There are big differences in the developmental needs of small and medium puppies in comparison to large breeds. In general, large breed puppies take about 3-4 years to mature, while small breed puppies take only from 6 months to 1 year!
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Small breed puppies have a very fast metabolism and thus requires more “fuel” and protein for the body to grow. Similarly, the fat and calorie content of small breed puppy food needs to be high. Think of a dog’s body as a house. To build the house we need a lot of bricks. Proteins are the bricks that the body uses to grow. To construct this house workers are needed to put up the bricks. The fat and calories are the workmen. Because their fast metabolism will readily compensate for excess, it is important to err on the side of providing more protein ‘bricks’ and more ‘builder’ fat and calories so as not to deprive the small or medium breed puppy of these essential fuels.
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Large breed puppies have very different considerations. Take the Great Dane as an example. The Great Dane’s head is huge, the body is long, and the legs are really long. Growth for a dog with this much bone mass must be delicate and slow, so the bones and joints may properly grow layer by layer. Otherwise the legs will curve, or the toes point in or out, and other problems may crop up. Therefore, we must be careful about the number of protein ‘bricks’ we use and how fast we use them. And, ‘worker’ fat and calories must be moderated to reduce the possibility of excess weight burdening the growing bones. Moderation is the key to large puppy growth!
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The last major distinction between small and large breed puppy foods is the balance of calcium and phosphorous. These minerals play a major role in bone growth in both small and large breed puppies. Due to their fast rate of growth, the small breed puppy can use more calcium and phosphorous than the large breed puppy.