Client Resources: Articles

The Horse’s Stomach

When my phone rings at 6 AM I’m pretty sure it’s not a social call. “Dr J!”, she shouted, “I think we’re in trouble! You know my gelding Zeus? Well, he somehow got out of his stall last night and into the grain room, and it looks like he ate about half of that bag of sweet feed, and right now he’s not looking so good.” It’s the kind of call every equine veterinarian dreads. The morning schedule, including my own breakfast, was trashed, and as I drove to her farm my hope was that Zeus had gobbled all that grain within the last hour so that there might be a chance of saving him.

Why are horses so subject to problems like this? After all, last Thanksgiving I ate way too much, and was a bit uncomfortable for a couple of hours, but I didn’t have to call my doctor! One reason that horses can’t take this gorging is because they have unique stomachs.
Although they are herbivores, horses don’t have huge ruminant stomachs to break down fiber the way cows, sheep or goats do. In the horse the relatively small stomach churns the food, secretes acid and enzymes, and moves the food on down to the small and finally the large intestine where the real fiber digestion happens. Although the stomach doesn’t hold food long, it is the site for some real problems.

Most people have heard that horses can’t vomit. This is true for two reasons. The horse has a very strong sphincter muscle at the entrance to the stomach. It acts as a one way valve and won’t permit food to go back up. Vomiting is also prevented by an abrupt turn of the esophagus at the stomach entrance. This turn gets kinked when the stomach is full. Throwing up is no fun, but we all know how much better we feel when it’s over. For horses this inability to vomit is not only extremely painful, it can be fatal.

Stomach issues usually arise when horses are fed inappropriately. Horses are grazers, and do best when eating small quantities all the time. Because the stomach size is limited, huge meals or just heavy grain feeding twice a day can bring trouble.

Zeus, the Houdini horse, hadn’t eaten for hours, and while he was waiting for someone to get to the barn in the morning, he fiddled with the latch to his stall door until it opened, and he found his way to the grain room. He chowed down so fast his overloaded stomach couldn’t empty. His inability to vomit meant a very real possibility of it rupturing. This would have meant certain death if the stomach contents had spilled into the abdominal cavity. In this case we were able to prevent that from happening, but it was needless agony for the horse and a large, unanticipated vet bill for the owner.

An earlier article in this series suggests three barriers to keep horses from getting into this situation. These are the stall door, the grain room door, and the grain container. All three should be secure. Every year our practice gets at least a dozen calls from clients whose horses have gotten into the grain and pigged out.

Here are some quick rules for keeping all stomach problems to a minimum. In most cases roughage should be available 24/7. This is actually the best way to prevent stomach ulcers as well. Grain should be considered a supplement and never the main part of the diet. Any feed changes such as grain type or access to green grass in the spring should be made gradually.

The word colic means belly pain, and the stomach is just one place it can happen. Colic that originates here is misery for horses, and it is mostly preventable by good feed feeding practices.


David A. Jefferson, DVM

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