Take a look at this web site:

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This place has been around for over 30+ years as a catalog and on-site source. Their stuff is pretty high quality.
Glucosamine and Chondroitin have been used for about 20 years on pets? Over 30+ years on larger animals...but...before giving this stuff? I would see my vet, IF I were you. Why? Because it can only help so much, and what the real problem mite be mite mean you are putting costly supplements into your pet to no real advantage in the long term.
First, find out w/your vet what you are dealing with. Then deal with your dear more knowlegeably and sensibly. Go from there and see what works?

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!!!!!!!!!!!! For now... let us know, please. - j