Why Does My Horse Dunk His Hay?

Q. My horse has a habit of dunking his hay in his water trough. He has done this for a long time, and I don’t know why he does it. Our climate is very hot in the summer, and it smells awful and attracts flies. I always worry it’s going to cause him to drink less water. Do you have any suggestions?

A. This is a habit that some horses develop, and we don’t really know why. The initial cause might be a problem such as dental pain or dusty hay causing nasal irritation. Then, over time, it becomes a habit or preference. Certainly, hay dunked in water first is slightly softer and less dusty. Some people also think horses will do this if they are suffering from gastric ulcers because scratchy hay might irritate the stomach lining. Contact your veterinarian to rule out any underlying medical conditions that might be the cause, especially if your horse starts dunking his hay suddenly.

If your horse has a clean bill of health and the hay dunking has been going on for some time, I suspect it has become a preference. The good news about water consumption and dunking hay is that your horse is taking in more water while eating than he would with dry hay. Although consuming dry hay often causes increased water consumption after eating, so overall water consumption might end up being about the same.

In hot weather, hay-filled water can become soupy and might ferment. Horses might find this unappetizing, and it can certainly result in decreased water consumption, which would be a concern if it leads to dehydration. Another concern is that consuming fermenting hay could cause gastrointestinal issues and colic. Therefore, it is important that you clean water troughs containing hay daily.

For hay dunkers I typically recommend having two sources of water: One close to the hay that they hopefully use for dunking and another further away that might stay cleaner. If the water bucket near the hay is small and gets filled with hay, it is more likely to ferment and attract flies than a larger bucket with more water. However, the larger the water source near the hay, the harder it will be to dump and clean daily.

A sieve can be a useful tool to keep on hand for scooping hay out of the bucket between cleanings. Do not leave hay that was in the water available for the horse to eat, as it might be fermented and unsafe. Throw it away in the same way you discard manure.

Having a hay dunker certainly causes more work in keeping water sources clean, but horses that do it seem to enjoy the process. Hopefully you can find a way to ensure your horse always has clean water available, minimize fly issues, and keep your horse happy.