About Your Horse’s Digestive System
To understand your horse’s nutritional requirements, you’ll need to have a good grasp of how and why his digestive system works in the way that it does.
In this article, we take a look at how the horse’s digestive system functions and how you can manage your horse’s feeding regime to keep him healthy and performing to his optimum.
The horse’s digestive system
The equine digestive system comprises:
- Mouth and teeth
- Small intestine
- Large intestine
- Large colon
- Small colon, rectum, and anus
Each part of the horse’s digestive system plays a different role in processing the animal’s food and water intake.
Mouth and teeth
The horse uses his tactile lips to grasp items of food. The tongue and teeth then chew and grind the food into a pulpy paste ready for removal to the next part of the digestive system.
When the horse chews forage such as hay or grass, he uses a long, sweeping jaw action. When eating hard feed, the chewing action is shorter and less sweeping.
Horses at year-round pasture tend to wear their teeth down naturally, whereas horses whose time at grass is more limited are prone to developing sharp hooks on their teeth.
That’s why a visit from a good equine dentist is essential to correct any uneven wear on the teeth and keep them in good order. Horses whose teeth are not properly maintained can develop painful ulcers on the tongue and inside of the cheeks, leading to eating problems and bitting issues.
The esophagus is a muscular tube of around 4.9 feet in length that transports food from the horse’s mouth to his stomach.
Because of the length of the esophagus, the horse has little or no reflux ability and cannot vomit. That means unchewed lumps of food can become lodged there, causing choke. To reduce the risk of choke, keep your horse’s teeth well-maintained, and add chaff or chop to the feed to slow the eating process and discourage the horse from bolting down the food.
The horse’s stomach is tiny relative to the size of the animal and accounts for only 10% of the digestive system’s capacity.
Horses are natural trickle feeders, continually eating small amounts of forage. Therefore, asking your horse to eat several large portions of grain once or twice a day goes against what his digestive system has evolved to do.
The horse’s stomach takes roughly 15 minutes to pass a large meal through into the next part of the digestive system. However, if the horse has fasted, clearance time can be up to 24 hours.
From the stomach, food passes into the small intestine, which accounts for roughly 28% of the horses’ whole digestive tract.
Most of the digestive process occurs in this part of the digestive system.
Here, nutrients are absorbed through the walls of the small intestine to be carried around the body by the bloodstream to wherever they are needed.
Almost 30 to 60% of carbohydrate digestion and nearly all absorption of amino acids takes place in the small intestine.
Feed processing practices, such as micronization, increase the digestibility of grains in the small intestine to roughly 90%. That reduces the burden on the large intestine, reducing the risk of overloading the horse’s digestive system and thus preventing incidences of conditions such as acidosis, colic, and laminitis.
Food typically takes three to four hours to pass through the small intestine. That allows the enzymes in the horse’s gut time to process proteins, fats, and starches, maximizing the small intestine’s digestive efficiency. Adding oil to the feed can also reduce the flow of food through the small intestine, improving digestibility and ensuring that your horse gains maximum nutrition from his diet.
Unlike cattle, horses do not have detoxifying bacteria in their gut that can deal with toxins. That makes horses highly susceptible to colic after eating moldy or spoiled feed because the toxins they contain will enter the intestine and be absorbed directly into the bloodstream.
The horse’s large intestine makes up 62% of the whole digestive system.
In the large intestine, digestion is mostly microbial rather than enzymatic. Plant fibers and undigested starches are broken down into volatile fatty acids that are absorbed through the gut wall.
The caecum is a blind sack, roughly four feet long with a capacity of up to eight gallons. The caecum works in a similar way to a cow’s rumen; microbes break down fibrous feed such as hay or grass.
The caecum has a major design flaw; its exit and entrance are both sited at the top. That can cause problems if the horse eats a lot of dry food without sufficient water or if the horse’s diet suddenly changes. In both cases, a compaction may occur at the lower end of the caecum, which is a common cause of colic.
It can take two to three weeks for the microbes in the caecum to adjust to a change in diet and re-establish normal function. That’s why it’s so important to introduce dietary changes over a prolonged period of one to two weeks.
Feed remains in the caecum for around seven hours to allow bacteria time to begin breaking it down by the process of fermentation.
In the horse’s large colon, the fermentation process continues.
