How much of a horse enthusiast would someone be to look up for its number of stomachs, on the internet? Well, that’s up to you to decide but yes! This is an article on the anatomy and physiology of a horse’s gut. Now, before delving deep into the architecture of the equine digestive system, let’s sequentially evaluate certain aspects first.
Horse Alimentary System – The “Big Picture”
In order to have a basic idea of the size and volume of a horse’s gut, imagine a garden hose that is a hundred feet in length, gather it, and make a concentrated horse belly-sized ball. The two ends make up the proximal (esophagus) and distal (rectum) portions, while the middle aspect is the chunk of its abdomen.
An average adult size horse weighs between 380 kg and 1,000 kg. The gut volume comprises almost 60-70% of its gross weight. All this certainly gives us a pretty neat picture of the gut size of a horse.
Just like most of the livestock species, the horse is classified as an herbivore of course, but a non-ruminant one. What does that mean?
A non-ruminant species means having a single stomach. Unlike most of the barn livestock that are actually ruminants (having more than one stomach), horses have only one stomach, and hence, are classified as non-ruminants.
This might be surprising for some, but it is true; horses have a single stomach. Another fact worth mentioning is that horses classify as monogastric (having simple stomachs), unlike dogs, cats, or even humans. A cow, on the other hand, has a compartmentalized stomach that has 4 partitions. In short, a horse’s stomach is quite similar to that of human beings.
The Anatomy Of A Horse’s Stomach
The size of the horse’s stomach, as compared to the rest of the gut is comparatively small and can hold almost 9 to 10 liters of fluid volume. The horse is accustomed to eating smaller meals and more often (which is actually a very healthy diet plan).
However, domestication has caused a major change in the feeding habits of a horse. They are expected to eat larger amounts of feed with lesser frequency, subject to satiety. All this immensely undermines the digestive and absorptive capabilities of the horse. To overcome this, horses are given artificial pepsin along with the regular horse grain to allow quick breakdown and absorption of food. On average, it takes almost 24 hours for a horse to clear the entire digestive tract.
The horse stomach has 3 main areas; the saccus caecus, fundus, and pyloric region.
Saccus Caecus Region
Situated at the junction of the esophagus and stomach, as soon as the food enters this region it comes into contact with hydrochloric acid and pepsin. Pepsin is a protein-digesting enzyme that works at a low pH (2-3) and hydrochloric acid provides this optimum pH. Apart from that, hydrochloric acid also breaks down the larger food particles into simple monomers.
The body of the stomach is where the fundus is. It has extensive surface area due to in-folding (rugae) which greatly increases the efficient contact of food particles with the enzymes responsible to digest them. 90% of the food digestion takes place in the fundus region of a horse’s stomach.
Apart from this, the fermenting bacteria reside here and are involved in the fermentation process of the digested food particles into absorptive constituents. There must, however, be a balance between acid digestion and fermentation as fermentation proceeds at a pH of 4-5.
The final segment of the stomach is a pyloric region where the pH again drops to almost 2. This pH drop completely eliminates the fermentation of lacto-bacteria and initiates proteolytic activity. The proteolytic activity here is almost 10 times more potent than in the fundus region. Ill patterns of horse feeding may cause the stomach at the pyloric region to ulcerate due to excess abnormal pepsin and HCl secretion.
Why A Single Stomach?
The next big question arises why would a sturdy one-ton animal have only a single stomach? To answer this, we first describe what would be the benefit of multiple stomachs. Ruminants have compartmentalized stomachs with multiple partitions. This is due to the fact that they have to store large amounts of food within the stomach and gradually break it down. This process of discontinuous feeding helps a ruminant to have stores of food for unforeseen situations.
A horse, on the other hand, is not equipped to store large quantities of food because of its tendency to catabolize it rapidly and provide the energy necessary for its physique designed to perform hard labor. A single stomach would mean a shorter pathway for digestion and a lesser time to absorb nutrients into the bloodstream. And that is also why you should be glad your horse has a one-piece stomach.
The horse gut can be broadly divided into 2 segments. The foregut segment digests the food while the hindgut region absorbs and ferments the digested food monomers. The stomach plays the most important role in the digestive system, aka breaking down the complex material of food into a simpler form. Such anatomy makes the equine digestive system unique from the other herbivores.
Comparing Ruminants And Non-Ruminants
Having more than one stomach has its pros and cons but a single stomach doesn’t have to lag behind as well. Below a comparison is made between a horse and cow to differentiate between physiological aspects of single and multiple stomachs;
|Single Stomach Non-ruminant such as Horse||Multiple Stomach Ruminant such as Cow|
|Simpler digestive system not capable of storing for long periods of time||Complex multi-gastric setup designed to store a lot of food at a particular time|
|Specialized to match the physique of a horse and the work it is put in||Explains the reason why ruminants are not designed for hard labor|
|Purely digestive in function and has less cellulase activity||Digestive as well as absorptive in nature due to presence of higher cellulase activity|
The equine digestive system is extremely sensitive and prone to immense disorders. Diet variations affect the bacterial population in the intestine. Feeding your horse with meals in lesser quantity and more frequently can guarantee the best gut health making your horse run at maximum potential.
FAQs Regarding Stomachs Of A Horse
Ruminant animals are those animals that have stomachs compartmentalized into four partitions. The horse only has one stomach and thus it does not fall under the definition of a ruminant animal. Not only do horses have single stomachs, but their stomachs also comprise of simple anatomy containing only 3 regions. These are saccus caecus, fundic and pyloric regions. On the other hand, ruminants have much complex stomach anatomy designed mainly to store food apart from only digesting it.
All those animals that have more than a single stomach compartment are either ruminants or camelids. Ruminants have 4 while camelids have 3 compartments to their stomach. These animals have the ability to re-churn the swallowed food back into the mouth for further fermentation. On the other hand, animals such as horses are non-ruminants and their stomachs work much like those of humans.
The horse’s alimentary canal comprises the oral cavity, esophagus, stomach, small intestine, large intestine (containing large colon and small colon), and rectum. Much like the anatomy of the human digestive tract, a horse also contains certain glands associated with the G.I tract which include the liver, salivary glands, and pancreas.
Most herbivorous animals are ruminants (having more than one stomach). Horse being a herbivore, it is expected that it will also be a ruminant, but on the contrary to popular belief, it has only one stomach. The reason behind such anatomy is that horses are equipped as robust and agile work machines requiring adequate and spontaneous replenishment of nutrients. Having a single stomach quickens the energy absorptive process and allows the horse to complete digestion as soon as possible.
Feeding a horse with fewer grains and roughage at a time but increasing meal frequency certainly proves beneficial for the animal. Lesser quantity and better quality feed would mean optimum digestion and better absorption into the blood. On the other hand, feeding horses with a massive amount of feed at a time can result in numerous G.I. disorders such as colic disease and ulceration. Discontinuous feeding certainly has an edge over continuous feeding for non-ruminant herbivores as horses.
Much in Common…
We can arrive at the conclusion that horses have much in common with humans as regards the gut. Although, not having the same size of the gut, but we surely have the same number of stomachs (seriously, just one). And that seems to work perfectly fine for both horses and us.