Dogs need calcium! In the wild, they got their calcium from the blood and bones of their prey. Since our pets don't go out and hunt, we must provide them with the extra calcium needed. The best way to provide extra calcium for your dog with their homemade dog food is..... egg shells.
Rinse off the egg shells and let them air dry. Then place them in your oven at 275 for around 10 - 15 minutes (this makes it easier to crush the shells). Next you need to crush the shells into a fine powder form. The biggest thing is to make sure there are no sharp edges to the shells that could hurt your dog's insides. I went out and bought a marble mortar and pestle for around $15 to crush the shells. I then pass the powder through a small sifter to make sure I got it all.
You can also buy crushed egg shells online.
I use a ratio of 1/4 teaspoon of finely crushed egg shell to 1/4 lb of meat.
Learn more about vitamins, minerals, and supplements that are beneficial to your dog from Dog Food Secrets