
One of my litters (four pups) were doing so well on Mum they hardly wanted any food until they were 4 1/2 weeks old.
As long as they are taking something then you know once Mums milk starts drying up that they will be used to getting their nourishment from another source.
There is nothing quite as good as mothers milk.
Interestingly enough that litter started eating loads almost overnight and within a week Mum was only giving them top ups morning and night.
All my girls wills till feed their pups at least once a day until they leave for their new homes, or even to 12 weeks if one stays.