Digestion starts at the tip of the nose
There is hardly a more complex topic in horse feeding than the digestive system itself. Most horse owners probably do not know that lips and teeth, which are responsible for food intake, are already part of the digestive tract. The duration and intensity of chewing depends, among other things, on the structural content of the feed. This is why concentrated feed is eaten much faster than roughage such as hay. While chewing, the horse produces saliva, which is mixed with the feed pulp. A horse can even produce up to 5 kg of saliva per 100 kg of body weight per day! [1]
Horses cannot vomit
The chewed and salivated food passes through the esophagus into the horse's stomach. Unlike humans, horses cannot vomit. This is due to a strong muscle at the entrance to the stomach that prevents the food from flowing back into the esophagus. Because of this, however, an overloaded stomach is extremely dangerous for horses. With a capacity of around 15-20 liters, the horse's stomach is very small in relation to its body size. [2] This is one of the reasons why frequent, smaller meals are advisable for horses. A maximum amount of concentrate feed of 0.3 kg per 100 kg of body weight per meal is recommended. [3]
Horses have a single-chamber, compound stomach. This means that the stomach consists of two parts, the glandular part and the glandless part. In a gastroscopy, this separation can even be clearly seen visually, as the two parts are actually visibly separated by a border line (margo plicatus). [4] The two parts are also colored differently. While the upper part of the stomach, which has no glands, is white, the lower part, which contains glands, is reddish.
What is stomach ulcers?
Stomach ulcers are often found exactly at the transition between the two parts. This is because the glandless part of the stomach is not designed to come into contact with stomach acid. As a constant eater, the horse produces stomach acid continuously, regardless of whether it is eating or not. Long breaks in feeding (> 4 hours) can lead to excess acid. Stomach acid can therefore attack the sensitive glandless mucous membrane in the upper part of the stomach. As you can imagine, this is a very painful matter for horses. Stress of any kind, too much concentrated feed or pain can also lead to stomach ulcers. Symptoms of gastritis or stomach ulcers are extremely varied and are therefore sometimes not recognized. As a preventative measure, we recommend providing horses with sufficient roughage, i.e. at least 1.5 kg of hay per 100 kg of body weight. The breaks in feeding should also not last longer than 4 hours if possible. In many cases, stomach protection can be fed to horses with sensitive stomachs. Mucus-forming ingredients also line the stomach and protect the mucous membrane from aggressive stomach acid. Nevertheless, in the case of stomach ulcers, the cause should be investigated and the trigger eliminated if possible.
Horses do not have a gallbladder
The pre-digested food passes from the stomach into the intestine. Depending on the size of the horse, the intestine of the horse can be up to 40 m long. The small intestine takes up a large part of this at around 25 m. The digestion of starch, fat and proteins, for example, takes place in the small intestine. A special feature that distinguishes horses is that they do not have a gallbladder. In this case, bile acids are continuously produced by the liver and neutralize, among other things, stomach acid. The bile acids also support the digestion of fat.
Without an appendix, nothing works for a horse!
The horse's large intestine consists of the cecum, the large and small colon and the rectum. Compared to other species, the horse's cecum is very large at around one meter long and its function is essential! Without the cecum, a horse could not survive, quite unlike humans. The cecum and the colon are the two fermentation chambers of the digestive tract. The horse's large intestine is primarily responsible for digesting crude fiber. But B-complex vitamins, vitamin C and vitamin K are also produced and absorbed by the colon bacteria. Therefore, the body is not fundamentally dependent on their intake. However, digestive problems or a disturbed colon flora can lead to the balance of the intestinal bacteria becoming out of whack and possible deficiency symptoms. Causes of such an imbalance in the colon flora can also be antibiotics or certain medications, for example. Stress or spoiled feed can also trigger dysbiosis in the colon.
If there is a suspicion of an imbalance in the colon flora, it may be useful to supplement B vitamins, for example. Feeding live yeast Saccharomyces cerevisiae can also support the microorganisms in the colon and restore balance.
Dysbiosis can also affect stool consistency
The large intestine is also where water and liquid are reabsorbed (re-absorbed). An imbalance in the intestine can, among other things, affect the absorption of water in the intestine, which can lead to diarrhea and watery stools. There are a variety of different causes for watery stools and diarrhea. In general, however, we recommend keeping an eye on the intestinal flora when diarrhea and watery stools occur. To support this, you can feed supplements with water-binding properties that improve the consistency of the stool. Products containing pectin, kaolin or psyllium seed husks are suitable for this. Pectin also has positive effects on the stomach lining.
[1] Meyer, H. & Coenen, M. (2014) Horse Feeding (5th Edition) Enke Verlag, Stuttgart
[2] Meyer, H. & Coenen, M. (2014) Horse Feeding (5th Edition) Enke Verlag, Stuttgart
[3] FN (2017) Basic knowledge of keeping, feeding, health and breeding, guidelines for riding and driving Volume 4, FNverlag der Deutschen Reiterlichen Vereinigung GmbH
[4] Nickel, R. & Schummer A. & Seiferle E. (1999) Textbook of the anatomy of domestic animals. Volume 2, 8th edition, Parey Verlag, Berlin & May, A. & Venner, M. & Cavicchioli, E. & Gehlen, H. (2012) Gastric diseases of horses - diagnostics and therapy, equine medicine 28 (2012) 4 (July/August) 388-405
