my vet recommended dog food

Today my veterinarian recommended WholeMeals. On it’s face it sounds pretty good. They say it is formulated for your dog’s health and happiness.

So, I then read the ingredients label and find that the first two ingredients are Rice Meal and Chicken by product meal. With a notation that the chicken filler is a “natural” source of glucosomine and chondroitin. How is that possible? A by product being a natural source of anything. It says no filler but isnt a chicken by-product meal a form of filler?

And it ends of stating that it is NOT an essential nutrient by the AAFCO.