The Effect of Diet on Animals' Digestive Systems

 Herbivores, animals like horses and cattle that eat only plant material, depend on help from microorganisms somewhere in their digestive tube to break down cellulose (microbial fermentation). In order for this to happen, there has to be some sort of enlarged fermentation vat in the system. In cattle this is the rumen, and in horses it is their enlarged large intestine.

Carnivores, like dogs and cats, eat meat which is easier to break down than cellulose. They depend mainly on enzymes to break down their foods and, therefore, don't need any enlarged segments in their digestive tubes.

Omnivores, like pigs, eat both plant and animal material. They depend mainly on enzymes for digestion, but some microbial fermentation takes place in their enlarged large intestine.