If it is a large breed puppy, yogurt is a stupid idea. Most puppy chows have close to the maximum amount of calcium to avoid joint damage. Adding yogurt, milk, or any other rich source of calcium can wreck their joints. Don't do it. Ignore any other advice from that source.
New puppies may take a little while to adjust, but soon should be eating all they need. Over fed puppies may not eat well either. The solution isn't bribing them to eat more than they need. Over weight is hard on any dog, but another way of creating joint problems in large breeds.