Is my horse properly taking in, chewing and swallowing both forage and feed?
By observing your horse while eating hay, grass and feed, you may find that while he is taking in food he may not be actually chewing and/or swallowing it – this is especially common in older horses with poor dentition that may be quidding forages or dropping feed. The horse appears to be eating well, but in actuality the forage or feed is actually balling up in the cheeks and then being spit out by the horse.
Source: Purina Mills Equine Specialist