The digestive system of a horse

The oral cavity
k3

The entire process begins in the oral cavity of the horse. The tufts of grass that the horse tears off with its front teeth when grazing or the concentrate or forage feed that it gathers with its muzzle (nose) get crushed by its cheek teeth and mixed with saliva. The horse’s teeth have an essential function in this context and hence, it is import to regularly check the dental health of your horse.

Chewing mixes the feed in the horse’s mouth with saliva. The horse produces large amounts of saliva every day (around 10-15 litres) and unlike the saliva of other mammals, there are no enzymes in the saliva of a horse. It is, however, rich in bicarbonate. In addition, saliva is important for the regulation of acids in the digestive system of the horse. Consequently, it is important for the horse to be able to eat in peace and quiet and for a relatively long period of time – so that its feed can get properly salivated. This will also give the feed a consistency that facilitates its movement through the rest of the horse’s digestive system.

Forage feeds make the horse produce more saliva than concentrate feeds. Hence, it is recommended to give the horse a little bit of forage feed before it is given its concentrate feed. This also extends the horse’s feeding time – essential for the process of salivation. This is because the stomach of a horse has no so-called stretch receptors. Instead, it is the overall feeding time that creates a feeling of satiety or fullness. A gentle and relaxed feeding pace will also reduce the risk of blockages in the food pipe (oesophagus).

The food pipe (oesophagus)
k8

The food pipe is the link between the horse’s mouth and stomach. The food pipe in a horse is superficially located and it is quite easy to see a ‘lump’ of swallowed food move down the left side of the pipe.

The food pipe of a horse is sensitive. The the feed is not properly wet through with saliva or if the horse has consumed something that it finds difficult to digest, there is a risk of the horse suffering from choke. This is when the food pipe gets blocked with parts of food. Horses that tend to rush their feeding ought to be fed on the floor/ground in order to reduce the risk of choke.

The stomach
k22

The stomach of a horse is small in comparison to the rest of its body. As a result, the food it eats does not stay long in its stomach. The upper opening (upper orifice) of the stomach is fitted with a strong valve that prevents the emission of stomach contents or gases. Horses cannot burp or vomit. As a result, the horse’s stomach may become very bloated when there is a build-up of gases. This usually occurs when large amounts of starch react with the bacterial flora of the stomach and begin to ferment and produce gas which then does not pass fast enough through the digestive system of the horse. The problem is often caused by the horse having consumed large amounts of cereal during a short period of time.

Upon entering the stomach, the feed comes into contact with the acidic gastric juice. This, in turn, activates the enzymes required for the extraction of nutrients in the small intestine of the horse.

The feed continues into the small intestine via the lower end of the stomach also known as the pylorus. Bile is now added in the bile duct, making the fat in the feed soluble in water and also, a source of energy. In the pancreas, bicarbonate is secreted which helps bind the acidity of the feed. The same secretion also provides the enzymes needed to break down proteins, fats and carbohydrates.

The small intestine
k21

In the small intestine, digestible energy substances used for explosive muscle activity are extracted and then stored in the muscle and fatty tissues of the horse. The horse has a fairly limited capacity to absorb this type of carbohydrates, the nutritional importance of which should not be exaggerated. The small intestine boasts an impressive length of around 20 metres and the contents of the horse’s stomach pass through it with an incredible speed. It takes no more than 1 hour for the feed that the horse swallows to finish its journey through the small intestine. Next stop is the main collection point in the horse’s stomach – the large intestine.

The large intestine
k11

Most of the nutrient extraction in the horse’s stomach takes place in the large intestine and the cecum where the feed is processed further by bacteria, fungi and unicellular organisms. The chemical processing of the feed is now finished. And the microbiological processing takes over.

The large intestine can be likened to a large ‘sausage’ which takes up nearly 2/3 of the total volume in the abdominal cavity. Here, the content of the stomach remains for up to 3 days while it is being processed by a large number of microorganisms. One single gram of the large intestine content contains as much as one billion microorganisms. These are specialised in different areas such as the production of water-soluble vitamins, amino acids contained in proteins and fatty acids from which energy is derived. It is estimated that up to 60 % of the horse’s body energy is extracted in its large intestine. A large proportion of energy is extracted through the decomposition of cellulose in plant fibres.

The balance of the different types of microorganisms in the large intestine is hugely important as disorders, if any, will affect the general well-being of the horse. Such disorders can for example be caused by inadequate feed rations (e.g. not enough fibres or excess starch), overfeeding, medication, stress or unsuitable drinking water.

Because the horse is designed to eat grass, it is important that most of the energy it needs is extracted in the large intestine – i.e. through the degradation of plant fibres. This creates a balance in the intestinal flora and stabilises bowel function.

Faeces
k13

When there is a sufficient amount of faeces in the rectum of the horse, its rectal reflex starts to work. A normal bowel movement consists of a number of easily decomposable faeces ‘balls’. Runny and smelly faeces should always be seen as a warning sign and may be an indication of a disturbance in the microflora of the large intestine.

Wetter faeces are often a sign that the horse has an increased loss of body fluid. It is important to replace any loss of fluid associated with faeces but this can sometimes prove a little difficult if the horse is reluctant to drink. If you think that your horse has not been getting enough water for a while then try KRAFFT MASH Sensitive. It is a supplementary feed for soaking that you can feed as wet as you want.

Also, by giving your horse ample rations of feed, you can increase the ability of your horse to store fluids containing electrolytes in its cecum and large intestine. The fluids found in the digestive system of the horse are bound to various types of particles with an ability to ‘retain’ fluid. It is important to provide the horse with fibres that bind fluids in the right way so that fluids lost through faeces and perspiration can quickly be replaced.