Well, I hate to break it to you, but it looks like the Rachel Ray is worse than the Zignature food. If you check out both foods brands you mentioned on dogfoodadvisor.com (I know I mention this site a lot on here, I swear I'm not affiliated, haha) Zignature received 4 stars, whereas the Rachel Ray brand received 3, I'm assuming you're talking about the "Just 6" variety. Her other dry food received 2.5 stars. Here are the links:
Now, I didn't read much deeper than the ratings, you can check out their reviews and see if you agree/disagree, etc. Obviously at the end of the day, the choice is yours what to feed your dogs, some ingredients are controversial, but not necessarily proven to be bad. I personally switched my dog to the Acana Regionals, which won't be found at Wal-Mart either most likely, but they received a 5-star rating (link below) and they're around the 20 dollar price range as well. I have to purchase it from a local non-chain pet store near my house, but I'm happy to support a local business. You could also use the site to research different brands available at Wal-Mart, there might be some good options, I'm not sure. Good luck!
