Ground eggshells is the perfect calcium and phosphorus ratio to ensure a compete and balanced diet for your dog. There are more requirements to ensure your pet is getting the required nutrients and vitamins, but this is a great start.
Rinse shells before cracking eggs, when possible.
Save used eggshells in fridge or freezer.
When enough are accumulated Bake shells @ 300 for 20 min.
Crush them w/ a rolling pin or put in a food processor.
Sprinkle on top of your pups food.