COWS can eat grass, so why can't humans?

COWS can eat grass, so why can't humans?

Plant cells contain something called cellulose that is very similar to the carbohydrate molecules in the food we eat.

But one bond in cellulose is different and we are unable to break it to get the energy out of the cellulose the way we can with other molecules.

We could eat grass but our bodies would not be able to digest it to get the energy we need.

Cows have a special bacteria living in their stomachs that make it possible for them to eat grass. - faqkids.com; answerbag.com