Use horse tack and horse feed in Rhode Island? What are you supplying as horse feed? As a grazing herbivore, horses nibble forage constantly.. As they chew, they secrete about 10 gallons of bicarbonate-rich, acid-buffering saliva everyday (protection for their gut). Horses shouldn’t go more than 4-6 hours without forage. Fasting longer than this time sets them up for gastric ulcers.