An overview of GI issues in horses
Horses are known for having delicate gastrointestinal systems. Equine digestion is full of twists and turns, and a lot can go wrong during the process. Colic, diarrhea, ulcers, and other ailments are common in our domestic horse population. Being informed and prepared will help you react appropriately should your horse ever greet you with a bellyache.
Colic: The Main Culprit
Colic is the No. 1 killer of adult horses, accounting for 30% of U.S. horse deaths, according to the USDA’s 2015 National Animal Health Monitoring System study. While the clinical signs of colic—an umbrella term referring to abdominal discomfort—might be similar in many cases, the underlying causes and conditions can be vastly different and have a major influence on treatment and prognosis.
Michael Fugaro, VMD, Dipl. ACVS, owner of Mountain Pointe Equine Veterinary Services and a surgeon at B.W. Furlong and Associates, both in New Jersey, says the two most common types of colic he encounters on the farm are gas/spasmodic (gut spasms) and idiopathic (unknown cause), with impaction next on the list.
“Thankfully, most of these cases respond to a single treatment of medical therapy and resolve without further complication,” he says, for example, administering a non-steroidal anti-inflammatory drug (NSAID) such as flunixin meglumine (Banamine) under your vet’s guidance.
So what causes colic? “Horses are creatures of habit,” Fugaro says, “and when changes in feed, grass, water intake, medication, exercise regime, stabling, environment, etc. occur, the intestinal tract appears to be the most susceptible to that impact.”
Types of colic that end up requiring surgery vary depending on the region and horse demographic. This is because different horses in different parts of the country are exposed to different risk factors. “The signalment (age, sex, breed), occupation, and other variables of the horse appear to influence the type of surgical colic experienced,” he says. “For instance, older horses and Arabians are highly represented with strangulating obstructions secondary to lipomas (benign fatty tumors); geldings that crib-bite and/or windsuck have a higher incidence of entrapment of the small intestine in the epiploic foramen (a narrow opening connecting the two sacs of the abdominal cavity); and broodmares show a higher prevalence of large colon (the stretch of intestine located between the cecum and the transverse colon) displacement and/or volvulus (twisting) after foaling.”
Nimet Browne, DVM, MPH, Dipl. ACVIM, an internal medicine specialist at Hagyard Equine Medical Institute, in Lexington, Kentucky, with an interest in gastrointestinal disease, echoes these observations. Located in the heart of Kentucky horse country, Browne treats many Thoroughbred broodmares and foals. Common causes of medical colic in her patient population include large colon displacements, spasmodic colic, enteritis (inflammation of the small intestine), and impaction, including from parasites.
The colic type a horse experiences also depends on his age and lifestyle. “The majority of the colic cases referred to us are medical colics (those that don’t need surgery because they can be managed with intravenous fluids, pain-relieving medications, and supportive care),” Browne says. “A colic case can require surgery if pain cannot be controlled, if there is indication of gastrointestinal compromise, or if all other treatment options have failed.”
Researchers have confirmed that the faster a horse that isn’t responding to medical therapy gets referred to surgery, the greater his chance of a successful outcome. “Surgical causes of colic that we frequently see include large colon volvulus, small intestinal volvulus, mesenteric rents (tears in the membrane that anchors the intestines to the abdominal wall), intussusceptions (where the intestine telescopes onto itself), and colonic displacements,” Browne says.
While it can be difficult for veterinarians to determine the cause of a colic, she sees certain well-known predisposing factors in her practice population, she adds. These include the immediate peripartum (post-birthing) period, advanced age, stress from yearling sales prepping, horse shows, stall rest, or, as mentioned, intestinal parasite load. This article continues in the October 2020 issue of The Horse: Your Guide to Equine Health Care. Subscribe now and get an immediate download of the issue to continue reading. Current magazine subscribers can access the digital edition here.