Figure 1. Range of variation in the gross structure of the mammalian digestive tract. Most species have a simple stomach, but the stomach of some herbivores, such as the sheep, is enlarged and multicompartmental. The hindgut of most carnivores, such as the mole and dog is short and may or may not include a caecum. Omnivores tend to have a longer hindgut, which may be haustrated partially as in the rabbit or throughout its length, as in the domestic pig. The hindgut of most herbivores that lack a forestomach includes either a large caecum such as that of the rabbit or a large colon, as seen in the horse. Dog, rabbit, pig, pony and sheep, from Stevens (1977) with permission of the Cornell University Press; mole from Stevens and Hume (1995) with permission of the Cambridge University Press.

Figure 2. Bacterial fermentation of carbohydrates (a) and metabolism of nitrogenous compounds (b) in the hindgut of mammals. From Stevens and Hume (1995) with permission of the Cambridge University Press.