Suppliments
First off, supplements are not required for your dog to have a complete diet. These items are purely to provide additional fat, vitamins, minerals and nutrients. If you are feeding a complete diet (meat, bone and organ) you are more than likely fine and can give any of the items below as you wish, and in small doses.
Greek Yogurt- yogurt made in the style without gelatin
Alfalfa- powdered or tablet
Kelp- ground
Digestive Enzymes- powdered
Apple Cider Vinegar- liquid
Brewer's or Digestive Yeast- powdered
Eggs- with some of the shell
Vitamin C- liquid, powder, or chewable
Fish Oil- liquid or capsules
Flax Seed Oil- liquid or capsules
Cod Liver Oil- liquid or capsules