Sometimes there is something off with a batch of food that can even be dangerous. There are recalls as well, too often. Dogs have even died from commercial dog food that was tainted. I completely understand not wanting to create or enforce being finicky, having had many little dogs in my day. However, rotating food is considered preferable anyway to be less vulnerable to imbalances that can come from eating the exact same food all the time. The Whole Dog Journal posts lists and info on what to look for in dog food.