COMBINE first 9 ingredients in a large bowl; stir well. Form meat mixture into a loaf and place in 9x5 inch loaf pan.
COMBINE 1/2 cup ketchup, brown sugar, 1 Tablespoon horseradish, and mustard in a small bowl, stirring well. Spoon half of ketchup mixture over top of meat loaf. Bake, uncovered, at 375 degrees, for 1 hour and 15 minutes. Spoon remaining ketchup mixture over meat loaf, and bake 10 more minutes. Remove to a serving platter.