Water loss from eggs of domestic fowl and calcium status of hatchlings

Water balance in eggs of domestic fowl was manipulated by drilling holes (each 3 mm in diameter) through the calcareous layer into the air cell on day 10 of incubation. Water loss between days 0 and 18 averaged 6 g for eggs in the control group (no hole) but increased to 8, 12, and 15 g for eggs with 1, 2, or 3 holes, respectively. Hatching success was 79–87% for eggs with 0–2 holes through the eggshell but only 43% for eggs with three holes. Live mass of hatchlings declined as the number of holes drilled in the eggshell increased, but dry mass of carcasses was unaffected by the treatments. The quantity of Ca²⁺, Mg²⁺, and phosphorus in residual yolks and yolk-free carcasses of hatchlings was not influenced by the amount of water lost from eggs. Plasma Ca²⁺ and Mg²⁺ were elevated in hatchlings from eggs with high rates of water loss. The inability to regulate plasma Ca²⁺ may be a negative consequence of excessive water loss and could contribute to increased mortality of embryos.