Have you reviewed the studies on the frequent failure of glucosamine/chondroitin to do anything to help arthritis, at least in the common form sold by most manufacturers? We've discussed that research here many times, so I won't rehash it -- just know that the research probably doesn't support the effort you're putting into finding these supplements.
Google the GAIT study on glucosamine, and you'll find some good, long-term research -- there wasn't much in there to be excited about for glucosamine users. It was mostly a dud. The European study that saw some benefit that you may see touted by some manufacturers used a different form than the common over the counter form available to you. Similarly, a manufacturer-funded study by the maker of Dasuquin found a benefit in their patented form -- but it's a different low-molecular form than the one sold in most supplements.
Instead, with such a young dog, I would "supplement" with whole food sources -- like beef trachea, which contains them in a form the dog's body will recognize as "food." The dried trachea tubes are excellent chews.
If he has hip dysplasia but is not yet symptomatic, I would try to find out if Adequan is available in Europe. It's benefits are real, but expensive: it delays the onset of arthritis by keeping joints lubricated and preventing the degeneration of cartilage. It's an injection, prescribed by veterinarians -- it was developed for horses but is now widely used in dogs in the U.S.
Last edited by Magwart; 11-24-2018 at 11:41 AM.