the theory is that in the wild a dog (a carnivor but oportunist) would never get "puppy food"..that the pups would just eat more..hence the all life stages "als" style foods. Thats one theory I read...Also in my opionion if you look at one of the often mentioned
Dog Food Analysis - Reviews of kibble (i think thats the right one..i have many stored)...you'll see that if you search say Canidae you'll get a couple versions of their food. Then search Nutro...the variations of food they have is huge...to me that says "we're more interested in reaching any and all markets for sales purposes. I'm interested in studying up on "raw diet" a bit. All my opionion- but ask my wife...I'm usually wrong. Ha!
-also I have heard complaints on here about the "expertiese" of the food analysis people- or lack there of.
-and I'm sorry for picking on nutro...it may be great for some...i just feel i had a bad experience with them.
-another note; you'll proably never get a diffinitive awnser...it will be a best judgement and then trial and error....good luck.