Limestone Products
What do eggshells and limestone have in common?
A hen builds one every day, out of limestone.
Dr. Lime Explains
An eggshell is limestone. Almost exactly the same mineral, and about 95% of the shell.
A hen builds one shell every day. To do it, she needs about 4 grams of calcium.
She builds most of the shell at night, long after she has finished eating. So the calcium has to stay in her body and release slowly.
This is why the size of the limestone particles matters. Fine powder passes through her too fast. Coarser grit stays longer, and releases calcium through the night.
Worth knowing
A hen lays around 300 eggs a year. That is about 1.5 kilograms of shell, far more than her own skeleton weighs. If her feed does not give her enough calcium, she does not stop laying. She takes the calcium from her own bones instead.
Source: National Research Council, Nutrient Requirements of Poultry.
