Preheat the oven to 350℉.

Using your hands or a large 2-tined fork, lightly combine the turkey, onion, bread crumbs, carrots, celery, ½ cup of the ketchup, the mustard, parsley, and egg in a large bowl. Form into 1 large or 2 small loaves.

Place in one or two loaf pans. Combine the remaining ketchup with the tomato juice and pour over the loaf or loaves. Bake until firm and the tomato topping has set, about 1 hour for the large pan, 45 minutes for the smaller ones. Alternatively, shape a free-form loaf and place in a large pan that allows room for sauce to coat and surround the meat during cooking. Unmold the loaf or loaves and serve.