Foie gras was "discovered" by the Egyptians a few thousand years ago when they killed the geese keep around the grain silos to reduce the feed available to the rats. My ducks I raise each year overeat and become a bit restless when the warm mash is put out.
Let me think…animals that overeat to the point they ruin their health…go to any fast food place, on any day at almost any time…humans do it and yet we expect a bird w/ a brain the size of a walnut to be smarter?
The foie gras thing is totally political. PETA producers some really nasty (actually I took their pictures and modified them to a humane method five or so years ago…they never returned my emails thanking them for the education) but why would you put stress on an animal you want to produce a product. I am sitting at my desk watching thirty or so hens and ONE rooster (I’m coming back in my next Hindu life as him) eat fresh sprouts and cavort. Bad thing is he eats the same feed as the hens and the oyster shells in it are poison to him.
Battery hens are a totally different subject. Young hens can be subjected to the most horrible conditions (as they are daily) and still produce an egg every 28 hours. One year later they are in a pot pie or chicken noodle soup.