During the warm seasons, horses may have access to pastures with forage that contain 60 percent to 80 percent moisture which goes toward their daily water requirements. Winter feedstuffs such as grain and hay contain less than 15 percent moisture. According to Sarah L. Ralston, DVM at Rutgers University, resting adult horses who consume 1.5 percent of their body weight in dry feedstuffs will need a minimum of three to seven liters of water per 100 kilograms (220.5 pounds) of body weight a day. A typical 1,100-pound horse will consume four to 9 gallons. If fed only dry hay, water intake will double. Lactating mares and horses who are exercised will need to increase their water consumption by 50 percent to 200 percent.

Each horse is different but in general, mature horses at maintenance should consume between 10 to 15 gallons a day in winter. In addition to monitoring intake, you can do a simple hydration assessment on your horse.

“Feel the horse’s gums, check the capillary refill time (CRT) by pushing a finger against their gums and counting how long it takes for the tissue to go from a pale white color to its normal pink color, and pull their skin away from the body to judge how quickly it ‘snaps’ back into place,” said Laura Petroski-Rose, BMV&S, and Kentucky Equine Research staff veterinarian. “Normal parameters for these checks would be moist gums (not dry or tacky), CRT should be less than two seconds, and the skin should snap back into place immediately – about one second.”