Horses’ have one of the most complex, sensitive, and convoluted digestive systems of any livestock. Almost all mammals have stomachs, except for a small handful of evolutionary anomalies, but how many stomachs does a horse have? As trickle grazers, who are also flight animals, the horse’s stomachs and digestive systems have evolved to have some very unique characteristics.
All life on earth requires energy to perform the functions of living, i.e., growing, moving, reproducing, thinking, etc. Plants are primary producers that gain their energy by capturing and utilizing solar energy. The remaining organisms must consume plant matter directly, as is the case with herbivores, or indirectly like carnivores which eat herbivores and other animals.
Horses have a non-ruminant monogastric digestive system. Thus, horses only have one stomach. Horses can quickly graze large areas but are not as efficient at extracting energy from the food as ruminants that chew the cud. Cows and other ruminants have complex multichambered stomachs. The stomach is an acid-secreting sac that attaches to the distal end of the esophagus and precedes the small intestines, other parts of the gastrointestinal tract, and accessory organs. Almost all vertebrates (animals with a backbone) have a stomach, except for the non-conformist platypus.
Digestive Anatomy Of A Horse
Horses are non-ruminant herbivores, meaning they eat mainly plant material. The horse’s gastrointestinal tract consists of the mouth, esophagus, stomach, small intestine, and the highly developed large intestine composed of the caecum, large colon, small colon, and rectum
The Mouth
Anatomical features of the mouth include the teeth, tongue, and salivary glands. Digestion of feeds begins when food enters the mouth. The horse chews reducing feed particle size and mixing it with saliva to begin the digestive process. Saliva acts as a lubricant to provide easier passage through the esophagus and buffers acid in the stomach. Once swallowed the bolus of feed moves from the esophagus to the stomach.
The Stomach
The stomach of the horse is the smallest unit of the digestive tract with a capacity of approximately 2-4 gallons, comprising around 10% of the total volume of the horse’s digestive tract. The horse has the smallest stomach in relation to the body size of all domestic animals. Due to the small capacity, smaller, frequent meals are recommended. The stomach’s main functions include mixing, storage, and controlled release of feed into the small intestine; and secretion of pepsin to begin protein digestion.
Small Intestine
The horse’s small intestine is approximately 70 feet long, comprising 30% of the total digestive system. The passage of feed through the horse’s small intestine is rapid, moving at approximately 1 foot/min and delivering the digesta to the cecum in as little as 45 minutes after a meal. volume of feed consumed and rate of passage affect digestion and absorption of nutrients – larger volume and increased rate of passage will decrease digestion and absorption
The digestion of oils and protein is extensive in the small intestine. The digestion of starch can often be incomplete due to the starch present in cereal grains being protected by the grains’ seed coat. If starch is not digested in the small intestine it will be delivered to the hindgut where it will be rapidly fermented by bacteria, causing lactic acid production and accumulation, hindgut acidosis, and diseases such as colic, metabolic acidosis, and laminitis/founder.
Hindgut
The hindgut of the horse comprises the cecum, large colon, small colon, and rectum. The cecum consists of 12-15% of tract capacity and the colon 40-50% of tract capacity. The major functions of the hindgut are the microbial digestion (fermentation) of dietary fiber (structural carbohydrates primarily from forages in the horse’s diet). Important end-products of the fermentation are volatile fatty acids (acetic, propionic, and butyric) which can serve as an energy source for horses fed mostly forages such as pasture or hay. Fermentation also produces methane, carbon dioxide, and water, as well as most of the B-vitamins and some amino acids. Another function of the hindgut is water reabsorption.
Why Do Horses Sleep Standing Up While Many Other Species Do Not
This is somewhat of a myth. Horses can get a lot of sleep while standing up, but they lie down when they require REM sleep. Typically, the amount of REM sleep they require is very small, so they don’t need to lie down often. However, many horses lie down just because they feel comfortable or want to do so.
The reason horses can sleep while standing for most of their sleep cycle is because it allows them to quickly escape an attack by a predator without having to waste time standing up (which can be a slow process compared to a predator attack). The method by which horses stand while sleeping is called the “stay apparatus,” and it’s a system of ligaments and tendons that keep them upright with relative ease.
