Monogastric animals have a stomach that has a single compartment. Humans have a monogastric stomach, as do pigs, chickens, rabbits and horses.
Animals with a monogastric digestive tract can get cellulose from their diet and digest some of it. However, unlike ruminants, which are animals with more than one stomach compartment, gathering energy from cellulose is not as efficient. There is symbiotic bacteria in the stomach that aids in cellulose digestion. Anatomical adaption over time is what makes the partial digestion of cellulose possible.