I give one once a week and crack it into my dog's food. If you have a large breed you could probably give two a week. I've heard a lot of dogs will instictively puncture the shell and suck out the egg....mine is a little stupid sometimes and he pounced on it and crushed it, then licked the egg off the floor. If your dog isn't into the shell, I wouldn't worry about it....as long as he eats a good-quality food he probably gets plenty of calcium. Or you can just grind it up like Sabine suggested.
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Chase (Friendly Resident Wigglebum) - Border Collie/Lab/Shepherd X
Kailey (Misunderstood Gentle Beauty) - GSD & foster failure #1
Rupert (Gold-Medal Winner of the 3 a.m. Kitty Destruction Olympics
)
Heidi - RIP my sweet baby girl