The small intestine is longer in herbivore than in carnivore because herbivores eat only grass which is full of cellulose and the digestion of cellulose takes a long time. Bile is a digestive juice secreted by the liver and stored in the gall bladder. The function of bile is to assist fat digestion and absorption in the gut. The length of small intestine differs in various animals depending on the food that they eat. Herbivores need a longer small intestine to allow cellulose to be digested as taken from green plants.