Relationship of Calcium to Reproductive Abnormalities in the Laying Hen (Gallus domesticus)

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Abstract
A reduction in weight of ovary, oviduct and body and a decrease in egg production and feed consumption were observed in hens fed a diet containing 0.05% calcium. Adenohypophyses of calcium-deficient hens had increased amounts of periodic acid-Schiff-positive material (secretory in nature) indicating that hormones were produced but not released. Luteinizing hormone and adenohypophysis extract increased soft-shell egg production of calcium-deficient hens approximately 200 to 300% compared to that of calcium-deficient hens injected with physiological saline. The injection of hypothalamus extracts into birds fed a diet containing 0.05% calcium increased soft-shell egg production approximately 300 to 400% and also significantly increased ovary and oviduct weight and significantly decreased bone ash. Hormonal injections had no significant influence on soft-shell egg production in birds fed a diet containing 3.00% calcium. The results of these studies suggest that the secretion or production of gonadotropic hormones was reduced with prolonged calcium deficiency resulting in adverse effects on the reproductive system of laying hens. The ability of hypothalamus extract to stimulate the reproductive system suggests that calcium is involved in the production or release of releasing factors from the hypothalamus.