Now think what a cow eats. Grass. Just grass. Delicious grass. Cows aren’t quite as advanced as (most) humans, but they still need a whole smorgasbord of nutrients to stay healthy. They need to get them all from grass.
To squeeze every last drop of goodness from their boring diet, cows need a pretty intensive digestive system:
After a cow swallows its food, the grass mush makes its way to a pair of pouches called the rumen and the reticulum. These chambers are big – up to the size of a 55-gallon trashcan – and are full of millions of bacteria. These bacteria are key to how cows digest what we can’t: they are able to break down cellulose (what we call ‘fibre’) – a tough plant molecule that mammals can’t digest on their own.
The bacteria and the cow help each other survive in a symbiotic relationship- in return for their digestive help the bacteria get the privilege of living inside a cow’s stomach. Lucky them.
To make sure absolutely everything is broken down, the cow regurgitates the partially-digested food and gives it another chew. This process, ‘chewing the cud’ can go on for several days.
After re-swallowing one final time, the mush then passes through an absorption chamber called the omasum before ending up in the abomasum. This final chamber is similar to the human stomach. Here the food is digested one last time before what’s left is sent on its way to the exit pipe.
So to say a cow has more than one stomach is not strictly true – it actually has one stomach with four compartments, amounting to a super-efficient grass-digesting, cellulose-fermenting machine.
And the next time you complain about indigestion, just be grateful you don’t have to vomit up and chew on semi-digested grass mush every day.
Image credit: Jan Glas on flickr