We never give cows milk to dogs .
Most dogs are lactose intolerant and develop diarrhea.
You can start weaning the pups at 3-4 weeks by soaking puppy food in warm water to soften it. I usually put the mixture in a blender and blend it to the consistency of a milk shake to start out. Make sure you keep mom away from the pups for a couple of hours to make sure the pups are hungry. Then I feed them using pie pans so they can get at the puppy food. Usually weaning takes 1-2 weeks.