1 st on the list, is to break up the carbohydrate many times. If you see, for example, Ground Rice, Rice Gluten Meal, Rice Flour or Rice Bran, the dog food manufacturers have broken up in this case, the rice, so that each ingredient, separately, weighs less than the protein. The other consideration is that the Gluten, Flour and Bran are low grade fillers, costing the dog food company much less than a whole product. I am not saying that there aren't any good dog foods on the market. Thanks to ongoing research into canine nutrition and the consumer becoming educated and aware, there are a few that are excellent for all stages of your dogs growth and overall welfare.
Lets talk about what is important in solid canine nutrition.
It is important to note, that, unlike people who vary their diets each day, dogs get basically the same entree twice a day, often for life. This makes it vital that we do not feed a food with chemical preservatives, harsh fillers, etc. It also makes it important that they get a truly balanced diet in all aspects. Giving your dog a food with one carbohydrate, even a nutritionally sound carbohydrates, is not as beneficial as balanced carbohydrates. Dogs are much the same.