To help ease your ferret back to the regular kibble I would suggest
chopping up the kibble and adding to the canned food.  Start with it
finely ground and mix it in, then make the chunks slowly bigger.
Hopefully he'll get used to it slowly all the way up to full size chunks
with just a little canned food.  The small ground pieces will also be
hard for him to pick out.
 
Good luck
Risa
[Posted in FML issue 4941]