Observations on the mineral metabolism of pullets: VI. The mobilization of body calcium for shell formation

Abstract

1. Some recent developments of mineral balance studies on laying fowl are discussed and applied to the interpretation of the average results of twenty-six balance experiments with pullets.2. Several of the experiments are re-examined in detail from the same standpoint.3. A tentative hypothesis covering the relations between the calcium metabolism of shell formation and the calcium-phosphorus metabolism of bone is put forward on the basis of this reconsideration of available data. It is suggested that some degree of mobilization of skeletal calcium is a normal feature of shell formation in the fowl, the fraction of bone mineral material mobilized always having a higher Ca: P ratio than the skeleton as a whole, although the actual ratio may vary with the calcium in the diet and with the form in which the calcium is provided.