The risk of colic in winter is well known, but don’t let your guard down during the summer. Two types of colic can strike as a result of warm weather conditions, and knowing how they occur will help you to prevent them:

• Impaction colic. Dehydration from heavy sweating and/or reduced water intake, combined with dry hay or pasture in a drought situation, can lead to impaction colic. These impactions commonly occur at the pelvic flexure, the location where the large intestine doubles back on itself. A horse with simple impaction colic may seem only mildly uncomfortable, but if the blockage compromises blood supply to the intestine, pain can quickly intensify.

Veterinarians typically diagnose impaction colic with a rectal exam and by noting the absence of reflux (fluid backed up in the stomach) through a nasogastric tube. (If there is reflux, the problem is more serious, and the blockage is probably in the small intestine.) Treatment involves nasogastric fluids, laxatives and possibly intravenous fluids to rehydrate the horse and soften the mass, along with medication to control pain until it passes. In the rare cases when a blockage doesn’t clear on its own, the horse may require surgery.

Prevent summer impaction colic by ensuring your horse has plenty of fresh water at all times. If you’ve provided water but suspect your horse is drinking less than he usually does (most horses drink between five and 10 gallons a day) or if he shows any signs of dehydration, such as dark gums or skin that stays “tented” when pinched, call your veterinarian for advice.

• Gas colic. When grass recovers after a drought-breaking rain, the sugars it contains can ferment in an unprepared digestive tract, leading to gas colic. This is essentially Mother Nature causing the very same sudden dietary shift horse owners are cautioned to not make themselves. Gas colic can be intensely painful as the bubbles work their way through the digestive tract.

Your veterinarian will diagnose this type of colic based on rectal palpation, the absence of reflux when a nasogastric tube is passed and the horse’s response to analgesic medications; gas colics typically respond very quickly to a dose of flunixin meglumine or buscopan. Most gas colics resolve with time, but movement of a large gas bubble can cause an intestine to twist, cutting off the flow of blood. In these cases, medication does not relieve pain and surgery is needed to repair the twist and restore circulation.

To prevent gas colic in the summer, be cautious about how much you let your horse graze during times of pasture growth and regrowth. A grazing muzzle will allow him to enjoy turnout while limiting his grass intake.

This article first appeared in EQUUS #379

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