FWIW, my daughter works for a pet food company as a nutritionist / formulator. I asked her about this, and her take is that there is something going on, we do not really understand what and how, but for now, better safe than sorry.
After she got out of grad school, she took "her" dog to live with her, and she continues to feed her Costco's Kirkland Lamb and Rice, although she is now switching over to the Senior formula (the bitch is now 11 1/2, but still acts like a puppy).
Just as a general observation, since I deal with animal feed formulations on a farm scale, there are currently large problems with several of the animal meal categories, particularly pork, chicken and some fish meals. In general, the quality of meals has gone down both in nutritional quality and in the occurrences of things like oxidation and oxidation related chemicals (think rancidity). Same thing for animal based oils (chicken fat and fish oil, in particular). Unless a manufacturer is very diligent and is proactive about ingredient quality, it's a crap shoot out there.
