GSD anything with alot of acidity will do that. I know that in some keeps TOMATO paste is used. Not sauce but concentrated paste to do the same thing. I havent ever heard of CIDER but I would think it would work
Thanks Oldfort. I've been giving him about a tablespoon twice a day. That sound good? It's the expensive stuff from the health food store to boot. Poor dog, I hate the smell and taste of vinegar but he don't seem to mind.