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Just The Basics About A Horse Digestive System

Horses have a very complex digestive system, and feeding your horse incorrectly can have serious or even fatal consequences. In this article we describe the horse digestive system and provide good advice on feeding your horse right to keep him healthy. Read on to learn more.

Top Advice For Feeding A Horse Correctly

Advice For Feeding A Horse Correctly

The main thing you should keep in mind when feeding your horse is that the most natural choices are the best. Horses do well with lots of fresh grass, clean free feed hay and a minimum of grains and processed feeds.

Why is a horse’s digestive system so sensitive?

Horses are herbivores, but unlike herbivore search such as cattle, goats and deer, they are not ruminants. This means that they do not chew a cud and then hold food in their rumen for hours re-chewing it and processing it extensively.

Instead, a horse’s digestive tract consists of a the mouth, teeth and esophagus, a very simple stomach, a small intestine and a large intestine. The stomach is quite small, so horses cannot eat large amounts of food at once. Instead, they are meant to continuously feed or graze on small amounts of roughage such as grass or hay.

This can be a challenge for many horse owners who do not have access to open pasture. Very often horses are forced to get most of their caloric needs met through grain and feed concentrates. Their access to pasture may be quite limited, and sometimes hay is in short supply and hard to come by.

The combination of these factors can make horse feeding very difficult, and can compromise your horse’s health and even his life.

How Can Improper Feeding Kill Your Horse?

Can Improper Feeding Kill Your Horse

Feed containing toxic materials such as mold or poisonous ingredients can cause a horse to develop colic or even to die. The reason for this is that, as non-ruminants, horses do not have the advantage enjoyed by cattle, goats, deer and other ruminant mammals.

These animals have an organ known as the rumen, which is part of the equine digestive system. This aspect of the digestive system of ruminants contains bacteria that detoxifies potentially dangerous materials before they can make their way into the small intestine.

Horses don’t have this, so if they ingest a toxic substance, it will go into the small intestine basically unchanged and be absorbed into the animal’s bloodstream without detoxification. This is why it’s so important to always feed your horse fresh hay and feedstuffs that are free of mold and other contaminants.

The Horse Digestive System

Why Is Equine Dental Health Important?

The mouth is the very first part of a horse’s digestive system. As with all animals, proper biting and chewing sets the stage for proper digestion. It’s important for horses to have good teeth because they need to grind their food up into little pieces in order to digest it properly.

Good chewing (mastication) assists in proper nutrient absorption. Furthermore, when food is properly chewed it is not a choking hazard and is less likely to cause impaction.

Chewing also stimulates the production of saliva, which is filled with enzymes that help to break food down for good digestion.

What Happens In The Horse’s Stomach?

What Happens In The Horse's Stomach

In the stomach, acids break food down and activate enzymes to begin protein digestion. Stomach acids are also instrumental in killing off potentially dangerous microorganisms which may be lurking in feed.

The enzyme known as pepsin works to digest proteins. Hydrochloric acid (HCl) is also added in the stomach to assist in breaking down solid particles.

How much can a horse’s stomach hold?

Even though most horses weigh about 1000 pounds, the typical horse stomach only holds about 4 gallons. Clearly the stomach is very small for the size of animal. It is also comparatively small alongside the remainder of the digestive tract.

This small stomach capacity makes it impossible for a horse to eat a large amount of feed at once. Furthermore, if a horse overeats or accidentally eats something that is toxic, it is not able to regurgitate the way other herbivores can, so a poisonous substance can quickly affect the horse because it is held in a small stomach, undiluted, and the horse has no way to get rid of it.

Another complication caused by the small size of a horse’s stomach is the fact that food is not held there for very long. When a horse’s stomach gets two thirds of the way full, it starts emptying into the small intestine. This happens even if the food has not been broken down sufficiently.

The way a horse is fed has an impact on how quickly food passes through the animal’s stomach. It can vary greatly. In some cases, feed may only stay in the horse’s stomach for about fifteen minutes.

Because food passes through the stomach so quickly, it may enter the small intestine without being fully processed by the digestive juices of the stomach. If a horse’s stomach remains empty for significant periods of time, the excess acid in the stomach is very likely to cause gastric ulcers, which are the most common digestive problem among horses.

What does the small intestine do?

Most of the nutrients in a horse’s feed are absorbed into the animal’s bloodstream through the small intestines. This includes:

  • Simple Carbohydrates
  • Essential Vitamins
  • Proteins
  • Fats

A horse’s small intestine consists of three parts:

  • Duodenum
  • Jejunum
  • Ilium

The entire small intestine is about 70 feet long and can hold about 11 gallons.

In the small intestine, bile (which comes from the liver) combines with enzymes (which come from the pancreas). These substances help to further break down and digest food.

