Horses are hindgut fermenters, while sheep are foregut fermenters.
Obtaining and transporting nutrients is a vital function for all multicellular organisms and different species have evolved some interesting ways of gaining, storing and digesting their nutrients. Amongst herbivores, for example, almost all have cellulose digesting bacteria within their gut that live symbiotically, assisting with the break down of vegetation. Some are classified as “hindgut fermenters”, which have microbes and fermentation in their hindgut, the caecum and proximal colon. These animals are less effecient at digesting their food and can sometimes be observed practising coprophagy (eating faeces).
Other herbivores are “foregut fermenters”, or ruminants, which have pouches with microbes in the stomach. These microbes consume glucose from cellulose but produce fatty acids that the animal can use for energy. Microbes can also be digested further along the digestive tract as they are also a source of protein. Forgut fermentation, or rumination, is a slower digestive process, but has the advantage of providing more nutrients and wasting less energy. Foregut fermenters include:
- Kangaroos and Wallabies
Good information about different types of digestive systems from a UK Veterinary site, Comparative Digestion.