Well this is a gross topic, but important to understand your horse’s health. I always knew from experience if a horse can vomit or not but I did some deeper digging into why.
So can a horse vomit? It’s nearly impossible for a Horse to vomit. A muscular valve called a sphincter leads to the stomach and it’s so strong in a horse that it works like a cut-off valve. This will not open and allow food from the stomach to go back up and out the esophagus.
There are times when it’s possible that a horse could vomit or do something similar to that, if you really want all the nitty gritty.
Why vomiting is rare in horses
Vomiting is difficult for the horse for several reasons. One is that the stomach is small and does not lie on the floor of the abdominal cavity.
The horse’s esophagus joins the stomach at a much lower angle than in many animals. Since the muscles of the equine lower esophageal sphincter are so much stronger than in other animals, it makes it impossible to open the valve under backward pressure from the stomach.
When the stomach is distended, as with gas, it presses against the valve in such a way that it holds it even more tightly closed.
Located deep within the rib cage, the horse’s stomach can’t be squeezed by the abdominal muscles. Also, the shape of their stomach is significantly more round “bent” compared to animals stomach which can vomit.
The real reason that horses can not vomit out of the mouth like is normally done, is because they have an extra long soft palate, which along with the strong sphincter, acts like a one way valve.
It stops food going down into the trachea and air getting into the esophagus.
When food does comes back up the wrong way it only allows it out through the nose, not into the mouth. Which is why you might see your horses with food coming out of their nose. Such as in the instance of grass sickness for example.
Also horses seem to have a weak vomiting reflex. The neural pathways that control that activity in other animals are poorly developed in horses.
Why were horses built without this ability
That’s a good question. We know how they can’t vomit. But we are not sure why they developed without the ability to.
Some have said it’s because they are trickle feeders. A horse was a wild animal that grazed all day long. Their muscles developed to promote the continual movement of digested food from the stomach through the rest of the digestive system.
One of the most popular beliefs is it’s basically so they don’t vomit when running.
A horse has to move to function properly—gut movement and circulation depend on it. Since horses are a prey animal, they use speed as a way to avoid danger. At high speed various symptoms “sync up”, including the diaphragm, which opens and closes like a bellow and operates the lungs without separate muscular effort.
So presumably this would affect the gastrointestinal tract too. Because they are flight animals, at a fast gallop the last thing they would need is for their food to able to come back up.
What does it mean if my horse does throw up
Vomiting may occur when the stomach is severely distended with food or gas. When it is stretched tightly, it may eradicate the valve-like fold. More pressure can be put on the stomach as the abdominal muscles contract.
The distension must be extreme to permit vomiting. At this point, the extreme pressure frequently leads to rupturing of the stomach walls.
This has given the impression that vomiting cannot occur in the horse without rupture of the stomach. This is not entirely true, as it is possible for the animal to vomit and be normal afterward.
Often, however the pressure is so great that the animal vomits and the rupture of the stomach occurs at the same time, leading to an infection of the lining of the abdomen called peritonitis. Unfortunately if this happens it is usually fatal to the animal.
After the stomach has ruptured, the animal will usually show considerable relief and appear to feel much better, temporarily. Once this rupture has happened, the animal will will no longer be able to vomit.
What animals can’t vomit? Horses can’t vomit, except for a few serious physical conditions that usually end up being fatal. Rats and Rabbits also lack the ability to vomit. Cattle can vomit but it is extremely rare.