For many years I gave large raw marrow bones to my dogs as being good for their teeth and gums, until one day my Swedish Valhund managed to break off a piece small enough to get stuck in her throat. This necessitated an operation and vet fees.
I always clean up poop from my dogs, every time they go out and do one. Can't say I've ever notice white bits in it, apart from once a foster galga arrived from Spain who supposedly had been wormed...but definitely hadn't! However, I thought you might be interested to read this article.