Seriously it's in the body of text in the post. Leftovers of the chickens that cannt be used for humans dogs and cats get used for the fish.

This is like people arguing against leather at this point when millions of animals are being slaughtered and their hides are being thrown into landfills because demand is so low. If they are already slaughtering the animals, use the parts. As demand for cows/chickens comes down find alternatives, but throwing away parts of a slaughtered animal is worse to me.