The old saying you can lead a horse to water, but you cannot make them drink is literally true, but there are some things you can do to encourage drinking. Dehydration is a major cause of problems in horses and is commonly encountered in equine practice.  Although dehydration can be caused by many factors, colic is a common problem either causing or leading to dehydration. Various products have been added to the water to attempt to increase water consumption but until recently no studies had been performed to determine the most effective addition to encourage water consumption. 

The veterinarians at Washington State University performed a study to determine which additive encouraged water consumption. They used commercial sweet feed flavored electrolyte, peppermint extract flavored electrolyte, and apple flavored electrolyte. Results showed some evidence that commercial sweet feed and peppermint flavoring added to water did increase water consumption. The addition of commercial flavored sweet feed to the water was more effective than peppermint flavored water.  Interestingly, horses actually consumed less water after adding an apple flavored electrolyte solution to the water compared to drinking plain water.  So, if you have a horse that will not drink, adding a small amount of commercial sweet feed just to flavor the water may be helpful.