For a baby that young, I would think that duck soup might be too harsh on
her little system.  You might want to consider Esbilac (in pet stores).
Buy the canned and start off about 2 parts water, 1 part Esbilac, then move
up to half and half.  Mix the whole can and freeze into ice cubes.  It's
only good for about 48 hours after opening otherwise.  They do advertise
that their product is for ferrets (along with other animals).  As far as
the amount is concerned, let her eat until she is full.  If she is truly
that young, I would feed every 3-4 hours.  I would consider using a syringe
with a catac nipple instead of a bottle.  She might chew on the nipple on
the bottle and ingest pieces of it.  The catac nipples are much sturdier.
They can sometimes be found at pet stores in a package called Mothering
Kit.  Jeffers definitely carries them.  Just trash the syringe in the
package and use one from your vet or pharmacy.  When feeding from a bottle
or syringe, be careful she doesn't aspirate (milk coming out her nose).  If
she does aspirate, turn her upside down and tap her back to help get the
milk from her lungs.  Wipe the milk from her nose as it comes out so she
won't snort it back in.
 
You also might try just softening kibble for her with warm water.  Or
possibly soften the kibble with warm Esbilac.  Just be sure to remove it
after an hour or two so the Esbilac won't spoil.
 
Please, experienced breeders, correct me if I'm wrong.
 
Katharine
[Posted in FML issue 2819]