To overcome this herbivores have developed a symbiotic relationship with a population of microflora that inhabit a specialised region of the gut for fermentation . the caecum or rumen of ruminants. The microflora population of the gut is able to breakdown cellulose and use the glucose for its own metabolic needs. As a waste product of this process, the microflora population releases volatile fatty acids (. acetate, butyrate & propionate) which the herbivore utilises for energy. The production of these fatty acids is known as fermentation (fermentation also produces heat which keeps the animal warm).