Variations in the mineral composition of individual bones of the skeleton of the domestic fowl

Abstract

The mineral contents of 15 bones from each of 5 pullets were studied. Two of the birds were killed before the pre-laying storage of bone had taken place, one after pre-laying storage but before the first egg was laid, one after laying 3 eggs on a normal diet and one after laying 6 eggs on a lowcalcium diet. The bones fell into groups according to their citric acid content. The values for one group were all greater than 2 per cent. of the calculated ash and for the other all less than 2 per cent. Bones high in citric acid were ribs, sternum, skull, toes, ilium and ischium; the highest mean was 2.59 for the sternum and the lowest was 2.29 for the ribs. Bones low in citric acid were wing and leg bones, coracoid, scapula and cervical vertebrae; the highest mean was 1.89 for cervical vertebrae and the lowest was 1.44 for femur. There was a tendency for bones rich in citric acid to be rich also in K and there was a significant inverse relation between citrate and carbonate contents. The onset of reproductive activity was associated with increases in Na and carbonate and decreases in Mg and phosphate. No change in bone citric acid was found although plasma citric acid fell from 8.3 to 2.8 mg. per 100 ml. as reproductive activity approached.-R. Hill.