Self-selection of calcium during the rearing and early laying periods of White Leghorn pullets.

The ability of pullets to selectively consume calcium to meet the requirements of the rearing and early laying period was studied in White Leghorns. In the first of two experiments, 456 pullets were fed either an .89% calcium rearing diet (control) or a .35% calcium diet in combination with a separate source of 38% calcium chick-sized grit (calcium self-selection) from 35 to 126 days of age. Twenty-four pullets from each of these rearing treatments were selected for the second experiment at 112 days of age and were housed in individual laying cages. Rearing treatments were continued until 176 days of age with mash and grit consumption recorded daily for each pullet. From 177 to 225 days of age these pullets were fed a 3.50% calcium diet containing either ground limestone or oyster shell as a calcium source or a .35% calcium diet fed in combination with a separate source of oyster shell. Pullet calcium intake reflected the requirements for growth during the rearing period, calcium storage in the medullary bone 19 days prior to lay, and egg shell formation during the laying period; average calcium intake for these periods was 1.18, 2.08, and greater than 3.50%, respectively. Pullets also demonstrated the ability to compensate for rearing deficiencies by increased calcium consumption when fed oyster shell on an ad lib basis. Calcium consumption was found to be significantly higher on days when an oviposition occurred than when no eggs were laid. Mash consumption during the early laying period also reflected the reproductive status of the hen with the highest consumption on days when both oviposition and ovulation occurred, intermediate consumption when either oviposition or ovulation occurred, and lowest consumption when neither oviposition nor ovulation was detected.