Some animals, such as termites, cows, and deer, have evolved symbiotic relationships with bacteria and other microorganisms that produce cellulase enzymes and enable them to digest cellulose. These animals can break down plant material and extract nutrients from it that would otherwise be unavailable.
In humans, cellulose passes through the digestive system largely undigested. However, some of the cellulose may be fermented by bacteria in the large intestine, producing short-chain fatty acids that can be absorbed and used as an energy source.
Therefore, while cellulose is not hydrolyzed by most animals, certain animals have adapted to digest cellulose through symbiotic relationships with microorganisms.