I have a 12 yr. old great dane. She has always been thin. The vet has always said that she is healthy and that is just her. She was the runt of the litter. I had blood work done on her recently and everything is fine. My question is should I now try to give her anything to "fatten" her up. She shows her ribs and people look at her as if she is malnourished. She moves slower, dribbles pee, yet will jump around like a wild pony when she hears my daughters car. I mix a can of wet food with her dry to get her to eat more, but she is still thin.Any thoughts?