The rabbit is able to utilize forage because

The rabbit is able to utilize forage because it has an enlarged caecum that digests fibre. Unlike humans, rabbits are herbivores and feed on plant material that is difficult to digest. Their digestive system has a specialized structure that allows them to break down the cellulose and extract nutrients from it. The caecum is a large pouch located between the small and large intestine and is filled with bacteria and other microorganisms that break down fibre and other indigestible materials. This process produces volatile fatty acids and other byproducts that are absorbed and used as a source of energy by the rabbit. Thus, the rabbit is able to obtain nutrition from the forage it consumes.