Canned food tends to hold a lot of water content in it ,banks may be getting enough in the canned food,we tend to forget that they are not like us popping the kettle on for a brew each hour,the canned food will be much like raw ,the dogs get all the fluid they need from it,if he's not dehydrated then he's getting enough fluid,try making some liver broth,simmer a small piece of liver until all the colour has come out of the liver,take the liver out and let the fluid cool,he may drink it and it's very good source of nutrients ,,also try taking his water bowl up and dont put it back down when you feed him,put it down after a few hours but in a different place,karen