October 14, 2016

Fall is a season of dramatic transition — from the lazy days of summer to those frigid nights in the dead of winter. It’s also the time of year when equine veterinarians begin receiving an increased volume of calls about a particularly dangerous type of induced colic known as impaction colic. Typically, the incidence of impaction colic peaks in the coldest months of winter, especially among older horses.

An impaction occurs when undigested feed moving through the gastrointestinal (GI) tract builds up, dries out and gets stuck. Impactions can occur anywhere along the GI tract, but are more prevalent in regions where the structure narrows. Two common sites of GI tract narrowing — and thus impaction — are the pelvic flexure and right dorsal colon.

Clinical signs

The first indications of impaction colic typically include lack of appetite, reduced manure production and manure that is dryer and harder than usual. As the pain becomes more severe, horses may paw the ground violently, stare at their flanks, sweat, sit on their haunches, roll or lie on their backs, sweat profusely and display muscle tremors.

Causes of impaction colic

Though not all episodes of impaction colic can be averted, preventative measures will greatly reduce the likelihood that your horse will develop this life-threatening condition. The major factors contributing to impaction colic are:

  • Decreased water intake
  • Too much concentrate
  • Inferior-quality forage
  • Poor dental care
  • Inactivity

When these factors come together in combination, the risk of impaction colic rises and the impaction can form very quickly.

Let’s take a closer look at the risk factors for impaction colic:

Decreased water intake. Adequate water intake is essential to your horse’s health. When the temperature falls, water becomes icy cold and horses will drink less because their desire for water decreases. If ice forms on the surface of the water bucket, the problem becomes exponentially worse. Insufficient water consumption can result in dehydration and reduced blood volume. The body will attempt to improve its hydration by reabsorbing water from forming feces, causing the feces to harden and promoting impaction.

Too much concentrate (grain). A common myth of horse husbandry is that grain rations and other concentrated feeds should be dramatically increased in winter to meet the animal’s higher energy requirements. Certainly, it’s a fact that horses need to eat more to stay warm as the temperature drops. But most horses are better served by offering them more forage as opposed to concentrates. Compared to grain, fibre-rich hay promotes normal and loose manure, and it also creates more heat during digestion, making it superior to grain for combatting the cold. Too much grain/concentrate in the GI tract has a way of solidifying and gumming up the works!

Inferior-quality forage. The potential for impaction colic rises in horses when they’re fed low-quality, stemmy hay. Better-quality hay costs more, but if you go to the trouble of sourcing the best forage for your horse, you’ll be rewarded immediately by a happier animal and, over the long run, lower vet fees. Also, keep in mind that eating more hay in winter encourages water intake, and you can soak hay to increase hydration even more.

Poor dental care. When food is ground into small particles through adequate mastication, it passes more easily through the horse’s digestive system. Poor dental care can undermine this essential process. If the sharp points and hooks that form on equine teeth are not removed through routine floating, chewing will become painful. Also, poor tooth balance may impede the normal chewing motion of the jaw, forcing your horse to swallow larger-than-normal pieces of hay that may move down the GI tract and promote impaction.

Inactivity. Before domestication, horses grazed continuously in winter, resulting a moderate amount of ongoing physical activity. Today, the level of activity in winter tends to be much more restricted. Unfortunately, a lack of movement slows the passage of food along the GI tract. To reduce the risk of impaction colic, try to keep your horse on a regular exercise regime throughout the winter months.

Caring for a horse in winter is challenging. While colic is not always avoidable, you’ll decrease the chance of your horse succumbing to this seasonal health issue by taking appropriate preventative measures.


Allossery Equine Veterinary Services
11499 York Durham Line
Mount Albert, Ontario
L0G 1M0

(289) 338-2068