Pulled my beef roast out of the slow cooker and saw these weird white stringy things poking out of the meat. They look like little worms or parasites. Is the meat infested?

apart, while parasites would appear as distinct, firm, uniform structures. If your beef smells normal, was stored safely, and reached a safe internal temperature, those “worms” are almost certainly harmless collagen—nothing more than the science of slow cooking on your plate.