Bar, A., Institute of Animal Science, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. Telephone: 08 470585
Fax: 08 475075
Vax, E., Institute of Animal Science, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. Telephone: 08 470585
Striem, S., Institute of Animal Science, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. Telephone: 08 470585

1. 1. Eggshell density (mg/cm2) and eggshell gland calbindin decreased in the aged hens. 2. 2. Aged hens which laid eggs with a low shell weight and shell density had significantly lower intestinal and eggshell gland calbindin as compared with those which laid eggs with a high shell weight and shell density. 3. 3. Significant correlations were found in aged hens between duodenal or eggshell calbindin and shell weight or shell density. 4. 4. The results suggest that: (a) aged hens forming light shells absorbed calcium with a lower efficiency than those forming heavy shells or than young hens; (b) the decline in shell density in the aged hens is caused by a physiological calcium deficiency or by a defect in the hens' ability to alter calbindin synthesis in response to calcium needs; (c) in the aged hens, the deposition of calcium into the eggshell is dependent on, or at least associated with, eggshell gland calbinclin. © 1992.