I'm not going to go off on a rant about animal cruelty, but I definitely advise keeping an eye on Dog when there's weed about. I doubt anyone has done a study on what's the lethal dose or anything, or what causes permanent brain damage, but there's got to be a point at which getting your dog a bit stoned is different from letting them eat your whole stash, even by mistake.
So let's all keep anything more than a nug or 2 out of reach of our furry and VERY dumb best friends! BTW I give my dog all my stems. She likes gnawing on them.