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Anatomy of colic

Colic is a general, catch-all term used to refer to any sort of abdominal pain in horses (in layman’s terms, it’s a belly ache). Based on that definition, the term “colic” could be used to describe gastric ulcers or problems in the small intestine. However, for the purposes of this article, when we say colic, we’re referring to problems in the primary organs that make up the hindgut: the cecum and colon. Together, these organs are responsible for digesting the complex carbohydrates your horse eats, including all of his forage (hay, pasture, and other roughage). Since at least 60% of your horse’s diet should be made up of forage, there’s a lot of work to be done!

How it works

After food makes its way through your horse’s foregut (stomach and small intestine), it arrives at the first part of the hindgut: the cecum. In the cecum, forage is digested by friendly bacteria that ferment and break down fiber into volatile fatty acids, which are usable sources of energy for your horse. Additionally, these bacteria are responsible for producing some B-vitamins and other vital nutrients. The fermentation process continues in the large colon and the small colon, which are also responsible for reabsorbing most of the water present in the digestive tract.


What goes wrong

Graze Anatomy
In his natural habitat, your horse would graze for approximately 17 hours daily to meet his nutritional needs. As a result, his digestive tract is designed to rely on a slow, steady intake of complex carbohydrates like grass and hay.
However, constant access to fresh pasture can be hard to come by and many horses don’t (or can’t) have access to free choice hay. Unfortunately, that can contribute to an unhealthy hindgut and problems such as excess gas, impaction, loose stool, and other causes of colic.
Serving Up Trouble?
Typical fortified grain is full of simple carbohydrates (sugars and starches), which are very different from the structural carbohydrates found in forage. This can be problematic for your horse’s hindgut, especially if he’s being fed large meals. Large grain meals are difficult for the stomach and small intestine to digest sugars and starches fast enough, allowing them to pass undigested into the hindgut. Because the hindgut wasn’t meant to digest simple carbohydrates, doing so can alter the delicate pH balance and lead to problems such as colic and diarrhea.

Inside look at colic

There are a number of different types of problems in the hindgut that can
cause your horse to colic, ranging from excess gas to physical displacement
of an organ. Here, we’ll take an inside look at four unique colic examples:

Nephrosplenic ligament entrapment (A.K.A. Left Dorsal Displacement)
This occurs when the large colon is displaced and gets trapped between the left kidney, the spleen, and the nephrosplenic ligament.

After a horse has colic surgery, adhesions (or scar tissue) may develop in the intestines and cause blockages in the digestive system.

This scientific term refers to a twist in which the small intestine rotates or flips, cutting off circulation and food passage.

Pedunculated lipoma (Fatty Tumor on Long Stalk)
When the stalk of a benign fatty tumor in the abdomen wraps around and strangles the intestine, the blood supply is cut off, damaging that section of intestine.

Colic risk factors

Research has shown there may be things you’re accidentally doing (or not doing) that are proven to increase your horse’s risk of colic.


Risk factor: Lack of turnout

Your horse was built to roam and graze. Increased stall time can increase your horse’s chances of digestive upset.

Smart tip
Maximize turnout time to keep your horse moving (and, ideally, grazing) to support normal gut motility. If you can’t turn your horse out, try handwalking and hand-grazing to mimic that natural meandering behavior.


Risk factor: Large amounts of grain

Studies have shown that horses fed large amounts of grain (more than 5 lbs./day) are at a greater risk of developing colic.

Smart tip
Make sure your horse is receiving 1–2% of his body weight in forage every day. If he still needs grain, feed the minimum amount possible in multiple, small servings throughout the day.


Risk factor: Grain changes

Grain changes, including changes in amount, type, or brand, can cause a fivefold increase in colic risk.

Smart tip
Change grain gradually, ideally blending the old and new grain for 7–10 days. You may also want to look for a digestive health supplement to help support the microbes of the hindgut during transitions.


Risk factor: Hay changes

Changes in hay, including switching types or feeding a new cut, can increase your horse’s chances of developing colic by ten times!

Smart tip
Change hay as gradually as possible, ideally blending the old and new hay for 7–10 days, to ease hindgut stress, and consider adding a digestive supplement for daily support.


Risk factor: Sudden changes in exercise of activity

Sudden changes in exercise or activity level have been shown to increase digestive disruption, increasing colic risk. The most problematic change is a sudden decrease in work and turnout, which is often associated with a horse going on stall rest due to injury.

Smart tip
Keep your horse’s exercise and turnout schedules as consistent as possible, and make any adjustments as gradually as possible.


Risk factor: Failure of proper deworming

Failure to receive appropriate deworming doubles your horse’s risk of developing colic.

Smart tip
Work with your veterinarian to create an individualized deworming program tailored to your horse’s needs. Optimal parasite control includes fecal egg counts, strategic use of dewormers, and conscientious herd and manure management.


Risk factor: Hay quality

When hay quality decreases, so does digestibility, leading to an increased risk of colic.

Smart tip
Feed the highest-quality hay you can find, ideally choosing a leafy, bright green hay with a fresh aroma and no signs of mold, mildew, or dust.

Warning signs of colic

Tell-tale signs of potential GI upset

  • Looking at, kicking, or biting abdomen
  • Repeatedly lying down and getting up
  • Not eating or drinking
  • Sitting in a dog-like position or lying on the back
  • Lip curling (Flehmen response)
  • Lack of bowel movements
  • Reduced or absent gut sounds
  • Stretching out as if to urinate
  • Elevated respiratory rate
  • Elevated heart rate
  • Pawing
  • Sweating
Posted in Health & Nutrition

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6 comments on “Anatomy of colic
  1. Nicole S. says:

    Great article! Thank you so much for clarifying such a traumatic event so thoroughly and in such simple terms. Would love to read more 🙂

  2. stefanie says:

    my horse went thru colic 2 weeks ago. thanks to my instructors keen eye, she caught it early and he has made a full recovery. the warning signs listed in this article are very accurate. this is great information for all horse owners. thank you!

  3. Jennifer says:

    Thank you for this article, it shows what my vet was telling me happened to my horse. He had an impaction in his large colon, and the picture of a horse’s system helped me see exactly what she was explaining.

  4. Nancy says:

    Wonderful blog! My horse is recovering from colic (large intestine impaction as well) thanks to swift recognition from the barn staff of the symptoms. Your signs are spot on! Every stable owner should post them. Although I attempted every avoidance task in a move from MN to OR, there are some things that just add up and no matter what you do, you’ve got a higher risk (feed changes and exercise, weather change and turn out). I’d love to see a follow-up blog on post-colic care. It is just as critical to manage care over the 7-10 days post as it was to catch and halt the colic episode.

  5. Danita Craven says:

    Very imformative and simple for a complete understanding of a serious life threating ailment that concerns my horse

  6. Ethical Equestrian says:

    Sad to read this after the extremely painful Colic death of a Fourth Level Oldenburger mare, about fifteen years old. It was at Keenridge, Hilda Gurney’s farm, Summer 2015. Maybe no one noticed or didn’t know the symptoms. If Colic can kill here, it can happen anywhere. Make sure eveyone knows symptoms of Colic and the Vet arrives in time.

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