I have no idea. But animal feed in the UK used to be poorly regulated until the BSE scandal. Where it transpired that cattle offal was being fed back to cattle. I couldn't quite get why a ruminent herbivore was being fed meat in the first place. But it seems they were being fed loads of crap. I remember reading that even cement dust was being used to give them more weight. There was a recent TV program that was trying to push for waste foods like canteen waste to be fed to pigs - but the regulation was so tight it wasn't possible. Clean regulated insect feeds could help there (maybe..)