Most of us know that horse’s can’t regurgitate food that they’ve swallowed. Some people claim they’ve seen their horse up-chuck the contents of their stomach. However, this is more likely to be ‘quidding’. Quidding is when a horse, usually one that can’t chew properly due to bad or missing teeth, drops a bolus of food instead of swallowing it. These soggy bird nest-like lumps aren’t coming from the horse’s stomach. Horses don't burp either. Again, some people claim their horses do. But, what they think of as burping may actually be windsucking - not all horses latch onto something to crib or windsuck. Some figure out how to swallow air without holding onto anything. In extreme cases where the horse appears to be regurgitating a frothy, food-bit filled mess, the horse isn’t regurgitating, but choking and needs immediate veterinary care.



So we’ve been told that horses can’t barf or burp. But why? The first part of the horse’s digestive system is similar to ours. We have teeth to chew food, we get it into a manageable lump and then we send it down our esophagus tube to the stomach. Behind the area we call the “Adam’s apple” are strong muscles that form the Upper Esophageal Sphincter. This is what you activate when you choose to swallow, and it’s also activated when you breathe, burp or sick up. There’s a similar band of muscles right where your esophagus enters your stomach called the Lower Esophageal (also called cardiac or gastroesophageal) Sphincter. We don’t have any control over that valve. It keeps the contents of your stomach from going back up your esophagus - usually.



Related: Saddle Up Series - Understanding Your Horse's Back

Related: Your Horse From the Ground Up - The Hindquarters

Related: Your Horse from the Ground Up - The Hoof



So you and your horse have both esophageal sphincters. The difference is in the lower one. If you eat something you shouldn’t have, overeat or drink or get a stomach bug, your brain tells your stomach to get rid of it. The stomach muscles start to contract, and while the lower sphincter is supposed to keep food from heading back up your esophagus, the esophagus relaxes and the tight valve muscles become slack enough to allow your stomach to send the unwanted contents up and out. In horses, however, the muscles that make up the lower sphincter are very strong and just don’t relax. If a horse eats something it shouldn’t or gets sick, the contents of the stomach will stay where they were put. A horse’s esophagus isn’t a vertical pipe like ours is either, and the angle where it joins to the stomach prevents the valve from opening when the stomach is very full.



This muscular valve is so strong that a horse’s stomach will rupture before the valve relaxes. That is why, very occasionally, a horse does seem to barf. However, by that time, the horse is almost dead, because the stomach is so damaged.



This only answers the mechanics of “why” of course. Apparently rats and rabbits can’t barf either. What purpose does not barfing serve? The answer to that ‘why’ I have not been able to answer.