The effect of calcium depletion on the chemical composition of bone minerals in laying hens

In a previous experiment (Taylor & Moore, 1954) progressive mineral depletion was induced in pullets by allowing them to lay two, four or six eggs while on a calciumdeficient diet, and the degree of depletion suffered by individual bones was assessed by comparing their total ash content with that of corresponding bones from control birds which did not receive the deficient diet.Great variations were found in the extent to which the different bones had been affected.Whereas, for example, the skull, metatarsi and toes lost only small quantities of minerals, the ribs, sternum, ilia, ischia and pubis suffered severely.In this paper the detailed chemical composition of selected bone materials from these pullets is reported, and the results are discussed in relation to current theories on the chemical nature of bone salts and on the mechanism by which minerals are lost from the skeleton.The bones which, in the depleted birds, experienced severe loss of minerals are termed 'labile' and those which suffered only slightly 'non-labile', and one example of each type of bone and two samples of medullary bone were analysed from each pullet. EXPERIMENTALBirds and their treatment.Eight Light Sussex pullets, judged as being due to lay in about a month, were placed in separate metabolism cages and fed a laying ration containing 2-04y0 Ca.After they had laid three eggs on this ration, six of the birds were given a low-Cadiet (0.054% Ca) by withholding the supplement of calcium carbonate from the standard ration.The other two birds, which were to act as controls,