Re-evaluation of calcium and phosphorus requirements in aged laying hens

1. A series of 5 trials was conducted with 401- to 650-d-old Lohmann, Yafa (local breed with brown eggshells) and Yarkon (local breed with white eggshells) hens fed for 56 to 84 d with diets containing 25 to 50 g/kg calcium (Ca) and 4·5 to 7·6 g/kg phosphorus (P).

2. Increasing dietary Ca from 24-25 to 36-40 g/kg improved egg production, shell weight (SW) and shell thickness (ST), and decreased mortality.

3. Increasing dietary Ca to 48 to 50 g/kg did not affect egg production but increased SW and/or ST. In one out of the 4 trials, this effect was not significant, most likely because of the high shell quality of the eggs from the Yafa hens used for this trial.

4. Dietary P content of 4·5 g/kg (1·0 g/kg added inorganic P) appears to be sufficient for maintaining egg production and shell quality in aged laying hen given 36 to 40 g/kg Ca.

5. Increasing dietary Ca above 40 g/kg may require a higher dietary P content.