If you are interested in knowing what your puppy's nutritional needs are, based on scientific research and not information based on any brand of pet food, there are great educational materials....I have copies of many, many articles on dog food and nutrition and what you dog actually needs nutrition wise, at all stages of their life. I can not copy/paste those articles because they wont allow it.
You can learn what your dogs nutritional needs are, based on scientific research, produced by the National Research Council of the National Academies, who are advisers to the Nation on Science, Engineering, and Medicine. You can access their site by
http://dels.nes.edu/banr. Also check out
Home | National-Academies.org | Where the Nation Turns for Independent, Expert Advice
These sites give you unbiased information on exactly what your puppy/dog requires for proper nutrition. These people do not formulate or sell or recommend pet food, it is all scientific and evidenced based research. There is no recommendations for a specific brand, but you can get the percentages needed of protein, fats, carbs, etc, as well as minerals and vitamins. You can check the brand you select with what is scientifically researched and determined as necessary for proper nutrition for your dog.....what some people consider "crappy food" is crappy because it does not meet the owners requirement for their pet, what owners like and do not like, and it may in fact, not be crappy at all, based on food for your pet!
Do your own research, using scientific and medical research, not hear say or opinions that are not based on solid, verified research! Good luck with your quest for "The Perfect Food"!!! I would strongly suggest you take a can of that Purina puppy food, compare it to the "recommended daily requirements" as given on the site I gave you, and see if it meets those requirements, without the supplement the breeder is also giving. If it meets the daily requirements, I would NOT be changing a brand new puppy to a brand new food as soon as you get her home. It is unnecessary stress on that puppy, and you can easily create more issues than you think your are avoiding.