I would suggest not worrying to much on the fillers (feathers etc)and focus on the fish meal/oil as the fats/lipids/protein source for BG, LMB , HSB , YP etc.. I like Purina products and trust Mark to give good info. AM also includes feathers just as most do but the key is top quality fish meal/oil. There is a fish food links thread in the archives to many producers to compare. Have read and digested (no pun intended) quite a few studies on fish food/nutrition.