Chicks
Requirementof Calcium is high because of poor feed intake, thus an immediate Calcium supplementation results in better bone formation.

Grower & Broiler
Third week onwards bird grow at a rate much faster & quite often body mass of the bird & the skeleton are disproportione, Calcium supplementation at this stage always helps in strengthening the bones, resulting in better growth.

Layer
Since 2-3 gm Calcium is required for the formation of egg shell, quite often it results in excretion of calcium from bones, this is advised to provide extra Calcium at this stage.