You have probably read a million articles about how equine digestion works. You’ve also probably seen the illustrations showing the parts in detail. Have you ever looked at your horse however and wondered what exactly is where?
I present at a lot of seminars and nutrition is a favorite topic. I have discovered that if I use a fun way to engage the audience that I am able to teach this difficult concept at the same time. It starts with a trip to Home Depot. Yup, you read it right. Home Depot.
I begin by collecting items that represent each part of the horse’s digestive tract. I choose things that are similar in size, length & diameter to the various organs of the equine digestive tract. It’s an interesting exercise that ends up with 10 audience members standing around the lecture hall holding sections and signs. Of course the person holding the rectum usually wishes they had not raised their hand to volunteer.
I skip the mouth and pharynx as horse owners usually understand that’s where the digestion process begins. Instead, I start with the Esophagus where a 4-5 foot long section of a garden hose represents this part of the digestive tract.
The main function of the esophagus is to carry food to the stomach. There is a muscular ring, called the cardiac sphincter, that connects the stomach to the esophagus but I leave that off.
The next section of the equine digestive tract has two parts but it’s called the Fore Gut and includes the
Stomach & Small Intestine.
A 2-4 gallon gas can is fed through the “esophagus” hose and represents the Stomach, as a horses stomach is about this size and holds as much. The average sized horse (800 to 1,200 pounds (360 to 540 kg) has a 4 gallon stomach which works best when it contains about 2 gallons (7.6 L).
The equine stomach empties when 2/3 full, whether the acid and enzymes have completed their processing of the food or not. This is why smaller frequent feedings are the best approach to feeding a horse. The stomach empties (after as little as 30 minutes) into the second part of the fore gut.
The small intestine is the major digestive organ for the horse and secretes enzymes for breaking down the food. It takes between 30 to 90 minutes for food to pass through the small intestine and for most nutrients to be absorbed into the bloodstream. This is the section where proteins, simple carbohydrate, fats, and vitamins A, D, and E are digested. From here any remaining feedstuffs move into the Hind Gut section.
The Hind Gut includes 5 organs the cecum, the large colon, the small colon, the rectum and the anus.
A plastic garbage bag (or bags) about 4 feet long, stuffed with hay and shaped with tape to be 30cm in diameter represents the Cecum. It is in the cecum that undigested food from the small intestine, such as hay and grass, is broken down with cellulose plant fiber digesting bacteria and microbes in a process called fermentation. Vitamins and fatty acids that result from the fermentation process are digested here. Food will remain in the cecum for up to seven hours then moves on to the large colon.
The main purpose of the large colon is to absorb carbohydrates, which were broken down from cellulose in the cecum. A 10-12 foot long dryer hose does the job of representing the Large Colon in our model.
The dryer hose is looped and turned with many folds representing the “flextures” of the large colon. The “flextures” in our dryer vent model are held in place with plastic ties.
The twists and turns of the cecum and large colon can trap food and are the reason that these areas are a common place for colic.
The next section of the equine digestive tract is the Small Colon which is 10 to 12 feet (3.0 to 3.7 m) in length and holds only 5 gallons (19 L). Another section of our 100’ garden hose represents this important organ.
Most of the nutrients have been digested by the time food reaches the small colon and what’s left is usually considered indigestible. It is however the area where the majority of water in the horse’s diet is absorbed, and is the place where fecal balls are formed. Considering how far the food and moisture has had to travel to reach this point it becomes clear how important water consumption is to a horse.
The Rectum is about 1 foot (30 cm) long. In our model the since the garden hose represents both the rectum and the small intestine, a small section is marked off with tape from the previous section (the small colon) to illustrate this organ. The rectum is primarily a place for the storage of the fecal balls that were formed in the small colon. As all horse owners know the fecal balls are expelled through the anus but I usually skip this part of the digestive tract in my model as I would never ask a volunteer to be the manure expelling anus!
If the length and complexity of the horse’s digestive tract does not amaze you consider this….
It All Fits Into a 32 Gallon large trashcan; which is about the size of the average horses’ barrel.
This entire digestive process can take 3 days from start to finish. It travels ~100 feet and involves an intricate balance of acids, enzymes and bacteria to complete the transition of feedstuffs to nutrients to manure for your horse.
So the next time you feed your horse think of Home Depot. Feed multiple small, fiber filled meals with plenty of water to allow the horse (and its garden hoses, gas can, trash bag, dryer hose and trash can) time to digest!
Here is a link to a video I created to help you visualize the model. Enjoy!
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©2013 The Equine Nutrition Nerd