
I would only use a milk formulated specifically for puppies. My own favourites are Nutrolac (sold by Animal Health) and made out of Goats Milk, and Litterlac (made of the usual Cows Milk) and sold through Champion foods.
Mine get milk right up to 8 weeks, and neither of those makes them loose. Have used Skinners Puppy Milk, but found they got a bit loose by 6 weeks. Lactol I found tended to Mix lumpy and is ver dear.