Changes in egg shell thickness and white and yolk weight and composition over a period of a year

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Abstract
A study has been made of all eggs laid over a year (March-March) by twelve birds.It was found that:1. Shell thickness, yolk weight and white weight all increased with time.2. For each individual bird a linear relationship existed between yolk weight and yolk calcium weight and between yolk weight and yolk phosphorus weight.3. High calcium diets significantly increased shell thickness at the beginning of the experiment and yolk calcium around the middle of the experiment. Dietary calcium levels had no other effects and dietary phosphorus levels no effects at all.4. The ‘curves’ relating shell thickness and time for each individual bird are discussed in relation to the relative merits of different birds as producers of thick shells.