I've used NutroMax for years. I use the stuff for the Overweight and Less Active dogs because it has the glucosamine in it. My 12 year old has some bone tumors that I don't believe are related to food, and my 15 year old is as healthy as a horse. I even feed it to my 2 and 3.5 year olds.
http://www.nutroproducts.com/maxdogprod.shtml