Montego Classic Puppy Large Breed. The journey from puppy to adulthood is a special and crucial time in a dog’s life. Feeding a puppy incorrectly could affect their health in a number of ways, including obesity and malnutrition. So, before deciding on a food for your new pup (as well as just how much to feed them), you must consider the weight they’ll be when fully grown. Breeds vary in both growth rates and mature weights. So when it’s time to eat, pups need a diet, rich in the essential ingredients required to grow happily into the dog they’ll eventually become.