How Many Stomachs Does A Horse Have
People often wonder how many stomachs does a horse have, but the horse is a non-ruminant herbivore. Non-ruminant means that horses do not have multi-compartmented stomachs as cattle do. Instead, the horse has a simple stomach that works much like a human’s. Herbivore means that horses live on a diet of plant material. The equine digestive tract is unique in that it digests portions of its feeds enzymatically first in the foregut and ferments in the hindgut. The horse’s digestive system really should be thought of as being in two sections. The first section has similarities to the pre-caecal digestive system of a monogastric animal such as the dog, man or pig. The second section is more like the rumen of a cow.
This has profound effects on the way we need to think about feeding the horses in our care. However, the horse is neither a dog nor a ruminant or even a direct combination of both. It is unique and needs to be considered as such. The cow benefits by having the microbial breakdown of fibrous food at the start of the GIT (gastrointestinal tract) and nutrient absorption can then take place along the entire intestine. Dietary protein is not utilised efficiently because the microbial fermentation breaks down protein plus some carbohydrate. In the horse unlike in the ruminant the microbial fermentation occurs after the ‘monogastric’ like section rather than before. This has a great impact on how we should feed a horse and explains in part why the horse and cow differ so much in their nutritional efficiencies and requirements.
Functions
The stomach is an important endocrine organ that produces a variety of peptide hormones that are essential to enteric and non-enteric physiology. It also plays a motility role, functioning as a pump, and is divided into two main sections, the antrum and pylorus. In this article, we will explore the functions of the stomach, including its role in pathologic states.
The stomach is not directly involved in the absorption of nutrients, but is involved in the absorption of certain substances, such as alcohol and aspirin. Vitamin B12 is absorbed distally in the digestive tract by the enterocytes in the terminal ileum. Several other substances, such as bile and digestive enzymes, are absorbed through the stomach. The stomach’s acidic environment allows these substances to pass through the intestine.
The mucosa lining the stomach is lined primarily with surface mucus cells. Mucus is secreted by these cells to protect the intestine from the acidic environment produced in the stomach. The stomach is lined with specialized cells called goblet cells, which secrete mucus. These cells produce hydrochloric acid and an enzyme known as Intrinsic factor. The mucus layer also protects the body from harmful bacteria and toxins.
Upon bolus entrance into the stomach, liquids enter the esophagus. Gravity causes the food to fall to the lower end of the esophagus, which is the site of further digestion and absorption. This process takes approximately 10 seconds. Once the food bolus reaches the stomach, the lower esophageal sphincter relaxes. The bolus then passes into the stomach, where it is digested and removed.
Size
The size of a horse’s stomach is one of the first things to understand when feeding a horse. A horse’s stomach is relatively small compared to its entire digestive tract, holding between three and five gallons of food. It is divided into two regions, the glandular and non-glandular. It is the latter portion of the stomach that contains the digestive juices that break down food. Here’s a photo that demonstrates how the horse stomach looks.
The stomach of a horse is a small and inelastic organ that holds approximately 8 litres of digesta. Because of this, it is advisable to feed horses frequently and in small quantities. You should not feed a full grown horse more than two kilograms of feed at a single meal. A large meal will cause abdominal pain, colic, and may even rupture the stomach. To avoid this problem, feed your horse two or three small meals throughout the day.
The upper part of the stomach contains the glandular region, which produces various secretions, including hydrochloric acid and peptidases that break down proteins. A horse’s GIT also undergoes minimal microbial digestion in the gastric compartment. Horses evolved under grazing conditions, so their stomachs are relatively small compared to other animals’. In addition to producing hydrochloric acid, the stomach secretes bicarbonate, mucus, and mucus to protect itself.
Sub-divisions
A horse has one stomach, similar to ours, which works much like a human’s. This stomach is a non-ruminant herbivore and only makes up 10% of the total digestive system’s volume. Compared to our four-chambered gastrointestinal system, a horse’s stomach is much smaller, only about nine to fifteen liters. The stomach also helps the horse digest food, as the horse eats small quantities of roughages and the passage time will depend on the method of feeding.
The horse’s stomach contains around two to four gallons of material. This is equivalent to eight cartons of milk. The stomach’s functions include mixing and storing food, and slowly releasing the food into the small intestine. Since a horse has one stomach, it cannot store large amounts of food, and must convert it into energy as quickly as possible. A photo taken from Rutgers University shows the digestive system of a horse.
