Calcium Depletion and Repletion in Laying Hens

THE retention of radiocalcium or radiostrontium in bones of humans (Spencer et al., 1961), rats (Cohn et al., 1961) and non-laying pullets (Hurwitz, 1965a), following a single intravenous dose, is reduced by the feeding of high-calcium diets. However, in the laying hen, the severe calcium depletion from bone during calcium restriction (Taylor and Moore, 1954; Hurwitz and Griminger, 1961) would suggest the possibility of reducing the body burden of bone-seeking radiosotopes by calcium restriction. It was the purpose of the present study to investigate the effects of variation in dietary calcium level and sources, and the timing of this variation, on the retention of calcium-45 and strontium-85 in various bone segments, and the deposition of these nuclides in the egg shell. METHODS AND RESULTS General procedure: The method for preparation of samples for analysis was given in detail in the preceding paper (Hurwitz and Bar, 1966). For calcium-45 determinations, calcium …