My understanding is that chickens are bred either for eggs or for meat. Egg farmers cull males as soon as they can (which depends on an interesting technical problem called sexing). Hens that can't lay anymore are called "spent hens", and the meat is not generally liked by Americans at least, so it's probably not what you're buying at the grocery store.

Poultry farmers raise both sexes and slaughter as soon as the bird is large enough.