I want to know if you do only feed your dogs their dog food or do you add any vitamins and/or minerals such as Glucosamine or something else to their food when they are growing up to help reduce any joint problems?

Only my older dogs that need supplements (G/C/MSM) get it. I don't supplement them when they are young.

But I am not a big believer in vitamins and supplements for humans either. If you eat a good and balanced diet, you should be getting what you need from good nutrition. Same for dogs.