I think cream is good too, but I wouldn't worry about your girl being small. My Daffy is 1.4 lbs. She's 7 yrs old this week and her weight has been like this since I got her when she was 1 1/2 yrs old. As long as she's eating well and not acting sick, I wouldn't worry about it. Now when Daffy got insulinoma, she did go down to 1.2, but now she's back to 1.4. The other ferrets I've had over the years usually, but not always, gained weight over winter. But when summer came they lost it. My boys all gained about 1/2 lb during winter but lost it during summer. Out of the 6 girls I've had, only one weighed 2lbs, the others were 1.5 or smaller. Holly, the 2 pounder, was just a bigger ferret all around.
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Kat
Ferret mom to Jasmine and Daffy
A Cheesehead from Wisconsin