Or all that shit (literally) that goes into the chickens' mouths long before we eat it.
Same goes with cattle. They're fed decomposing parts of other cows and cow shit.
It must enhance the flavor of the meat, or just make it cheaper for the people selling it.
Hunting is the most humane way to eat an animal. Any largely processed meat probably comes from animals that had a pretty bad life, especially the last few hours.