I have a great vet who explained it to me like this:
 
1/4 Cup of Totally Ferret daily is enough to sustain a ferret.  This is
160 calories.  Now to add more power to the punch 1 tablespoon of Heavy
Cream is 50 calories, so a tablespoon or two added to duck soup made of
the Totally Ferret adds sufficient "extra" calories and fat to make up fo
the duck soup that ends up on the walls.
 
Using this formula I am feeding my guy about 90 cc's of duck soup daily
which provides more than enough calories and using a 12cc syringe it
takes minimal effort and with the cream added, he loves it.
 
Bear in mind that the cream may cause diarrhea as the ferret's body
adjusts.
[Posted in FML issue 3820]