive 2-3 large meals, encouraging overeating of a large amount of fiber at one time. In some cases, the digestive tract is unable to process such a large amount of feed, resulting in impaction.

Horses that are showing signs of abdominal pain and are not defecating as much as usual, even when these signs are subtle, require emergency veterinary attention.

The severity of impaction depends on where in the gastrointestinal tract the impaction is found, how long it has been there, and whether it has fully or partially blocked the passage of digested food. In many cases, as the severity increases, the signs of colic worsen.

Contributing factors to impaction include

• Fibrous feed that is difficult to digest
• Reduced water intake
• Lack of exercise
• Disruption to intestinal function
• Poor dental health
• Dehydration
• Ingestion of non-food matter such as sand, pieces of rope, hair, rubber, etc.
• Use of certain medications

All horses are at risk of impaction, although miniature horses have increased risk.

Horses with increasing signs of abdominal pain require emergency veterinary attention. Subtle signs of discomfort also require veterinary care because the most dangerous form of impaction, that found in the cecum, is not often associated with severe signs of distress. Horses suspected of having an impaction should not be fed until it is resolved.

In general, impaction is caused by a mass that blocks the movement of food and water through the digestive system. This can be because food matter becomes too bulky and dry to pass through the bends and narrowings of the digestive tract, or because the tract is not functioning well enough to move digesting food along properly.

Impaction at certain locations along the GI tract are associated with specific causation factors.

When impaction happens in the esophagus it is called esophageal impaction and is associated with:

• Eating too quickly (bolting feed)
• Insufficient chewing

When impaction happens in the stomach, it is called gastric impaction and is associated with certain feeds including:

• Beet pulp
• Straw
• Barley
• Pelleted feeds

Impaction of the small intestine is associated with:

• Ascarid worm infestation

When impaction happens in the final segment of the small intestine it is called ileal impaction and is associated with:

• Disruption to the contractions of the ileal musculature, the cause of which is unknown
• Infestation of the intestinal tapeworm Anoplocephala perfoliata
• Feeding of Coastal Bermuda Hay

When impaction happens in the pouch that marks the border between the small and large intestine (the cecum) it is called cecal impaction and is associated with:

• Recent surgery
• Abnormal muscular activity
• Sand ingestion

Impaction that happens in the large colon is associated with:

• The hairpin bends of the structure itself
• Foreign body obstruction
• Sand ingestion
• Meconium retention (in newborn foals)

Impaction that happens in the small colon is associated with:

• Fluid retention
• Miniature horses (which are particularly susceptible)

Diagnostic tools include:

• Physical examination
• Rectal palpation
• Nasogastric intubation (a tube put into the nose to release built up fluids or gasses)
• Bloodwork
• Ultrasound

Nasogastric intubation should always be performed by a veterinarian. There is no safe way to intubate a horse at home.

Horses often have to be sedated for diagnostic examination.

Treatment plans depend on the location of the impaction. Non-surgical interventions include:

• IV fluids
• Enteral fluids (a tube through the nose delivers fluid directly into the stomach for horses who are unwilling to drink)
• Carbonated fluids to break up the impaction
• Laxatives
• Intestinal lubricants
• Enemas
• Pain medication

In severe cases, surgery may be required.

Treatments that successfully clear the blockage generally return the horse to good health within 24-48 hours. Impactions that require surgery have a more guarded prognosis. Prognosis also depends on the location of the impaction, with cecal, ileal, and small colon impactions having the poorest prognosis. In severe cases, cecal impaction can lead to rupture of the cecum, necessitating euthanasia. Esophageal, gastric, and large colon impactions have an excellent prognosis.

Prevention of impaction is aimed at recreating the natural eating pattern of the horse. These include:

• Offering small meals 5 or more times a day
• Offering unlimited access to clean water at all times
• Encouraging water intake, including warming water during winter and adding flavoring to water for horses that are not interested in plain water
• Cleaning and refilling buckets and troughs regularly
• Maintaining exercise routines and physical activity at all times of the year
• Wetting feed and forage to soften it and to add fluids to the diet
• Changing feed to softer, more digestible alternatives

Impaction of the stomach is rare. Other forms of impaction are common, especially in horses that are fed fewer, larger meals, those who do not drink sufficient water, and those that do not exercise daily.

• Oral fluids
• IV fluids
• Enteral fluids
• Carbonated fluids
• Laxatives
• Intestinal lubricants
• Enemas
• Pain medication
• Surgery