Is Softened Water Safe for Horses to Drink?

Is water softener block salt okay for horses. I bought some and it contains brine, and they told me it was okay. – CM, Illinois

Dear CM,
This was an interesting question that, quite truthfully, I had never thought about and couldn’t answer without some research. In general, you have to be very careful about any kind of “block” that you offer to horses, as they may contain other ingredients that can be harmful to horses. For example, horses are very susceptible to a common ingredient in livestock blocks called monensin, or Rumensin. It’s a growth-promoting agent in cattle that works in the rumen (which horses don’t have) and so is toxic to them. There are also really high protein livestock blocks, deer licks, and sweetened or flavored horse blocks, all of which I recommend you avoid.

To get back to water softener blocks, here’s what the Cargill website said:

“As with food considerations, water softening salts are not intended for human or animal feeding. The particle size is inappropriate for small animals. In addition, water softening salt may have additives that are inappropriate for animal feed.”

One of these additives is sodium hexametaphosphate, a surfactant, not something you want your horse eating. In addition, there are at least three different kinds of salt that can be used to soften water. One of them, rock salt, is only 95% sodium chloride. The remaining 5% is made up of “insoluble matter,” whatever that is. Finally, some water softeners are made of with potassium, not sodium, which could be deadly to a horse with HYPP (hyperkalemic periodic paralysis).

For these reasons, I recommend you stick with salt and trace mineralized salt that is specifically designed for use in horses and stay away from water softener salt, deicing salt, and blocks for other species. In fact, you may want to stay away from blocks altogether. Research has shown that horses may not be able to get all the salt and other minerals they need from a block–especially if they are sweating a lot from hard work or high temperatures–because blocks were made for the rougher tongues of cattle. I suggest you give your horse a smoother block specifically made for horses or provide loose salt.