Most of the nutrients created by microbial digestion are absorbed here, as well as B group vitamins that are produced by the bacteria, along with some trace minerals and phosphorous.
The colon has a “sacculated” construction, resembling a series of pouches. That design permits the digestion of large amounts of fiber, but it can also present a risk factor for colic because the pouches are prone to becoming twisted and filled with gases that are produced during the fermentation process.
It can take up to seven hours for food to reach the large colon, and it can remain there for up 48 to 65 hours.
Small colon, rectum, and anus
By the time the food has reached the small colon, most of the nutrients have been extracted from it. What’s left is waste matter that cannot be digested or used by the horse.
The small colon’s primary function is to extract moisture from the feed and return it to the body. That results in the formation of fecal balls, which are basically undigested and indigestible food. The fecal balls are passed through the rectum and expelled as manure through the anus.
From feed bowl/haynet to muck heap, the whole digestive process takes from between 36 and 72 hours to complete.
How to prevent digestive system upset
There are a number of ways to avoid upset to the horse’s digestive system.
Feed your horse little and often
This strategy imitates the horse’s natural feeding pattern and makes sure the digestive system is working properly by ensuring a constant movement of food.
Keep to a routine
A routine is important for horses. Any change in a horse’s daily schedule can lead to digestive upset. Be sure to feed your horse at the same time every day, and turn him out for the same number of hours daily if possible.
Introduce new feeds gradually
It can take up to two to three weeks for the microbes in the caecum to adjust to a new diet and return to normal function. If you are going to switch from one feed brand to another, for instance from timothy hay to alfalfa, you must do it slowly. Mix the two feeds for a week or so while gradually removing the old feed and increasing the new.
Monitor your horse’s environment
Keep an eye on your horse’s field! If an apple or oak tree is loaded with fruit or acorns, you should consider limiting your horse’s time out in that field.
When the first bloom of lush green grass appears in the spring and again in fall, introduce your horse to it gradually.
Devise a worming program and stick to it
A gut full of parasites can cause colic. But killing off too many parasites at once can also cause a digestive system upset.
It’s therefore essential to regularly worm all horses that are turned out on the same pasture at the same time.
Keep up a good worming program and ask your vet practice to take fecal egg counts for you once a year so that you can be sure your worming regime is effective.
Maintain your horse’s teeth properly
When horses’ teeth are left unattended, they can develop sharp points that can cause mouth ulcers and injury to the tongue.
Also, you want your horse to have the greatest grinding surface available so that he can get his food into the best digestible condition possible before sending it to his stomach. It is therefore recommended that your horse’s teeth are checked every six to nine months by a qualified equine dentist.
Lock your feed room door!
Keep your feed in containers that horses can’t break into should the feed room door be left open.
Gorging on any feedstuff can give horses colic. A serious grain-overload colic could be followed by laminitis, all of which is avoidable if the feed room door is kept locked.
Store feed in rodent-proof containers
Keep your hard feed in waterproof, rodent-proof bins. Rats and mice can carry diseases such as Lyme disease that is spread via their urine.
Also, damp food will quickly spoil, potentially exposing your horse to a nasty bout of colic.
Make fresh water freely available
Horses need clean, fresh water available at all times. Don’t forget to keep the water tub in the field clean and filled. Also, your horse’s stable should have at least one automatic waterer or large bucket of fresh water available whenever your horse is stabled.
Soak feeds correctly
It’s vital that sugar beet and other soakable feeds are soaked for the requisite length of time. Sugar beet that isn’t soaked for long enough before being fed to your horse will continue to swell and expand in the horse’s gut, potentially leading to impaction and colic.
Now that you understand the mechanics of the horse’s digestive system, you can see how important it is to feed him correctly.
Correct feeding will ensure that everything works harmoniously and without disruption. Your horse will derive the full benefit of the expensive feed you’re giving him without the risk of colic, gastric ulcers, and other digestive system problems.
If your horse had digestive system problems in the past, how did you resolve them, and what steps did you take to prevent the issues recurring in the future?
Tell us your horse’s story in the comments box below!
- How to Feed for the Dressage Arena
- About Equine Gastric Ulcer Syndrome (EGUS)
- How to Quarantine Your Horse
- How to Safely Transport Your Horse