My horse covered me in green slime this morning. After watching him trying to consume his breakfast faster than the speed of light, I ended up standing under my horse’s elevated head, trying to get a hosepipe into his mouth so I could flush out the offending blockage of food.
It was one of those times that had me wondering, “Can horses vomit?” I was pretty sure they couldn’t but, if they could, this would be a prime time to do just that – just not all over me!
Although my horse did manage to launch a large quantity of green slime from his mouth, he wasn’t vomiting. It was a combination of whatever was blocking his digestive tract, mixed with the large volume of water I pumped down his throat.
A horse’s inability to vomit makes dealing with choking a lot more challenging in our equine companions than it does in ourselves or other animals, like dogs, for instance.
Like us, dogs vomit as a defense mechanism. The action removes toxic substances and other stomach contents that are causing discomfort.
Being able to vomit can be the difference between life and death, so why did the horse develop this potentially life-threatening inability?
As a prey animal, the horse relies on its flight instinct to stay alive.
Even if they’ve got a stomachful of fresh, green grass, horses can still run off into the great beyond and not experience any of the discomforts we might if we suddenly ran off halfway through Sunday lunch.
To understand why horses can’t vomit, we must first understand the complex physiological events that make up the vomiting process.
Before we throw up, our vocal cords close and the soft palate in our esophagus moves to close off our airways. The diaphragm then contracts, relieving some of the pressure on the lower esophageal sphincter (LES).
When the muscles in the stomach walls subsequently constrict, they put pressure on the stomach, encouraging emesis or vomiting to occur.
How the Horse’s Anatomy Makes Vomiting Impossible
Both humans and horses have an esophageal sphincter that acts as a kind of one-way valve, allowing food into our stomachs but preventing it from coming back up.
The difference is that should pressure build up in our gut, our lower esophageal sphincter will open up, allowing the stomach contents to pass through the esophagus and out of our mouths.
In horses, the LES is much stronger than in humans, making it virtually impossible for a horse to vomit, no matter how much pressure accumulates in its stomach.
While our abdominal muscles are positioned so that they can contract when we vomit, horses’ are located in their rib cage, making it almost impossible for them to “assist the vomiting process.”
Horses also have a weak vomiting reflex, probably because their anatomy makes vomiting so impossible.
The Dangers of Not Being Able to Vomit and How to Prevent Them
Vomiting is our natural defensive mechanism against toxic food and anything else we may eat that causes discomfort in the gastrointestinal tract.
Without that natural defense mechanism, horses are more likely to develop other issues such as colic, diarrhea, and, as we mentioned earlier, choking.
The only time a horse is likely to vomit is when excess food or gas causes extreme pressure in the stomach, rupturing the stomach walls and leading to a fatal infection.
Horse owners need to understand these problems so they can find effective ways to avoid them.
Choke, for example, is often caused by horses eating too fast and can, in many instances, be solved by simply adding plenty of fresh water to any concentrated feeds before offering them to your horse.
You can also help prevent choke by ensuring your horse has access to clean drinking water, feeding hay in a slow feeder, and adding smooth stones to the feed so he has to eat more slowly.
Should your horse begin to choke, you can try palpitating the esophagus to help break up the blockage or pouring warm water into the horse’s mouth or nose.
Never use mineral oil for this purpose, nor to try and alleviate the signs of colic, as it “could be aspirated into the lungs causing fatal pneumonia.”
Mineral supplements and probiotics can also help address any digestive issues occurring from an imbalance of nutrients. These can help calm a hot horse, reduce the frequency of gastric ulcers, and prevent signs of colic.
Even changing your feeding routine can boost your horse’s digestive system.
Horses are trickle feeders and their digestive systems have evolved to support this. They are designed to process constant amounts of food over long periods rather than large amounts in a short time.
Eating a bucketful of sweet feed, for instance, could place negative pressure on the gastrointestinal tract, potentially causing discomfort and muscle contractions.
The conscientious horse owner also needs to encourage normal behaviors.
Horses are flight animals and need regular exercise to maintain optimal health and prevent the build-up of gas. For a stabled horse, that means at least 20 minutes of exercise a day.
Treating problems like choke and colic can be stressful, expensive, and usually requires some level of veterinary care.
If you take immediate action to treat a colicky or choking horse, however, you could help prevent it from developing into a more urgent issue.
If your horse is showing signs of colic, for example, you need to call a vet immediately, after which you should focus on keeping the horse moving.
Walking stimulates gut motility and helps prevent your horse from injuring himself by rolling.
Access to clean water is also crucial, as is checking their temperature and heart rate.
Find out everything you need to know about colic in this tutorial:
Horses may be able to cover you in green slime during a bout of choke, but they can’t vomit. They’re not the only ones either – several types of rodents, including those related to the guinea pig, lack the ability, as do frogs.
Thankfully, horses don’t throw up their entire stomachs and then pack them back in again as frogs do, but it also means vomiting is often associated with death in horses.
A horse that vomits is liable to have ruptured its stomach walls and, once that occurs, no treatment can save him.
The inability to vomit places extra pressure on horse owners who need to protect their animals against choke, colic, and toxic feed, while providing them with the mineral supplements necessary to maintain a healthy digestive system.