If a food without preservatives is being used (or if one with a
preservative which has a shorter time frame is being used) then people need
to be extra careful about food storage time both at stores and home,
please.  (We have and have had food with and without.) The fungi which can
start can have incredibly serious health consequences.  (One interesting
piece of history is about a walled city which wound up with it's gates
locked and the city turned into a refuge for the insane inhabitants after
fungus contaminated bread flour was used.  Think that problem was Ergot if
memory serves, but not sure.)  BTW, some components of toxins produced by
some of the fungi as well as those produced by some bacteria which can set
in are demonstrated to have carcinogenic properties.  The simple fact is
that when tackling risk factors there is NO such thing as being completely
safe, just in looking at the rates and making your own personal choices,
and that's true for all.  So, if you avoid preservatives just be extra
careful about time-frames and storage conditions of your ferret food, okay?
[Posted in FML issue 2613]