Have you tried getting a can of the A/D from your vet and mixing with a
little water and either syringe feeding or possibly letting them eat out
of bowl?  A/D is for both cats and dogs when they are ill and it has a
lot of good stuff in it.  Usually I have pretty good luck with giving to
my fuzzies a few times a day in addition to their regular dry ferret food.
 
Good Luck!
 
Missy and the Pietinkieville Gang from Ohio!
[Posted in FML issue 3839]