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By now, you know that not all meat is created equal. That familiar fable about Old MacDonald and his happy barnyard menagerie is a far cry from the cruel reality of factory farms, where cows, pigs, and chickens are crammed together in giant warehouses, fattened on grain, and pumped full of antibiotics, then rolled out to the slaughterhouse to become the next Big Mac or box of McNuggets.

In regulatory lingo, these meat factories are called “concentrated animal feeding operations,” or CAFOs. (Pronounced “cay-fo.”) Here’s everything you ever wanted to know about them — and a few things you’d probably rather not know.