I didn’t think many people gave supplements to their dogs or cats, so I was amazed to discover recently that 75 percent of people with dogs purchase vitamins or mineral supplements for them, according to a survey done by the AKC (the American Kennel Club, which runs dog shows and a registry for dogs). The reason this surprises me is that the vast majority of people feed commercial food and highly processed foods that are already supplemented with a full balance of all the officially required vitamins a dog or cat needs. (As an aside, it seems to me that one of the reasons that pets can survive on the…