We only use certified eggshell calcium in all of our products. Eggshell calcium is calcium carbonate, is high in elemental calcium, and has the same high bio-availability as calcium phosphate, found in bone.
Here are a couple of reasons why we made the choice to use organic eggshell calcium instead of ground-in bone:
#1) Many people and veterinarians have serious concerns about feeding raw ground bones. Ground bone is challenging for a cat's digestive system. We agree that this is good, but cats with sluggish digestive systems might have problems digesting bone shards. You are a better judge as to the value of bones in your cat's diet. That is why we recommend feeding bones in the natural condition a cat might find it - whole and chewable! You are at the mercy of the manufacturers on the size of bone shards in their grind. In a typical 'kill' for your backyard carnivore, he or she would most likely consume far less bone than is in a typical serving of food with bone ground in.
#2) It is difficult to guarantee the ratio of bone to meat unless every bone ground is exactly the same size. We have chosen to use organic eggshell calcium so that we can closely regulate the calcium and phosphorus content in our diets, which is so important for cats.
#3) Many cats suffer from constipation when consuming raw, ground bone on a regular basis. In order to maintain a proper calcium:phosphorus ratio, diets with ground bone can contain upwards of 10% bone, which is troublesome for many cats.