4 common scenarios that increase your horse’s colic risk

Colic. It’s a dreaded word in the equine community. This broad term used to describe abdominal pain is the No. 1 killer of horses of all ages. It’s also the top reason for an emergency vet call, note researchers on one study (Bowden et al., 2017). With the rapid decline it can cause and potentially fatal consequences, colic is not something veterinarians take lightly.

In this article we’ve partnered with two colic researchers to help you identify and navigate four situations that increase your horse’s colic risk. Sarah Freeman, BVetMed, PhD, is a professor of veterinary surgery at the University of Nottingham’s School of Veterinary Medicine and Science, in England. Her areas of interest include equine surgery and colic. Louise Southwood, BVSc, Dipl. ACVS, ACVECC, PhD, serves as a professor of large animal emergency and critical care at the University of Pennsylvania School of Veterinary Medicine, in Kennett Square. Her expertise lies in equine colic, the gut microbiome, and critical care. Let’s dive in.

Scenario 1: Management Changes

For a long time we had little scientific insight behind the reasons horses colic. It wasn’t until 2019 that Freeman and her team published the first-ever systematic review quantifying risk factors for colic in adult horses—a massive undertaking that involved reviewing 52 publications and identifying the Top 22 risk factors for colic (see table below).

To many seasoned horse owners it might not come as a surprise that the risk factor Freeman’s team identified most frequently was change in management. Whether that involves their feed, caretaker, or stabling arrangement, horses’ digestive tracts seem to respond poorly to change.

“We need to keep everything as consistent as possible and in a natural environment,” says Freeman. “Five or six days of relatively intense exercise followed by one or two days of complete rest in a stall is a significant variation in routine. We can reduce that change by providing free turnout on the days the horses are not exercised and offering similar amounts of pasture access on days when in exercise compared to days of rest.”

In a different study Freeman and her team looked at the physical and social impact of moving pastured horses into a stable. She says they found changes in living conditions came with:

• Reduced gut motility.
• Fewer and drier feces.
• Reduced water intake.
• Reduced movement.
• Lack of social interaction.

“These findings revealed how big of an impact common management changes can have on equine health, especially digestive health,” she notes.

Regarding the lesser-known and unexpected colic risk factors identified in her study, Freeman takes the data with a grain of salt. In some of the studies evaluated, for instance, researchers found correlations between feeding a whole-grain diet and an increased risk of colic, while others found the opposite: a decreased colic risk.

“Risk factors associated with management changes are often difficult to interpret, as there are multiple factors involved,” explains Freeman. For example, she isn’t convinced that exercising a horse more than once a week is truly a significant risk factor for colic. “We only have data from one study, so the evidence is relatively weak. We need more studies showing similar findings before making assumptions.”

What does prevail across the board is the value of keeping things consistent and natural. Of course, some changes are unavoidable. Life happens, horses get sold, move to new barns, and must adapt. When change is necessary, the key is to use transition periods to introduce new elements gradually, mixing them with the old whenever possible. This is particularly important when introducing a new feed.

Scenario 2: Dehydration

Horse owners are well-known for worrying about their horses’ drinking habits when temperatures drop and water troughs freeze—a justified concern, given proper water intake is necessary to ease the passage of grass, hay, and feed through the gut. If your horse does not have access to a fresh water source or does not drink enough water voluntarily, he could end up with an intestinal blockage and impaction colic.

Colic cases very often arrive at the hospital dehydrated, requiring intravenous (IV) fluids. It begs the question: Does the dehydration cause the colic, or does the colic cause the dehydration? Is it a vicious cycle?

“It depends,” says Freeman. “Horses with colic caused by intestinal strangulations and those related to diarrhea develop dehydration as a result of fluid loss through the gastrointestinal tract. Intestinal twists, for example, can rapidly develop severe fluid imbalances due to damaged or dying intestine.”

Other times, the narrative is reversed. “Impactions may have dehydration as an underlying cause, but the impaction will suppress drinking and cause further fluid imbalance, both of which worsen the dehydration,” Freeman continues. “Food blockages also disturb the normal fluid secretion and reabsorption in the intestines. These cases, therefore, do turn into a vicious cycle of colic and dehydration.”

Scenario 3: Gut Microbiome ­Disturbance

The horse’s intestines—just like ours—are populated with trillions of beneficial bacteria, viruses, and fungi, collectively known as the gut microbiome. Changes in diet and stress (from travel, competition, etc.) seem to throw the gut microbiome out of whack. This again points to the larger change-in-management risk factor that increases colic risk. When the delicate balance of the gut microbiome is disturbed, all sorts of health issues—­including colic—can ensue.

“It takes time for the horse’s gut physiology and microbiota to adapt to new forage and the microbiomes it contains,” says Freeman. “Our research suggests that the gut physiology needs at least two weeks to adapt to a change in diet. This all goes back to management, and the focus should be on a gradual feed ­transition.”

Southwood adds that the exact pathophysiological link between gut microbiome disturbances and colic is something she and other scientists are still trying to understand. New studies on the topic are constantly emerging.

Scenario 4: Postpartum

Eleven percent of all mares that deliver a foal experience colic shortly after (Salem et al., 2019). Scientists have long suspected postpartum colic episodes are tied to gut microbiome changes that occur naturally during and shortly after the birthing process. But they have not confirmed this theory. In recent studies, including one in which researchers examined fecal samples of broodmares from the last three weeks of pregnancy until seven weeks postpartum, they concluded that fecal microbiota remains relatively stable and functional throughout the periparturient (around the time of foaling) period. Any variations were deemed to be associated with individual mare flora. What causes mares to colic after foaling, then?

There are likely several reasons. Large colon volvulus (twisting) is a common presentation, accounting for 36% of all postpartum colic cases (Salem et al., 2019). Broodmares are 13 times more likely than other horses to develop the condition (Suthers et al., 2012). Vets believe the high prevalence is associated with the many management changes that usually accompany the postpartum period—notably, diet changes as the mare switches from gestating to lactating overnight, with caretakers meeting her all-time-high energy demands largely with concentrates. Changes in diet and large amounts of concentrates are known risk factors for gut microbiome disturbance and colic. Therefore, our sources say an indirect correlation between the postpartum period and colic in broodmares likely exists, with the direct link being changes in management and diet.

Reducing Colic Risk Through Management

Given our management practices’ potential to increase or reduce colic risk, Southwood has come up with a list of top husbandry recommendations to keep a horse’s gut happy and healthy:

• Increase pasture time, and reduce time spent in a stall.
• Avoid access to sand and gravel, which the horse can inadvertently consume, causing accumulation the gut and leading to large colon impaction colic or problems with recurrent colic.
• Feed good-quality hay.
• Minimize feeding concentrates when possible. Forage should make up the bulk of the diet. If your horse doesn’t need the extra calories from ­concentrates, you should instead feed a fortified ration balancer to meet his vitamin and mineral needs.
• Provide ad libitum access to clean water that does not freeze in winter.
• Design a parasite management plan in consultation with your veterinarian to include strategic anthelmintic administration. Heavy internal parasite burdens can cause many health problems, including colic.
• Provide regular dental care by a qualified equine dentist. Inadequate chewing can allow large food boluses to make their way into the intestines, resulting in a blockage.

Final Thoughts

Sometimes when a horse suffers from colic, it’s due to factors entirely beyond our control. In many other cases we can prevent colic episodes by adopting management practices known to promote digestive health. Review your horse’s living conditions, diet, and routine, and ask yourself, “Am I doing everything in my power to keep his gut healthy?” If you see room for improvement, have a conversation with your barn manager and veterinarian. You could save yourself heartache and financial strain down the road.