I'm not sure I understand it - this is a supplement, not a pharmaceutical ... what I do understand is that many OTC supplements are ineffective because there's no compulsory regulation as to ingredients, quality or quantity. Buying generic glucosamine from a supermarket may not work as well as getting it in the form of something like Cosequin, which is what I use.
I do believe it's not so much good without chondroitin, and many nutritionists believe it's even better with other things added like Vitamin C, and/or manganese, and/or Vitamin E. Some add boron into the mix, but that's more for the bone than the cartilage I think.
Ditto.
Also, I don't know that I've seen a food with even half enough glucosimine and chondroitin. I have fed both Wellness and Canidae and neither even came close to having enough of either. I stick with the suppliment and feed the food I think does best for the boys.
Exactly what I would do.