At fast I thought it was a obnoxious vice when I saw rabbits eating their own faeces. But later learn its part of their digestive process for non-ruminants do not do rumination.
In rabbits and rodents there is very little absorption of the products of fermentation after microorganisms break down cellulose to glucose in caecum-mammals do not secrete cellulase, the enzyme responsible for digestion of cellulose. They however, solve the problem by ingesting their faeces. These pass through the stomach and small intestine where their contents are subjected to further digestion and absorption.
This is a very important source of nutrients for such animals. Rabbits and rodents egest two types of faeces. One type consists of soft, moist and nutrient-rich faeces which are eaten immediately. The second type consists of hard, dry pellets which have passed through the digestive system twice and are discarded.