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Why an acid horse stomach makes horses sick!

Tanja Dietz


4 Min. Lesezeit

Audio version – listen to this article easily

You are what you eat - this saying also applies to our four-legged partners. Feeding according to needs and requirements is the basis for a healthy horse that is ready to perform. In this article we would like to explain to you in more detail what is important in horse feeding, what path the feed takes in the horse and what the pH value is all about.

Secure a free feed sample of Equine 74 Gastric and help your horse to buffer  excess stomach acid, so it feels well again.

The basis for a good digestion begins in the mouth. Chewing does not only break down the feed. It also stimulates the flow of saliva via the parotid gland. Saliva is essential for the further course of the entire digestion. It has a pH value of 8 and is therefore alkaline. It contains bicarbonates that buffer the acid in the horse's stomach.

The horse's stomach has different sensitivities

The stomach is divided into two sections. The front section of the stomach, where the food enters after the oesophagus, is glandless and has a sensitive mucosa. In this section of the stomach low microbial conversions take place. 

Mainly easily digestible carbohydrates such as sugar and starch, but also proteins are broken down. The waste products are lactic acid and small amounts of butyric and acetic acid, which acidify the gastric juice. The breakdown of nutrients produces furthermore ammonia and digestive gases.

The peristaltic movements of the stomach ensure that the stomach contracts. The contractions mix the food mush with gastric juice and saliva and move the mixed mush forward. Glands are embedded in the mucous membrane of the rear section of the stomach. The gastric juice is formed in the so-called fundus area. It contains pepsin, the enzyme which is needed to break down proteins. Furthermore the fundus area contains hydrochloric acid.

During the passage through the stomach, the pH value of the mush is reduced from about 5 - 6 to under 3. To prevent the stomach from digesting itself in the rear part the stomach is lined with a thick layer of mucus containing glands.

How quickly the feed slurry leaves the stomach depends on the particle size and the ratio of carbohydrates that are soluble in the stomach to those that are insoluble. The higher the proportion of insoluble carbohydrates, the faster the mash passes through the stomach. The larger the insoluble carbohydrates, the slower the passage of the food.

It is therefore important for horses to chew their feed thoroughly and to salivate sufficiently, so that the gastric acid can come through the mash evenly. This is also important to kill germs that were ingested with the feed. 

Enzymatic digestion in the small intestine

The digestion that has begun in the stomach is continued in the small intestine. In simple terms, starch is broken down into glucose and simple sugars, protein into amino acids, and fats into fatty acids, which in turn are absorbed from the intestine into the blood due to their small particle size.

Microbial digestion takes place in the large intestine. Those components of the feed that cannot be broken down enzymatically in the small intestine enter the large intestine. In the best case, this is mainly raw fibre.

In the large intestine, or more precisely in the caecum, microbial digestion of the raw fibre takes place. Responsible for this is the intestinal flora. Countless microorganisms (intestinal bacteria) break down the raw fibre and use it for themselves as a source of nutrients. In the process, they produce B vitamins and energy in the form of fatty acids, which are available to the horse.

They are absorbed from the large intestine into the blood. Unlike humans, whose appendix has no significance because it can only synthesise 5-10 % of their energy needs with the help of the intestinal microbes, the horse's intestinal microbes can provide up to 80 % of the needed energy. 

Gut microbes are sensitive

The intestinal microbes are dependent on fibre-rich feed. They depend on what the horse eats and what later reaches the back of the large intestine.
Since each horse is individual and eats differently, the intestinal flora of each horse is just as individual as the horse itself. Among other things, the amount and type of soluble and insoluble fibres play a role here.

Furthermore, the buffering capacity of the intestine or the amount and type of nutrients flowing in from the small intestine play an important role too. Too much starch leads to a shift in the balance of the intestinal flora and thus to disturbed digestion. Likewise, a too low pH value and thus a too acidic feed mush damages the sensitive constellation of bacteria.

Therefore, it is essential not only for the stomach but also for the intestinal health that the feed mush is not too acidic.

Conclusion: Too much concentrated feed not only damages the stomach, but also the intestine.


If the amount of concentrated feed is too high, too much undigested starch passes through the small intestine and enters the large intestine. This causes an increase of  carbohydrate-splitting bacteria. These bacteria produce lactic acid as a decomposition product. In addition, large amounts of volatile fatty acids are released. Together with the lactic acid the volatile fatty acids lower the pH value, which causes the death of essential fibre-digesting bacteria.

The resulting toxins pass through the intestinal mucosa into the blood and thus into the horse's entire organism, where they have a vascular damaging effect. In the worst case, laminitis can be the result.

More informations about gastric ulcers

Check out more articles about gastric ulcers in our blog and read about the 20 most important symptoms horses show when suffering from gastric ulcers right here

Interested in more reliable and easy-to-read information about your horse's  well-being? Explore our free eBooks.

Equine 74 Gastric

The long-term solution

Buffers the excess acid in the horse's stomach instead of blocking it.

Equine 74 Stomach Calm Relax

In case of acute stress

Supports the nervous horse stomach in stressful situations.