When Do You Start Feeding Puppies Mush. Giant breed dogs are up and walking at 3 weeks old and can be started on food. At three weeks old, the pups are wormed with a mild wormer (they were also wormed at two weeks).

This process of transition lasts 7 to 8 weeks. Medium breeds can start food at 3.5 to 4.5 weeks of age. This process of transition lasts 7 to 8 weeks.