Posts tagged ‘cellulose’

The fibre in foods is made of a substance called cellulose. None of the digestive enzymes produced in the human gut can digest cellulose. This is why fibrous foods pass through the gut undigested. However, some animals, such as cattle and rabbits, feed on foods which contain a lot of cellulose. For example, grass contains a lot of cellulose. The digestive enzymes produced by cattle and rabbits cannot digest cellulose. These animals rely on the help of millions of microbes (bacteria and protozoa) which live in their gut. These microbes make an enzyme which digests cellulose. The soluble products of this digestion are released into the gut of the animal. The microbes feed on some of them. The rest of the soluble products of cellulose digestion pass through the gut wall of the cow or rabbit and into its blood.

The cow and rabbit both benefit from the microbes in their gut. Without these microbes, they would be unable to digest most of their food. The microbes also benefit. They have a safe warm home in the animal’s gut. When two different organisms live together so that both of them benefit, we call this symbiosis.

The cow is an interesting and important example of an animal which relies on microbes to help with cellulose digestion. The cow has a stomach made of four parts. The microbes live in the first chamber, which is called the rumen. All types of cattle are called ruminants because they have a rumen. Other examples of ruminants are goats, deer, antelopes, giraffes and sheep. Rabbits are not ruminants. They have a different way of making use of microbes for cellulose digestion, but that is another story.

Cows feed on grass. Grass contains a large amount of cellulose. Cows themselves cannot produce an enzyme which will digest cellulose. However, cellulose digestion takes place in the cow’s gut.