Studies on the Calcium Metabolism of Laying Hens

The Relationship Between Blood Calcium and Blood Phosphorus and the Effect of Variations in the Calcium Content of the Ration on Ovulation and Blood Calcium Changes in the Laying Pullet

“…The egg shells became progressively thinner after the calcium was withdrawn from the ration. The data for egg shell weight change under similar conditions are given in a previous paper by Deobald et al (1936). In general, however, there is no correlation between egg shell weight and the level of It seemed advisable at this time to determine whether the delay period before the rise in blood calcium of pullets which were changed from low to optimum calcium rations could be shortened by immediate ingestion of a large amount of available calcium.…”

“…The basal ration used, the method for obtaining blood samples, and the methods for calcium analysis of the blood have been reported (Deobald et al, 1936). The total blood phosphorus was determined by the Fiske and Subbarow (192S) method using hydrogen peroxide to hasten the sulphuric acid digestion of the blood sample.…”

“…TN a previous paper by Deobald, Lease, -*-Hart, and Halpin (1936) it was shown that the blood calcium of the laying pullet does not show any marked variation during an entire laying cycle and that approximately 10 percent of the calcium in the bones of a laying pullet is available for egg shell formation when the calcium is removed from the ration. Feinberg, Hughes, and Scott (1937) and Common (1936) have published data in substantial agreement with these findings.…”

Influence of calcium depletion on medullary bone of laying hens

“…On lowcalcium diet, the only source of calcium becomes the skeleton, which can be severely depleted [11][12][13]. The eggshells become progressively thinner until soft-shelled eggs are laid or laying itself is interrupted [14,15]. Chemical examinations of tissue ashes indicate that structural bone is preferentially destroyed, while medullary bone is maintained in a fairly constant amount [11].…”

The Decrease of Plasma Non-Diffusible Calcium Levels in Starved Laying Hens in Relationship to Shell Deposition and Estrogen ,

“…Charles and Hogben (1933) secretion was in progress; whereas, Knowles et al, (1935) found lower values at the time of shell deposition. Subsequent studies by some of these same investigators (Deobald et al, 1936) and others (Feinberg et al, 1935; showed that total calcium levels remained fairly constant throughout the period of egg formation. However, found significant fluctuations in the diffusible level, particularly during the early stage of shell deposition, which were not of sufficient magnitude to appreciably alter total levels.…”