the thing about killing them first is not because they are hard to digest, it is because their jaws are strong enough to where they can actually chew their way out of the reptile/fish/ whatever they are fed to, by eating through the animal if they are not dead. At the store we always pinch their head off first, as a way to be sure, since there has been a few cases of them chewing through bearded dragons and leopard geckos stomaches. Crazy but it can happen so why take a chance.