Ruminants and birds

Do all animals digest food the way we do? Have you seen a cow chewing away even when it is not grazing?

Grass-eating animals like cows and buffaloes chew grass only partly and swallow it into the stomach, where it is partly digested. (Their stomach has four chambers.)

The partly digested food is then brought back up to the mouth to be chewed slowly all over again. This is called rumination (in Hindi, जुगाली), and animals that do it are called ruminants. A cow spends about 8 hours a day just chewing!

After that thorough second chewing, the food goes back down the alimentary canal to be digested further.

Birds do it differently again. They have no teeth. Instead they have a muscular chamber called the gizzard. Its walls squeeze and relax to grind the food, often helped by grit — small stones the bird has swallowed, which act like teeth inside.

So animals have different kinds of alimentary canals, each suited to the kind of food they eat and how they digest it.

Once food is digested, its nutrients travel round the body. Some build and repair the body. Others, like sugar, are broken down inside the body to release energy. That process, turning nutrients into usable energy, is called respiration.