74 74 Once in production, the calcium needed for shell formation mainly comes from the diet and the medullary bone, latter provides between 30–40% of it. The quality of the shell will depend on the amount of calcium available in the digestive tract during the night and the form in which carbonate is provided. CRUCIAL TO MAINTAIN LONG PRODUCTION CYCLES ENSURES THE WELLBEING OF THE BIRDS The eggshell is an important source of calcium for the developing embryo. The mammillary layer, which is a major source of calcium, should be thick to provide sufficient calcium during incubation. THE EGGSHELL Makes up 9–10% of the egg's weight Composed of 95% calcium carbonate (40% of which is calcium) Shell calcium content ranges from 2.2–2.5% LOHMANN › MANAGEMENT GUIDE › NUTRITION › VITAMINS & MINERALS CALCIUM . . . during the preparation period will affect the strength and size of the bones and later will impact on shell quality, increasing the percentage of broken eggs, reducing production, and even potentially increasing bird mortality. . . . during the production period, along with continuous resorption, will progressively weaken the bones, increasing susceptibility to fractures. CALCIUM DEFICIENCY . . .
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