horse colic

Every two years, the Equine Science Society (ESS) holds a symposium covering the latest equine nutrition and physiology research. Anthony Blikslager, DVM, PhD, Dipl. ACVS, professor of equine surgery and gastroenterology at North Carolina State University, in Raleigh, kicked off the 2019 edition, taking place June 3-6 in Asheville, North Carolina, with his perspective as a surgeon on horse colic prevention.

Here are eight interesting facts from his lecture:

1. Equine veterinarians can’t tell what type of colic (e.g., ileal impaction, large colon volvulus, etc.) a horse is experiencing based on clinical signs alone. What they can determine is when medical treatment isn’t working and when signs are getting more severe—both of which suggest a horse might need to go to surgery.

2. Colic treatment has been made more complicated by barn managers and caretakers having access to pain-relieving non-steroidal anti-inflammatory drugs (NSAIDs), such as phenylbutazone (Bute) and flunixin meglumine (Banamine), on the farm, Blikslager said. These drugs can give them the impression that clinical signs have resolved when, in fact, they haven’t. Ideally, owners should be notifying their veterinarians when administering an NSAID, said Blikslager. And as a rule of thumb, he said, horses should respond to the first round of NSAID treatment. If they need a second round, the veterinarian should discuss with the owner referral to a hospital.

3. The major themes in colic prevention revolve around feeding (forage type and quality) and management (meal frequency, parasite control, housing/stalling, etc.). “Managing these can help prevent colic in the future,” said Blikslager.

4. Colic prevalence is sometimes associated with horses consuming coastal Bermuda hay, which is commonly grown in the Southeastern United States. In fact, a 2002 study found horses fed coastal Bermuda hay were six times more likely to develop ileal impaction than horses fed other grass hays.

Blikslager presented one theory as to why, emphasizing it hasn’t yet been proven: “Coastal hay is much finer, stemmier hay. If horses aren’t used to it, they don’t chew it properly and unintentionally swallow longer fibers than they should. This can clog the ileocecal junction like hair in a drain.”

5. Horses pass approximately 150 liters, or 40 gallons, of fluid through their gastrointestinal tract each day. Meal feeding, in particular, causes massive fluid fluxes through the digestive tract, essentially dehydrating and rehydrating the large intestine repeatedly, which can put horses at risk of colon impaction.

6. On average, food travels 20 meters (about 65 feet) through the horse’s stomach and small intestine and into the cecum and large colon fairly rapidly—within two to three hours. This means concentrate feeds enter the colon relatively undigested, said Blikslager, triggering microbiome changes and the large fluid fluxes mentioned above.

7. Psyllium is a popular daily supplement for preventing sand colic in horses that graze on sandy soils. In theory it reduces sand levels in the gut, but Blikslager said it might act more like a prebiotic, which gets digested by the microbiome within the colon. This could, in turn, result in increased short chain fatty acids, which might have positive effects on the microbiome and gut motility, thereby speeding sand passage.

8. Broodmares are at risk of large intestinal strangulating obstructions post-foaling. Blikslager hypothesized reasons for this: the big physiological changes that take place right after foaling (i.e., more space in the abdomen); significant changes in exercise levels as mares are stalled to foal, then turned back out; nutritional changes during lactation; and microbiome changes. He said this latter cause is a promising future research focus.

Take-Home Message

In sum, Blikslager said owners and veterinarians must learn to better recognize horse colic risk factors (e.g., foaling, hay type, etc.) and focus on management changes such as feed quality to prevent the condition from developing. Researchers should continue to study the significance of the microbiome and refine optimal management practices revolving around feeding and turnout.