Horses are designed to be grazers with regular intake of roughage. The horse requires a steady flow of acid for digestion, so a horse’s stomach produces acid 24 hours a day, 7 days a week, up to 9 gallons of acid fluid per day, even when not eating. In a natural high-roughage diet, the acid is buffered by both the feed and saliva. Since the horse’s stomach continually secretes acid, the horse needs to eat continuously to neutralize the acid.
The horse’s stomach is divided into two parts, and the bottom portion is glandular. It secretes acid and has a protective coating to keep it from being damaged by the acid. The top portion of the stomach is designed for mixing of the contents of the stomach and does not have as much protection from the acid.