I am a newbie groomer and have been looking at old posts. I thought I would add something here. Purina isn't a very good food if you look at the ingredients. Ol Roy is one of the worst food you can feed according to a vet I used to work for. We feed Natures Recipe for easy digestion as my dogs are prone to digestive problems. I don't like Science Diet. If you look at the ingredients it uses corn which isn't good. Anything with corn as a filler is bad. I don't recommend it unless a vet says use it for a certain condition such as a diet or whatever. Corn has no nutritional value at all. Wheat isn't good either. I don't know what Iams has in it, just look at the label or compare foods online at Petsmart.com. I hope this helps. My dogs really like Nature's Recipe. You can also go to the more expensive Natural Balance which is good. I don not know if Nature's Recipe has a senior food. It probably would be good to do a search at Petsmart.com and see what is available, do some research, before you go buy.