lol, sorry didn't notice this thread!! I don't know what the "precise" recommended dosage is, but I've given it to Lex for a long time daily, I splash what is equivalent to about 1-2 tablespoons on once a day.
As for the benefits of ACV (Apple Cider Vinegar) here is just one site that lists some of the benefits: http://www.hundmeister.com/acvbenefit.htm I'm not saying it is right for every dog - kinda like raw feeding (which I do)......best to do your own research to find out if it might be beneficial for your dog and if you are "comfortable" with it.