Our blackberry bushes had bark that peeled off pretty easily, so I am not sure how much fun it would be since you would probably lose most of the bark when you scrub it.
My dexter LOVES Blackberry sticks. We have them in our backyard so I know they are not sprayed. I wash them, dethorn them and boil and bake just like his apple wood.
I believe he eats the whole thing, since I dont seem to see bits in his cage. unlike the apple sticks that he just eats the bark from.
Ohhh how nice I have some huge untreated wild blackberry bushes on my property....I know they have never been sprayed since they grew out of a pile of dirt we moved 12 years ago!!!! I will have to try and see if chin likes this !