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Constipation is an abnormal condition that is recognized by the body's inability to expel food that has been digested. In horses, the term “impacted” is used to describe constipation. The inability to defecate may be due to an underlying medical condition that requires treatment, but may also be related to stress or poor diet. Large amounts of digesta become impacted most commonly in the large colon of the horse. This leads to abdominal pain and becomes a medical condition called impaction colic.

If prolonged, constipation can lead to severe health problems. The suppressed movement of waste from the body can be toxic to the system, and when added to increasing abdominal pain, the horse becomes dehydrated and systemically ill. The physical weight of the impaction can also damage the lining of the colon.

Horses usually have a bowel movement shortly after eating and normally defecate multiple times per day. If you notice that your horse is not having regular multiple bowel movements in one day, this may be indicative of a greater problem and you should notify your veterinarian.

Symptoms and Types

• Lack of manure production
• Decrease or lack of appetite
• Colic – severe pain in the abdomen
• Laying down, lethargy, depression

Causes

• Obstruction due to impacted food material or foreign material such as sand or even intestinal stones (enteroliths) or ingested hair (trichobezoars)
• Presence of parasites in the digestive system, which can act as a blockage in the intestinal tract
• Dehydration
• Decrease in exercise (winter and summer months)
• Inability to chew as thoroughly due to dental issues (typically found in older horses)

Diagnosis

You will need to give a thorough history of your horse's health, onset of symptoms, and possible incidents that might have led to this condition. Your veterinarian will then perform a thorough physical exam on your horse, taking into account the background history of symptoms that you have provided. Your vet will usually perform a rectal exam on your horse, which allows him/her to palpate some portions of the intestinal tract. Oftentimes, an impaction in the large colon can be palpated rectally.

Unlike with small animals, X-ray imaging is rarely used to view the intestinal system of a horse because of the horse’s large size.