I've been to a factory that supplies McDonald's. they take a huge slab if beef, grind it, shape it, add a bit of salt and pepper and freeze it. That's it. It's even tested for fat content. Too little or too much and the whole batch is held back. Google it. There's loads of horror stories from 'friends of friends'/ insane animal rights activists. None are true. The USA/UK have strict food laws. Do you seriously think that some weird animal would get into McDonald's food chain unless by a freak accident?