For those seriously interested in learning everything about dog food without pulling your hair out...there is a site, it costs $17 per year to join...but they keep up on all of the dog food/treat issues and they ask the companies all the questions, they analyze all ingredients and rate the dog foods accordingly...they highlight harmful additives in red...pretty good resource. I joined. It is called Truth About Pet Food and it is part of the Petsumer.com page.
http://www.petsumerreport.com/index.html there is one section that you have to join to access, and that is the petsumer report...which, in my opinion, is worth every penny!