You should give Omnivore’s Dilemma a read, where Michael Pollan discovers that even “grass fed” and “organic” are terms that policy makers have basically all but handed over to the industrial food industry. Example: “grass fed” is just a stipulation that animals have the availability to graze on grass, and they may still be fed a cheap corn meal. In fact, chickens are so conditioned from birth to stay in the hen house that they often don’t step out once in their lifetime to graze the grass that is made available to them — and they can legally still be called grass fed.
I agree, that the best thing we can do is eat local food, but be wary of the stories that brands (e.g. those at Whole Foods) built around a collective desire for health and wellness tell you on their packaging — it’s unlikely to be whole story.