The digestive system of a horse is interesting. A horse has a single stomach, and its digestion is not as efficient as a ruminant’s. It has a single large chamber in its colon, known as the cecum, where fiber digestion occurs. Horses use bacteria and protozoa to break down fiber. Unlike other animals, however, horses cannot digest the cellulose found in vegetables. Other animals can, and do, digest it using stronger acids. Raw vegetables, however, are less digestible than cooked or meat-based foods.
Can A Horse Vomit
A horse cannot vomit, which means that everything a horse ingests must pass through the entire digestive tract before being eliminated via the anus. A horse cannot vomit because:
- The gastroesophageal sphincter is extremely strong and highly resistant to opening under backflow pressure.
- The gastroesophageal sphincter in horses is positioned much lower than in animals that can vomit. When the stomach is enlarged and bloated by gas or the stomach contents, the stomach “folds” against the gastroesophageal sphincter preventing it from opening.
- The horse’s stomach is located deep in the abdominal cavity and experiences minimal squeezing by the abdominal muscles.
- Horses have a weak gag reflex and cannot reverse the peristalsis of their esophageal muscles.
The mechanism behind the inability to vomit in horses is relatively simple. Horses’ stomachs produce a gastric liquid with a pH of 2.72. The esophagus lacks a protective mucus coating, while the walls of the stomach are very strong and the heart has a tight sphincter. Therefore, gastric acid is not released backward through the esophagus, and food cannot travel backward. The stomach cannot throw up a large amount of food while running, and this liquid cannot travel back to the mouth.
The main problem with the inability to vomit in horses is that it can lead to death from a blocked stomach. Even though horses eat small amounts at a time, they are highly selective when choosing what to eat. They are also unlikely to ingest poisons because their stomachs are so small. If the cause is a food-related illness, the vet can use laxatives and mineral oil to aid digestion. The key is to consult a veterinarian immediately to ensure a horse’s wellbeing.
One of the most common causes of inability to vomit in horses is a colic condition. If a horse has a colic condition, it may have a blocked esophagus. If not treated immediately, a horse may become dehydrated and die. This condition is often a sign of an underlying problem, such as a stomach bacterial infection or a blocked esophagus.
Symptoms
During strenuous exercise, the horse’s stomach is under intense pressure. This compression pushes acid from the glandular portion of the stomach up to the nonglandular region, where it damages the intestinal cells that don’t have natural defenses. The result is ulcers in the nonglandular region of the stomach, similar to lesions in the human digestive system that can cause heartburn and gastric reflux disease. This can cause upper GI pain during exercise.
Gastric impaction in horses can occur due to improper feeding and poor-quality feed. Another cause is obstruction at the pylorus. Some horses with dental abnormalities cannot chew hay properly and may develop gastric impactions as a secondary complication of another intestinal lesion. Other signs of gastric impaction include feed material in the nares and difficulty passing a nasogastric tube. In either case, an ultrasound or endoscopic visualization of the impacted feed material can confirm the diagnosis.
While antacids may not work for ulcers in horses, some treatments are better than none. An antacid, for example, neutralizes the gastric acid and lowers its pH. Antibiotics, in contrast, do not cure the problem. The treatment of gastric ulcers depends on the cause of the condition and a combination of treatments. The use of an anti-inflammatory drug or a NSAID like firocoxib may be necessary for certain horses.
Do Not Forget!
One question that may seem confusing is, “How many stomachs does a horse have?” The answer depends on the animal’s feeding habits and how it is fed. Horses are herbivores, primarily feeding on grasses and other plant materials. They do not have rumen, which is the digestive system of cows and sheep. Instead, horses have a single stomach, which allows them to digest smaller portions of their food at a time. While this is quite interesting, it also means that a horse’s digestive system isn’t as efficient as a human’s.
The horse stomach is unique from the other animals in the animal kingdom, and is much smaller than a human’s. It is only two to four gallons in volume and performs three major functions. Horses store food in their stomachs, which include breaking down large protein chains and neutralizing harmful substances. When a horse chews, the stomach movement helps break down food and mix the acid with the food.
While human digestive systems are similar to those of ruminants, horses have a single compartment stomach. Its digestive system is also more complex. Horses have two stomachs: the upper, smooth section, and the lower, rougher, glandular part. In addition to the upper and lower parts, the horse’s stomach contains a sphincter, which prevents food from passing back into the esophagus.