undernourished baby gerbil

Question
My female Mongolian gerbil just gave birth to 4 baby gerbils on March 30,2011 in a habitrail cage(this is her second litter). She is on her on her own in the cage except for her babies, but today(May 4th)i noticed that one baby is half the size of the others and VERY undernourished.I think the reason for the undernourishment is that since the other pups are so much bigger than her,they don't let her nurse,so she doesn't get enough milk. To  make her stronger i fed her 2 percent lactose free milk with an eye dropper.THe mom doesn't mind me taking her out to feed her,and when i put the baby back in the cage the mom takes the baby back into the nest with the other pups.Is there anything i can add to the milk help the baby pup become stronger and healthier?How often should i feed her? What exactly should i feed her?

Answer
Dear Jo,
thank you for your question.
Here is a good guide to raising orphaned rodents:
http://www.rmca.org/Articles/orphans.htm
Gerbils nurse about as long as rats and mice do, so you can use the information given on the website without changing anything.
I hope I was of some help to you
Jennifer