I'm having a hard time finding bone meal powder containing only calcium and phosphorus, with a calcium-to-phosphorus ratio close to the recommended ratios (click here for an earlier post explaining this important ratio). Until I buy some new bone meal powder I decided to make egg shell powder to supplement Gracie's meals.
Several books, including Dr. Pitcairn's, tell how to do this. Over the course of two or three days I saved some egg shells and washed and dried them. I then put them in a 300 degree F oven for 15 minutes, even though 10 minutes is the recommended oven time. I feel like the extra five minutes might help kill more bacteria but I'm not even sure that's what the oven time is for. One source said it's to help remove a type of wax that's sometimes put on commercially produced eggs.
After removing the eggshells from the oven I cooled them to room temperature and ground them in a coffee and spice mill. I ground them thoroughly, to avoid leaving any large or sharp pieces. I've added small amounts of this eggshell powder to some of Gracie's meals, for a calcium supplement.
According to Dr. Pitcairn's book, eggshells contain a 1,800 mg-to- 6 mg calcium-to-phosphorus ratio, so excessive use can supply way too much calcium in a dog's diet. Bone meal provides a better calcium-to-phosphorus ratio for a calcium supplement so I'll keep searching for a brand I like.
*** POST UPDATE: The ground egg shells were just a temporary calcium supplement. I'm now using KAL Bone Meal Powder. According to the label on this new bottle, 1 teaspoon (6g) contains: 1620 mg calcium (from Bone Meal), 540 mg phosphorus (from Bone Meal) and 18 mg magnesium (from Bone Meal). It's not an ideal calcium-to-phosphorus ratio but Gracie's meals contain enough phosphorus to balance it out.