Understanding the Horse Digestive System

Understanding how the horse digestive system functions can help us prevent common gut issues—such as colic and ulcers, for example—and ensure our horses thrive.

Let’s take a closer look at how horses digest food, common digestive problems, and effective ways to support a healthy gut.

How Do Horses Digest?

“Horses are called hindgut fermenters, meaning their large intestine (including the cecum and colon) do most of the digesting, and their stomach capacity is quite small for the overall volume of the gastrointestinal tract,” explains Dr. Lynn Taylor, PhD, an equine nutritional consultant and professor of equine studies at Centenary University in Hackettstown, New Jersey.

Horses can process simple starches and sugars in the stomach and small intestine, but these types of calories are usually not a large part of their natural diet in the wild and should only be offered in small amounts.

Instead, most digestion and nutrient extraction in horses happens in the hindgut. Once food has been chewed by the teeth and swallowed down the esophagus—and starches and sugars have been extracted in the stomach and small intestine—the large intestine does most of the work.

 “The large intestine contains many microbes—good bugs like bacteria, protozoa, and fungi—to digest all kinds of fibers that make up forage,” Dr. Taylor says.

Forage—in the forms of pasture grass, hay, hay cubes, and hay pellets—is the most essential part of a horse’s diet. Giving horses consistent access to hay and/or grass is crucial to keeping their gut moving and healthy.

However, many horses in light work do not need any grain at all, only a vitamin and mineral supplement with their forage. The vitamin/mineral content of your horse’s hay may not be clear without testing each bale individually, which is very expensive.

Common Digestive Issues in Horses

Horses may experience digestive issues for a variety of reasons, and it’s important to understand how these issues develop in order to properly help your horse.

Common digestive issues in horses include:

• Colic, an umbrella term that refers to abdominal pain in horses. Colic can stem from gas buildup, a blockage, or a twisted gut, among other causes.

• Gastric ulcers are painful lesions that form in the stomach lining due to excessive stomach acid, often caused by stress, lack of forage, or excessive amounts of concentrates. Prolonged use of NSAID medications can also cause ulcers.

• Diarrhea refers to loose or watery stools caused by infections, dietary changes, or imbalances in gut bacteria. Dental issues and other age-related changes can contribute to diarrhea as well.

• Dental issues can lead to problems related to chewing and digestion due to damaged or missing teeth, which may cause difficulty eating and poor nutrient absorption. This problem is most common in older horses.

How To Care for Your Horse’s Digestive System

Beyond providing consistent access to forage, the best thing you can do to support gut and overall health is to consult a professional to formulate a balanced diet for your equine companion.

“Horses have unique nutritional requirements based on their life stage, workload, health status, metabolic status, and several other factors that influence their unique nutrient requirements,” says Dr. Rachel Mottet, PhD, an independent equine nutritionist and owner of Legacy Equine Nutrition in Ocala, Florida.

A veterinarian or equine nutritionist is best able to provide nutrition recommendations for your specific horse that will set them up for optimal health, performance, growth, and longevity.

Digestive Supplements for Horses

Digestive supplements for horses can be incorporated into the diet to help protect sensitive stomachs from ulcers, prevent diarrhea, and reduce colic risk—to name just a few.

When it comes to supplements in general, horse owners are faced with an array of options and claims that can feel overwhelming. But there are some go-to supplements that can help fix common digestive problems that are worth talking about with your veterinarian.

One such go-to supplement is gastric acid buffers, which Dr. Mottet explains “act like Tums” for people. Gastric acid buffers can help keep your horse’s stomach comfortable during stressful situations, while riding, or between meals.

“They have become increasingly popular as we’ve realized that the prevalence of equine gastric ulcer syndrome is substantial, and the associated gut discomfort can impact appetite, performance, and attitude,” says Dr. Mottet.

As a general rule, to prevent and tackle digestive dilemmas, it’s a good idea for horse owners to keep the following supplements and medications on hand:

• Oral Banamine paste is a non-steroidal anti-inflammatory (NSAID) that your veterinarian may or may not recommend administering during a suspected colic episode. Always contact your vet first before giving your horse Banamine.

• UlcerGard is the oral paste formulation of omeprazole, a preventive stomach oral ulcer medication. The prescription-strength equivalent is called GastroGard, and it requires a veterinary prescription.

• Equine GI Sponge is a clay-based powder supplement that helps firm up stool in case of diarrhea.

• Psyllium is used to help clear out sand from the gut and prevent what’s called “sand colic” if your horse is at risk of ingesting large quantities of sand. Psyllium generally comes in pelleted form.