In nutritional studies (albeit on humans, but the process is so ancient that
it should be similar in ferrets in this case) fats SLOW digestion.  (Also,
note that Fox advises against polyunsaturates, though I have never read
anything bad about monosaturates.  We stick with the standard hairball
remedies here; they work and at times one just doesn't want to risk anything
less.  We don't give them or any laxatives as a routine practise, though,
preferring a varied diet and lots of exercise (which does help move things
through faster) for that.
[Posted in FML issue 2224]