I don't think peanut butter is harmful to ferrets, but I don't know. I've been giving my ferrets [Kraft] unsweetened, unsalted peanut butter for several years as a treat. They really like it. Their stools are a bit runny if they have too much, but other than that, they seem fine. I started giving the unsweetened, unsalted peanut butter to a ferret that had insulinoma, and then continued giving it as a treat to other ferrets. Inez [Posted in FML 6862]