Function and anatomy of the horse's stomach

Horses have a unique and sensitive digestive system. The whole process 'from mouth to butt' is quite complicated. The stomach of a horse is an essential and sensitive part of this digestive process. What does that stomach actually look like and how does a healthy horse stomach function?

A horse has a very long digestive system, but the horse's stomach is relatively small. However... due to this small stomach, huge amounts of food and water must be ingested daily. An adult horse needs about 1 percent of its body weight in dry matter every day. This is a whopping 30 to 45 kilograms of fresh grass or 7.5 to 12 kilograms of hay. In addition, a horse drinks about 25 liters of water per day. If the horse has to work or if it's hot, even more water is needed!

No stretch

A horse's stomach has no stretch. The stomach of an adult horse can hold a maximum of about 25 liters, while a small pony can hold only five liters. Food remains in the stomach for about 1.5 hours, so there is a limit to the amount of food the stomach can process per hour. Too much food can lead to overload of the stomach and even to a rupture (gastric rupture). This is usually fatal. Due to the limited capacity of the horse's stomach, it is important to offer food in small portions. Especially concentrate feed, which a horse can eat quickly, fills the stomach quickly. Faster than it is emptied. Because a horse needs to chew roughage for a longer time, (a lot of) hay does not pose a risk of overloading the stomach. Hay can therefore be fed unlimitedly. You should give a maximum of one kilogram of concentrate feed (pellets or muesli) per feeding.

Anatomy of the horse's stomach

The stomach consists of two halves. The upper half is called the esophagus section, which is the part where the food enters the stomach from the esophagus. The lower half is called the bottom section, which also contains the exit to the small intestine and the rest of the digestive tract. The breakdown of carbohydrates and proteins starts in the esophagus section of the stomach. This upper half of the stomach is slightly less acidic and contains bacteria that begin to break down carbohydrates and proteins from the feed. This process results in the production of lactic acid and volatile fatty acids, among other substances. These substances are converted into absorbable protein further down in the intestines. When there is a lot of starch and sugars in the feed, as is the case with concentrate feed, more lactic acid is produced. This increases the risk of stomach ulcers in the upper part of the stomach. Feed containing a lot of fiber is important, as it prevents the upper half of the stomach from becoming too acidic. In the bottom section of the stomach, there are glands that secrete gastric juice and the enzyme pepsin. Gastric juice contains a lot of hydrochloric acid. This acid kills harmful bacteria, fungi, and yeasts that may be present in the feed. The enzyme pepsin initiates the breakdown of proteins. The stomach muscles contract and ensure that the food is well mixed with the gastric juice, forming a food mash.

Time required

In the bottom section of the stomach, there is a kind of mash. On top of that, there is a layer of liquid. The liquid food (finely chewed with water and saliva) flows directly from the stomach to the intestine. In the bottom of the stomach, the acidic gastric juice needs time to penetrate the food mash and kill harmful microorganisms. When the flow rate of the stomach becomes too high because too much feed enters at once, the gastric juice may not be able to work effectively. This can also happen if the feed is too liquid, or if the feed contains little rough cellulose. Feed ingredients with a lot of starch or, for example, a lot of wheat can clump in the stomach. If the gastric juice cannot work for long enough, harmful bacteria and yeasts can survive in the stomach and travel to the intestines. In the small intestine, these microorganisms can start producing gases, which can lead to colic.

Role of stress

A horse's stomach is very sensitive. Not only to an excess of concentrate feed, but also to a lack of roughage or too long intervals between roughage feedings. Because a horse's stomach continuously produces gastric juice, fiber-rich feed must be provided regularly. Otherwise, the stomach becomes too acidic and can also lead to the formation of stomach ulcers. The gastric juice from the bottom half of the stomach can then splash too far up. Because the stomach wall in the esophagus section is less resistant to acid than the wall in the lower part, damage and ulcers can occur. Stress is also bad for the horse's stomach. A stressed horse may produce less gastric juice than normal. This allows harmful microorganisms to survive until they reach the intestines. Once there, they can produce excessive gas and cause problems.

Supporting the stomach

To keep your horse's stomach healthy, it's important to have regular (or preferably continuous) access to high-quality dry hay. Your horse should not be without food for too long! When giving your horse concentrate feed, make sure not to exceed two kilograms per feeding and ensure that the concentrate feed has a moderate sugar and starch content. You should also provide a stress-free environment as much as possible, with social contact and enough free movement for your horse. Less stress also means fewer stomach problems. If you want to support your horse's stomach with a natural supplement, the Indian herbal mixture Triphala is a good option. This is a powder made from three types of dried fruits. This supplement supports digestion, including the acid-base balance in the stomach. Triphala also helps combat stress.

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