Calcium and phosphorus balances with laying birds

1. A series of balance experiments to compare calcium carbonate, calcium sulphate and calcium gluconate as sources of calcium for laying hens is described. 2. Not one of the three supplements showed all-round superiority, but calcium sulphate was the worst. 3. The main results indicate that: (a) Calcium sulphate and gluconate cause scouring but carbonate does not. (b) The best retention of calcium occurs with gluconate and the worst with sulphate. (c) Calcium carbonate gives the best shells and calcium sulphate the worst. 4. The experiments also throw fresh light on some more general aspects of calcium and phosphorus metabolism. 5. On the basis of these general results and a review of the literature of blood calcium and phosphorus in laying hens a theory dealing with certain aspects of egg-shell formation is presented.