Yes thats true, some animals, mammals to be exact, can digest cellulose.
Humans cannot digest cellulose as we have no cellulose digesting enzymes in the intestines.
Animals like rabbit (ruminants) can digest cellulose. They have certain bacteria anchored to their intestines to carry out cellulose digestion.
And besides, ruminants, after eliminating their faecal matter, re-ingest it .....yes, they do it! Actually, this ensures thorough digestion of cellulose, which is non-living matter of the plant cell wall.