Salt can be toxic to ferrets if fed as part of the regular diet. 8
of 30 ferrets fed with tuna preserved in brine died with days of
commencing this diet.

Biology and Diseases of the Ferret 2nd. ed. (Fox) page 169.

Tony (not a vet), Sugar and Suki.
In memory of Sally and Sue. 

[Posted in FML 6235]