Animal rights groups say dogs are kept in cages and have their blood drained every week in order to save the life of other pets. California-based animal welfare activist Robyn Black wasn’t ready to say goodbye to her beloved corgi, Sir Winston, when he suddenly came down with an autoimmune disease six years ago. She told her veterinarian to do whatever was needed to save the 5-year-old dog’s life. Black dropped off Winston at her Sacramento vet’s office on a Friday afternoon. By Sunday evening, the animal clinic was running…