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In laying hens, calcium (Ca) is of great importance in the eggshell, which requires for synthesis the deposition of about 2.2 g of Ca in the form of Ca carbonate (CaCO3). As egg production will be repeated daily over a long period (50 to 80 weeks), the hen finally exports huge amounts of body Ca for this purpose. Moreover, as the eggshell synthesis occurs mainly during the dark period, when the digestive tract is empty, an additional Ca reserve is mobilized from its bone with a very rapid bone turnover representing a huge challenge to Ca homeostasis and its underlying regulations. The available knowledge on the subject is presented and discussed in the following manuscript, with reference to applied perspectives for the egg producing sector.
- 1 Introduction
- 2 Eggshell calcifcation and calcium (Ca) requirements in the laying hen
- 3 Underlying and regulatory mechanisms in the laying hen
- 4 Bone as a major Ca reservoir for the laying hen
- 5 Clearance by the kidney
- 6 Regulatory factors
- 7 FGF23: a new research topic in poultry calcium and phosphorus metabolism
- 8 Case study: alteration of Ca homeostasis by diet or age in laying hens
- 9 Comparing optimal and suboptimal diets affecting Ca homeostasis in laying hens
- 10 Comparing hens at the peak versus the end of lay
- 11 Conclusion and future trends
- 12 Where to look for further information
- 13 References