Purina is only a 2 star dog food out of 6 stars..here's a link to see the quality of the food you feed or are thinking of feeding...
Dog Food Ratings by Brand
Anything you can buy at a grocery store or walmart...etc..is usually only 2 stars...terribly low quality food...hardly any nutrition in it at all.
If you go to a Pet specialty shop you can usually find high quality dog foods..
My girls prefer Canadai...grain free....I've tried ALOT of premium foods!! they are very picky eaters..it's only a 5 star...but superior compared to what I used to feed a long time ago, which was pedigree.
Some stores offer free samples of premium foods to try.