how important is glucosamine/chondroitan, how much is needed

[dosgris]

my dogs seem to be doing very well on a mix of black gold 26/18 and diamond ultra 30/20. five parts black gold to one part diamond. now why am i going through all the trouble to mix them???? because the diamond ultra has glucosamine/chondroiton, as well as flax seed oil, omega 6 and omega 3 fats and i am thinking that this is good for the dogs. now at a five to one mix i know that they aren't getting very much,, and my question is how much chondroiton and glucosamine do older dogs need for it to make a difference in their joints and all??? i have one large dog and one old dog and i think these two in particular need these type of supplements,,, however i am sure that it can't hurt even the young ones,,, as i am sure that a few hours of running through the briars after days of inactivity in the kennel must be tough on their legs and joints. does anyone know how much of these substances is needed to make a difference in a dog's life??