An Unwanted Impact
A look at how and where impaction colic happens and what measures might reduce a horse’s risk
Colic is a catchall term for almost any kind of abdominal pain, be it from gas or enteroliths, twists or blockages. The latter, which are better known as impactions, occur when consumed feed material “moves down the intestinal tract more slowly than it should, ultimately clogging the system and blocking any flow of fluid in front of it,” says North Carolina State University professor of equine surgery Anthony Blikslager, DVM, PhD, Dipl. ACVS.
Horses are particularly prone to this colic type because their intestinal tract—particularly the colon, or the portion of the large intestine that begins with the cecum and ends at the rectum—contains a number of hairpin bends around which it’s difficult for this feed material, known as ingesta, to navigate. Those bends exist because “the colon is so long that the only way to fit it into the belly is to fold it in a couple of places,” Blikslager says. The colon also requires ample fluid to digest food properly. So if a horse fails to drink enough (about six gallons a day for an adult), his risk for developing an impaction increases.
Still, the equine digestive system works very well for horses living in natural conditions—those walking and grazing for approximately 18 hours a day, Blikslager says. It doesn’t work as well when they’re more intensively managed: stabled for much of the day, with little turnout, and receiving most of their nutrients in one or two largely concentrate
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