Your dog certainly could be different, however a normal healthy dog can efficently process a species appropriate protein, meaning animal meat and not corn. There are different sources of proteins that are used in commercial dog foods that while they are a source of protein they do not digest as well because they are not species appropriate. The rX food your dog is on contains protein, however the sources are corn and by-products which are not sufficent sources of protein. The by-products are the least of the problem because if paired with whole meat wouldnt be terrible, its the abudance of corn and rices that are difficult to digest.
I would highly consider a commercial raw diet. A little different than what L M suggested, however the maker of the commercial raw food usually works with a holistic vet ( i know Darwins does) to make sure all the vitamins, minerals, antioxidants, etc are in the food at the proper levels, where as when you make the food yourself you need to be able to formulate those levels on your own which if you are new to it can be much more scary.
Despite recipes and all that, you still need to be careful when preparing your own homemade raw diet.
