I thought we had argued about this already.....
Here is some information from one of my favorire sites-
link located below
Dogs need a food product appropriate for their life stage
This is what pet food manufacturers want you to believe, but it is just a way to secure their customer base early on and increase sales. The more items in a particular line of food, the higher the visibility of their product on a store shelf - an of course the more likely people are to buy and stick with the brand through the whole life of the animal. Fact is that a food declared as suitable "for all lifestages" will feed a growing puppy just as well as a lactating bitch, an adult or a senior dog - just the amounts you have to feed will change. Puppy and senior food is often more expensive than the regular type of food of the same brand, yet does not differ much in nutritional value. Compare the guaranteed analysis and ingredient list.
Further, puppy food can cause large and giant breed puppies to grow at maximum rate, which is not healthy for them. A slower, more even growth results in far less risk of orthopedic problems and a healthier adult dog.
The Dog Food Project - Myths about Dog Nutrition
p.s This site is not biased towards any particular food.
oh- and having worked in a retail pet supply store for 6 years I can verify that yes indeed companies- such as Royal Canin will have 15 different SKU's so they have more shelf space. Not to say there is no difference in all the foods but in quite a few of them they are very similar but target different customers.....tricky thing the petfood industry....
-amanda