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]