Can horses throw up, emesis, vomiting, heave, puke, hurl, chuck up – likely, we are all familiar with the sensation. Most mammals are able to vomit. You will have seen pets reconstitute their breakfast all over your kitchen floor after eating too fast. Or after sneaking something off the dinner table that isn’t meant for them.
Sharks can even throw up. A historic criminal case in Sydney, Australia. When a large tiger shark regurgitated a human arm in front of a crowd of repulsed aquarium visitors. But can your equine companion throw up?
Generally speaking, no horses cannot throw up. Biologically, they are prevented from regurgitating their food by their physiology and anatomy. The esophageal sphincter of horses is a lot stronger than in other animals. This means it is nearly impossible for them to open it under backward pressure from the stomach.
Horses have a weak gag reflex. So no amount of vile stable smells will make them retch, or invasive dental work. Finally, their anatomy itself makes vomiting incredibly difficult. The stomach and esophagus are joined at a lower angle than many other animals. So gravity prevents food and stomach acid from traveling up and out of the stomach.
When all put together, these conditions prevent vomiting. As it is a complex physiological event that requires close coordination in a sequence of reflexive movements. When you are about to throw up, the vocal cords lose, the larynx rises, the soft palate shifts to close off the trachea (the airway connecting the mouth to lungs).
Then, the diaphragm contracts downwards, loosening the pressure on the esophagus and the esophageal sphincter. The muscles of the abdominal wall then contract spasmodically, putting sudden pressure on the stomach, and the contents of the stomach are expelled through the sphincter.
They then travel through the esophagus, until they reach the mouth and leave the body. Just one anatomical or physiological alteration from the mammal ‘norm’ will disrupt this sequence, and prevent an animal from being sick, so when taking all of this horse anatomy information together, it is unsurprising that they are left unable to be sick.
Oh No, My Horse Has Been Sick – What Does This Mean And What Do I Do?
There have been a few reported cases of horse vomiting – although it is possible that these were the regurgitation of material they had been choking on or had been an esophageal blockage (and hence had never actually entered their stomach).
It is also possible that these houses may have passively regurgitated their food. If a horse is very ill, the esophageal muscles can go flaccid, leading to ingested food oozing from the nose and mouth. This is very different from the active process of vomiting, where multiple muscle groups need to be engaged in sequence.
If your house appears to have vomited, it is likely very poorly and requires veterinary attention as soon as possible. Remove all food from its reach, phone your emergency vet, and try to keep your horse calm until they arrive.
Why Have Horses Evolved To Not Throw Up?
Vomiting is a defensive action, used in order to protect an animal from anything toxic that it might have ingested, preventing illness and even death.
It seems like there would be no negatives to having the ability to vomit. So why can’t horses throw up – surely it would do them more good if they did have the ability? Really, we can’t yet answer this question, only speculate.
Presumably, at some point, it was more evolutionarily valuable for horses to retain food in the stomach than it was for them to have the ability to eject toxins.
Alternately, they may never have needed the ability to vomit, as they are grazing herbivores, that feed in small portions constantly through the day, and are fairly fussy about the plants that they consume.
Evolutionarily, it is totally possible that the number of horses taken out of the gene pool because they ingested toxins was never high enough to significantly influence the way that horses developed. Another theory is that the way horses run means that vomiting would happen too frequently to be beneficial.
The horse’s intestines move back and forth like a piston, which would induce vomiting in other animals. Perhaps horses developed a powerful esophageal sphincter to prevent excessive vomiting.
Do Horses Feel Nausea?
Despite not being able to be sick, horses can feel nauseated. Horses, just like other mammals, can experience nausea and motion sickness.
Nausea in horses can be caused by travel, grass sickness (a condition where parts of the involuntary nervous system are damaged, causing a variety of symptoms, the main one being gut paralysis), and ingesting toxic material. As they can’t vomit, they experience colic instead.
Colic is a veterinary term to describe abdominal pain, which can indicate a problem with the gut itself, or other organs within the abdomen. It can be caused by many factors, ranging from simple indigestion all the way to twisted intestines.
How To Tell If Your Horse Has Colic?
Colic is one of the most common causes of death in horses, but thankfully the prognosis is far better for a horse that develops colic than it used to be. To tell if your horse is suffering from nausea and colic, look for these symptoms:
- Mild cases might show lip curling, flank watching, pawing the ground, and restlessness.
- Moderate cases might show posturing to urinate frequently, lying on their side for a long period of time, lying down and getting back up frequently, as well as previously developed symptoms.
- Severe cases might show violent rolling, sweating, injuries from thrashing around, rapid breathing, in addition to previously discussed symptoms.
If your horse is showing signs of mild colic, try walking them (do not canter or trot) for no more than ten minutes. Should symptoms carry on for more than 30 minutes, contact your vet.
If your horse is showing moderate to severe symptoms, phone your vet immediately, as it is a potentially life-threatening disease.