Factors Affecting the Transfer of Calcium (45 Ca) from the Hen’s Diet to the Egg Shell

INTRODUCTION EXTENSIVE studies on the dietary calcium requirement for laying hens have produced a great amount of information concerning the quantity of this mineral necessary for optimum egg shell formation. There is, however, considerable variation in the findings of different investigators. Norris et al. (1934), Titus et al. (1937), Gutowska and Parkhurst (1942), and Berg et al. (1944) have suggested dietary calcium requirements which varied between 1.6 and 2.1 percent. Later investigators, Petersen et al. (1960), Durham et al. (1960), Harms and Waldroup (1961), Balloun and Marion (1962), and Reddy and Sanford (1963) have shown that higher dietary calcium levels (2.75 to 4.60 percent) were more effective in improving egg shell quality. Driggers and Comar (1949) studied the transfer of calcium from the diet to the egg shell using 45Ca as a tracer. These investigators suggested that 60 to 75 percent of the egg shell calcium was obtained directly from…