Perhaps the number one digestive issue that comes to the minds of knowledgeable equestrians is that of colic. The most frequently seen causes of colic include high-grain / low-forage containing diets, feed containing mold or other toxins, an abrupt change in diet, dehydration, parasite infection, long-term use of non-steroidal anti-inflammatory drugs, sand ingestion, stress (from training, changes in the environment or climate, etc) dental problems and antibiotic therapy leading to the alteration of the normal microbial population within the gut. Signs of colic can be quite varied and include pawing, rolling, bloating, sweating, general distress/anxiety, loss of appetite, lack of gut sounds, excessive yawning, and curling of the upper lip (flehmen), and repeatedly looking at their sides. Some signs may be fairly subtle while others can be quite dramatic.
In addition to the causes of colic mentioned above, another category of colic is that of displacement colic. The small intestine is highly mobile within the gut as it is suspended by mesentery within the abdominal cavity. This mobility can predispose the small intestine to become twisted upon itself, leading to restricted blood flow and the demise of the affected section. This situation requires rapid resolution via surgery in order to reposition the small intestine and remove any damaged portion of it. There are a variety of other displacement conditions that can occur with the small and large intestines within the abdominal cavity. These should always be considered emergencies and necessitate surgical resolution.
In impaction colic (caused by course feed, dehydration, accumulation of foreign material such as sand, or dental disease leading to poorly chewed food) feed or other ingested material accumulates and blocks the intestine in one of the numerous sections where the large intestine changes direction (flexures) or diameter. As with displacement colics, impaction colics are most often resolved via surgery.
Gas colic occurs when excessive gas builds up leading to gut distension and abdominal pain. Gas colic can occur when a horse eats large amounts of grain, rich grass, or moldy/contaminated feed. The gas is produced by the bacteria that naturally populate the gut. Gas colic can often be alleviated by more conservative treatments such as hand-walking and antiinflammatory administration, or by insertion of a nasogastric tube by a veterinarian to remove the excess gas and fluid present in the stomach which horses are unable to vomit due to their anatomy.
Because there are so many causes of colic, and clinical signs are not always indicative of the severity of the condition, horses should be evaluated as soon as possible to determine the etiology of the colic and an appropriate treatment.