Published: January 2021 | Updated: September 2022
Equine stomach function and anatomy probably isn’t at the forefront of most horse owners’ thoughts. However, there are a few things performance horse owners should know about this important digestive organ, as it is the site of a common condition: Equine Gastric Ulcer Syndrome.
As the smallest component of the equine digestive tract, the stomach can hold approximately 2-4 gallons of food at any given time, and it makes up around 10% of the total volume of the digestive tract.
Compared to all other domestic animals, the horse has the smallest stomach in relation to their body size.
The equine stomach’s primary functions include mixing, storage and controlled release of feed into the small intestine, as well as secretion of the digestive enzyme, pepsin, to begin protein digestion. For the most part, nutrients are not absorbed in the stomach.
An important thing for horse owners to understand is that the equine stomach has two main sections: non-glandular and glandular. Interestingly enough, there is a clearly defined band of tissue called the margo plicatus which separates these two sections.
The margo plicatus also happens to be where gastric ulcers are often first spotted, and, in fact, the majority of gastric ulcers form somewhere along this dividing line in the stomach.
Horse Stomach Anatomy
1) Non-glandular region
The non-glandular, i.e. squamous or esophageal region of the stomach, is technically an extension of the horse’s esophagus and makes up approximately one third of the entire stomach and lower esophagus. Similar to the esophagus, this region is covered by stratified squamous epithelium.
The primary function of the non-glandular region is to serve as a reservoir for food, and as such, it is devoid of glands with secretory or absorptive capabilities. Likewise, the non-glandular region has fewer protective mechanisms against hydrochloric acid and, therefore, is a common site of gastric ulceration (again, often first forming along the margo plicatus).
2) Glandular region
The glandular section makes up the rear two thirds of the horse’s stomach and is similar to the stomach of humans and some other animals.
Here, the mucosa is dark pink and contains glands that produce gastric acid. The cells making up the glandular region include several different types of cells, each producing different secretions.
- Parietal cells produce hydrochloric acid.
- Mucous neck cells produce a thin mucus that coats and protects the glandular portion of the stomach.
- Chief cells produce pepsinogen, which converts to pepsin when hydrochloric acid is present.
The glandular region can be further subdivided into three specific sections: cardiac, fundic, and pyloric.
- The cardiac section is located closest to the margo plicatus.
- The fundic section makes up the main body of the stomach.
- The pyloric section accounts for the lowest portion of the stomach that leads to the duodenum (first part of the small intestine).
The important thing to know about the glandular region of the stomach is that its cells secrete mucus and it also contains acid-producing glands, which serve a purpose during digestion of feed but can also lead to stomach ulcers in horses when the animal is under emotional or physical stress and/or doesn’t have enough access to forage.
Your Horse’s Stomach Function Relies on Balance
Horses are “trickle feeders”, grazing for up to 18 hours a day in their natural habitat. However, many horses are stabled and, as a result, only eat at specific times throughout the day–usually two to three meals at most.
This may leave them without forage for long periods of time and, combined with high amounts of grain or concentrates, doesn’t support healthy digestive function.
When these unnatural feeding practices are combined with intense exercise, this increases the production of gastric acid which can promote the development of ulcers.
The pH of the horse stomach can range from anywhere between 1.5 to 7.0, depending on the region of the stomach that is measured.
A near neutral pH can be found in the lower portion of the non-glandular region, at the saccus caecus, but more acidic pHs can be found near the margo plicatus (3.0-6.0) and in the glandular region near the pylorus (1.5-4.0).
Equine Gastric Ulcer Syndrome (EGUS) results from an imbalance between the aggressive mechanisms (hydrochloric acid, pepsin, bile acids, organic acids) and protective mechanisms (mucus, bicarbonate) of the stomach.
Because mucosal protective mechanisms are more prevalent in the glandular region of the stomach as compared to the non-glandular region, this is where the majority of gastric ulcers form.
It’s been estimated that anywhere from 40-93% of working horses are diagnosed with EGUS at some point during their career. This would include dressage, show jumping, racing, endurance, and western performance horses.
Racehorses, however, are reported to have the highest incidence of EGUS at 66-93% of horses developing ulcers during active training periods.
Protecting Your Horse’s Sensitive Stomach
Not only is gastric ulceration painful and often performance-limiting, but ulcers can also affect your horse’s overall gut health, and possibly lead to a cascade of other health issues.
The good news, however, is that research suggests that, along with appropriate feeding and management practices, high-quality probiotics may make a difference in both preventing and treating gastric ulcers due to the fact that they support a healthy gut microbial population and help to maintain a neutral pH in the stomach.
For ongoing ulcer prevention and support, performance horses can benefit from Fullbucket’s Athletic Formula. This product is a uniquely designed power boosting formula containing eight strains of the most scientifically tested probiotics, as well as prebiotics, essential vitamins, yeast, biotin, and digestive enzymes which further improve nutrient digestibility.
Truth be known, many horses are, in fact, getting sufficient nutrients in their current diet, but due to gastric ulcers, may not be assimilating those nutrients; this is another crucial area where the Athletic Formula can help.
Aside from supporting a healthy equine digestive tract, this product also supports energy and stamina, bones and joints, hooves, skin, immune health, and fertility, so your horse will be performing at its highest potential from the inside out.