Impaction Season

Colic remains the #1 health issue of horses across all ages, sexes, breeds and uses. There are many forms of colic and impaction is one of the most common.


The stringy, sticky, white/tan coating on this manure is mucus, a red flag warning sign for impaction.

Several things have been identified as risk factors for colic, including reduced exercise, diet change and tapeworm infestations.  These factors converge in the fall and winter with a diet change from pasture being a double whammy because of the very low moisture content of hay compared to grass.  Tapeworms are picked up during grazing season so have reached peak numbers and size.  It doesn’t help matters that bot fly larvae attached to the stomach lining have also reached a large size and may cover a significant amount of the stomach’s surface.

Early signs are easy to miss. Manure is present initially but total volume is less.  Some manure may have a coating of mucus.  The horse also continues to eat but will gradually decrease amounts. There is depression but obvious signs of colic do not usually appear until the obstruction is complete or near complete.  The horse often continues to pass manure for a while even when blocked because any manure that was present past the impaction will continue to move out.

Pain severity varies but can be quite dramatic in some horses. However, the color of their mucus membranes/gums remains good.  Pulse is moderately elevated.  They usually respond well to analgesics such as flunixin meglumine (Banamine) but typically need twice daily dosing.  When pain reduces because of treatment they will often eat, but eating quickly causes more pain.

Treatment also involves fluids intravenously and/or by stomach tube.  Softeners, mineral oil and/or osmotic laxatives like magnesium sulfate are commonly used.  Most cases resolve without surgery in about 3 days, but it can take as long as a week for the blockage to clear.  Enemas are sometimes used as the blockage moves closer to the small colon and exiting.

The most important part of avoiding impaction is keeping the horse and his intestinal contents well hydrated.  The best way to do this is to guarantee adequate daily salt intake.  For an average size horse that is not exercising/sweating this is at least 1 oz (2 tablespoons) per day. Horses over 1100 lbs need more.  Add this directly to the bucket meals. If the horse won’t eat enough salt this way, dissolve it in water and spray on the hay.

There must also be a constant supply of water at a palatable temperature – often a tall order in cold weather.  They will drink the most during and after eating and if the water is around body temperature. If you don’t  have hot water in the barn, invest in a heating coil. Make watering the last chore and offer warmed water two or three times a day.

Make sure the horse spends as much time as possible moving around outside the stall.  In addition to reduced manure output and drier fecal matter, Williams et al 2015 found significantly reduced large intestinal motility when horses were moved from pasture to stall confinement with light exercise.

Finally, don’t neglect a combined praziquantel and ivermectin or moxidectin deworming this time of year.

Impaction colic is rarely life-threatening but causes considerable pain and often runs a prolonged course.  You can reduce your horse’s risk by management that focuses on hydration, as much exercise as possible and removing parasites.

Eleanor Kellon, VMD



About Dr. Kellon

Graduate of University of Pennsylvania Veterinary School. Owner of Equine Nutritional Solutions,, industry and private nutritional consultations, online nutritional courses. Staff Veterinary Expert at Uckele Health and Nutrition .
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