ABSTRACT
Herbivores, animals that can utilize the fi brous portion of plants, are represented in 11 of the 20 mammalian orders, fi ve of which contain only herbivores (Stevens 1989). Fibrous portions such as cellulose and hemicellulose are not digested by enzymes secreted by mammals but are broken down by microbial fermentation involving both bacteria and protozoans. Fermentation of these polysaccharides occurs principally in a single segment of the digestive tract. In foregut fermenters such as ruminants, camels and kangaroos, fermentation takes place in a modifi ed portion of the stomach prior to the “gastric part of the stomach” and small intestine. In hindgut fermenters, fermentation takes place in the posterior part of the gut. In this group, the larger herbivores such as elephants and horses use the colon as the main fermentation chamber, while the smaller herbivores such as rodents mainly use the cecum (Hume 1989). The capybara is the largest cecum fermenter (Borges et al. 1996). Furthermore, foregut fermenters, principally ruminants, predominate in the 10 to 600 kg group size, while hindgut fermenters predominate among small and very large herbivores (Demment and van Soest 1985). Foregut fermenters are considered to be more effi cient utilizers of cell wall constituents than hindgut fermenters (van Soest 1982).
