Basic Equine Gut Health: Understanding How the System is Designed to Function Can Help Avoid Gastric Upset

By: Cynthia McFarland


Given the complexity of the horse’s digestive system, it’s not surprising that gastric disturbances are a common reason for veterinary calls.

As conscientious owners, we do our best to reduce the odds of that happening. A clear understanding of how the equine gastrointestinal system is designed to function is the best place to start.

For an animal of this size, the horse has a relatively small stomach. Horses are meant to eat numerous small meals, with long-stemmed forage comprising the bulk of their diet.

In the wild, horses spend as much as 16 to 18 hours a day foraging. Along with eating around the clock, they are on the go, moving about to locate forage and water.

Compare this active and continuous eating lifestyle to that of most domesticated horses today. Depending on where they live, some horses may spend a significant amount of time on pasture grazing. But the reality for many horses is a stall with an attached run, if they’re lucky, or turnout in a small paddock or dirt lot.

Further complicating the picture is the common routine of feeding large meals a couple times a day. This practice leaves the stomach empty much of the time and vulnerable to ulceration by acidic gastric fluids.

“We do know that horses are designed to eat small amounts very frequently during the day, so a departure from this towards large meals fed in bulk twice daily can have some adverse effects on the gastrointestinal system as a whole,” says Kate Christie, DVM, DACVIM (LAIM), a specialist in Large Animal Internal Medicine with Rood & Riddle Equine Hospital in Lexington, Kentucky.

Normal digestion

Whether we’re talking about the mustang, the high-level performance horse, reliable school master, breeding stock or backyard trail horse, all equines have the same digestive system.

Horses are adaptive animals, but this doesn’t change the fact that they are non-ruminant herbivores. This means the majority of the digestive process takes place in the hindgut through fermentation.

Horses are very different from ruminants like deer, cattle, sheep, and goats who digest food by fermentation in their foregut, which consists of a rumen and multi-chambered stomach.

The horse’s small stomach only holds about 2 to 4 gallons at a time. Food is meant to pass quickly through the stomach and on into the small intestine, which is a remarkable 50 to 70 feet long.

Digestion starts here, but food moves rather rapidly through the small intestine. Under normal conditions, food is moved along at about 1 foot per minute on its way to the hindgut where the balance of digestion occurs.

The small intestine handles the digestion and absorption of protein, fat (oil), and some starch.

Fermentation begins once the food material reaches the hindgut, which consists of the cecum, large colon, small colon, and rectum.

Under normal conditions, feed material reaches the cecum a little less than an hour after the horse is fed.

Once entering the cecum, it’s normal for the feed material to take two to three days to completely pass through the rest of the digestive tract.

Upsetting the system

When we take away the horse’s optimal environment of freedom to move at will and forage all day, we throw a wrench into the way his digestive system is designed to work. It’s then up to us to do everything we can to enhance digestion.

Depending on what and how the horse is fed, there is potential for upsetting the digestive system.

For example, a common trigger for gastric upset is feeding a meal that is heavy on grain, but light in forage.

Starch that wasn’t digested in the small intestine can undergo rapid fermentation in the cecum, which drops the pH, alters the microbiome, and may lead to gastric upset.

Hindgut acidosis can occur with an abrupt drop in pH, as the increased acidity has the potential to cause diarrhea and ulceration.

“As far as problems of the equine stomach go, Equine Gastric Ulcer Syndrome (EGUS) is far and above the most common pathology that we deal with as equine veterinarians,” notes Christie. (We’ll take a deeper dive into EGUS in an upcoming article.)

The same management and feeding practices that contribute to EGUS can also make horses susceptible to colic. Being mindful of this and making strategic changes to your feed routine can greatly reduce the risk of gastric upset.

Proactive steps

Consider both what, when and how you feed.

Forage (hay and/or pasture) should be the foundation of every horse’s diet, no matter their breed, discipline, or age.

“Access to forage continues to be an important point when talking about the proper function of the horse’s GI tract,” says Christie.

It should be noted that this doesn’t necessarily mean large volumes of exceptionally high-quality hay. Small amounts of forage fed frequently is key.

“Every horse should have readily accessible forage for as much of a 24-hour period as possible,” notes Christie. “This is really the best way to ensure proper function of the GI tract.”

“Slow” feeders, small-hole hay nets or timed feeders can be beneficial in keeping hay in front of horses for longer periods of time.

Pasture turnout can be protective in more ways than one. Not only does it afford access to forage, but it also provides companionship from other horses and decreases stress.

Grain/concentrate and supplements should be added to the diet when the horse requires more energy, protein, fat, or additional nutrients than forage alone can supply. For example, performance horses in heavy work typically need more calories and nutrients than what is provided by hay only.

“There are so many excellent commercial feeds out there that have been designed with the equine athlete in mind,” says Christie.

She recommends avoiding grains that are high in excess starch when designing a nutrition plan for your horse.

“Avoiding textured feeds and sticking with a pelleted complete feed may provide you with less of an acidic rollercoaster when it comes to the pH of the stomach contents,” says Christie. “These feeds are more than capable of providing the extra calories your competition horse needs. Ensuring that energy comes from easily digestible sources and that calories from fat are the focus can also help limit the amount of starch and carbohydrates that the horse receives.”

Also, keep in mind how much grain/concentrate you feed at one time. Ideally, you’ll want to give no more than 4 to 5 pounds per meal. For example, if your horse eats 9 pounds of concentrate per day, break that amount down into two, or even three, small meals evenly spaced throughout the day and fed with forage.

You may have heard that feeding hay before grain helps reduce the risk of gastric upset.

“When it comes to feeding hay before grain, the important thing isn’t necessarily the timing of meals, but that the horse has constant access to some type of forage,” says Christie.

“Ideally, the horse should always have some amount of forage in the stomach. In some cases, this may mean feeding hay prior to grain. Having hay present in the stomach at the time of a grain meal can help slow processing of the grain within the stomach to allow for proper digestion and handling of the components of the grain,” she explains.

Don’t overlook the importance of water to the digestive process. Horses should always have convenient access to clean, fresh water.

Added protection

Some horse owners find that adding Vita Flex Pro Daily Gastric Care to their feed routine supports gastric health and a normal pH, which can help manage digestive stress.

The supplement is formulated with ingredients specifically chosen for their beneficial effects on promoting a healthy gastric environment.

Based on research results, here’s a closer look at these ingredients and what they do.

Pectin acts with lecithin to form a hydrophobic barrier on gastric mucosal membranes. Together, these ingredients help protect gastric mucosal membranes from the corrosive effects of gastric acids.

B-glucan forms a gel that acts to coat the stomach lining.

Calcium Carbonate helps to neutralize gastric pH for 2 to 4 hours post consumption.

Sodium Bicarbonate is a buffering agent that helps to neutralize gastric pH.

Magnesium Oxide supports proper muscle function and a healthy nervous system and has been shown to have a calming effect in nervous horses.

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