
At four weeks it should still be pretty mushy like thick porridge, you gradually increase the amount of kibble being added to the mix.
At four weeks I often give them one meal a day of different traditional foods, like minced meat, minced tripe, scrambled egg, chicken pieces etc.
With my medium breed the pups get up to 1/4 pint of Nutrolac, and after this I stop increasing the Milk, and by six weeks I give it as a drink after they have eaten their softened kibble, gradually moving to feeding the kibble just wetted with cold water (to stop the fun game of scattering dry kibble everywhere).
By the time they leave they get some of their food dry so they can be fed dry in their new homes (saves a lot of waste when working out volumes to feed).