Horses can easily get dehydrated during summer months. To prevent dehydration, follow these steps:
1) Clean water, and lots of it, is key: Scrub buckets out daily to assure the water remains palatable.
2) If your horse seems like he’s not drinking enough (10 to 12 gallons a day, minimum), increase his water intake.
3) You can soak his hay in water, which will add a gallon or two of water to his intake.
4) A watery bran mash with watermelon and apples will help increase his water intake
5) Add a tablespoon of salt to his feed to stimulate his thirst.