It’s important to understand that unlike many other animals (and humans) a horse does not have a gallbladder. This means that bile is continuously flowing from the liver; therefore, a very slow and steady food supply is necessary to prevent damage to the interior of the small intestine caused by excess bile.

The amount of time that food spends in the small intestine is influenced by many different factors including:

  • Feed Type
  • Meal Size
  • Exercise

Feeds that are processed usually move through the small intestine quite quickly. This is partially because horses usually eat processed foods quite quickly. This rapid movement has a reductive impact on the amount of starch digested through the small intestine.

When food has gone through the digestive processes in the small intestines, the usable parts are absorbed through the walls of the small intestine and taken away through the horse’s bloodstream to supply nutrients to the animal’s cells.

Amino acid absorption and about 50% to 70% of the digestion of absorption of carbohydrates takes place in the small intestine. Even so, food is not present in the small intestine for a very long period of time. Usually it takes thirty minutes to an hour for food to make its way through the small intestine.

If you feed a lot of processed feeds, they move through the stomach and the small intestine too quickly. This results in a large amount of undigested starch ending up in the hindgut. This can cause an imbalance in your horse digestive system

What happens in the large intestine or hindgut?

equine digestive system
Source: theeloquentequine.com

The large intestine is known as the hindgut. Its components are the cecum, the large colon, the small colon and the rectum. Combined, the colon and the cecum can hold as much is 32 gallons of undigested fiber. This fibrous material ferments gradually over a period of two or three days.

Hindgut microbial fermentation is made possible by bacteria and protozoa in the billions in the hindgut. These tiny, friendly fauna breakdown fiber and tough elements of the grasses and forage that horses eat.

This process yields volatile fatty acids which are absorbed into a horse’s bloodstream to give the horse energy. Horses receiving a complete full forage diet will get as much is 70% of their energy from volatile fatty acids.

The cecum is about 4 feet long and it is a blind sack that can contain about 8 gallons. The cecum is best described as a microbial fermentation vat that performs a similar function to a ruminant herbivore’s rumen.

Undigested elements of feed that has made its way through the small intestine and into the cecum is broken down by microbes. Examples of this type of feed include forage such as grass and hay. These very fibrous foodstuffs cannot be broken down by the small intestine and will stay in the cecum for about seven hours.

In addition to breaking down grass, hay and other roughage, the cecum also produces proteins, fatty acids, B complex vitamins and vitamin K.

Keeping a healthy balance of microbes in the cecum is extremely important to a horse’s good overall health. It is the reason why you must change your horse’s diet very slowly and only when absolutely necessary.

Abrupt changes to the diet can badly disrupt and imbalance microbial colonies in the cecum. These friendly fauna need time to adapt and alter their chemical structure whenever new feedstuffs are introduced. Abrupt changes bring on colic caused by improper digestion of newly introduced foods.

Beyond the cecum are the large colon, the small colon and the rectum. The large colon holds 20 gallons or so of semi liquid materials, and it is approximately 11 feet long.

In the large colon, microbial digestion is continued, and the vast majority of the nutrients produced through microbial digestion are absorbed into the walls of the large colon.

There are many bends and twists in the 11 foot long large colon, so impaction is commonplace and is a form of colic.

The small colon has about a 5 gallon capacity and is also 11 feet long. Most water is absorbed through the walls of the small colon. Additionally, the formation of fecal balls takes place in the small colon.

All-in-all, food stays in a horse’s large intestine anywhere between thirty-five and sixty-five hours.

What if the hindgut is imbalanced?

If the hindgut is overloaded with undigested starch, it will throw the balance of friendly fauna off. Bacteria necessary to digest starch also produce lactic acid, and this increases the overall acidity of the hindgut.

This condition is called hindgut acidosis and results in toxins being released into the hindgut, and this can cause colic and even founder. Hindgut acidosis can also be the initiating cause of colonic ulcers.

In addition to these dramatic illnesses, you may notice every day behavioral issues with a horse suffering from an imbalance of hindgut microorganisms. These may include:

  • Overall Discomfort
  • Trouble Collecting
  • Trouble Bending
  • Irritability
  • Lethargy
  • Bloating
  • Malaise

It’s easy to see that a healthy, clean diet is the basis of good health for horses, as with most living beings. Even though providing that diet may sound daunting, you can simplify this task by keeping the basics in mind. Remember to keep your horse’s diet as natural as possible. Rely as much as you can on fresh grass and clean, mold free hay. Stay away from sweet feeds and processed feeds when you can, and confer with your veterinarian regularly to be sure you are providing your horse with the right diet.

Nicky Ellis
Nicky has been an editor at Horses & Foals since 2017. Horses have been in her life from her earliest memories, and she learned to ride a horse when she was 5. She is a mom of three who spends all her free time with her family and friends, her mare Joy, or just sipping her favorite cup of tea.


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