The effects of egg weight and shell porosity on the growth and water balance of the chicken embryo

Abstract

1. 1. The combined effects of fresh egg weight and eggshell porosity on embryonic growth and development have been studied in the domestic fowl. 2. 2. At day 12 of incubation there were no marked effects of eggshell porosity or fresh egg weight on the size of the embryo. 3. 3. In the latter part of incubation the eggshell limits gaseous exchange. Hyperbolic functions have been used to describe the increase in dried embryo weight at hatch with increasing eggshell porosity. 4. 4. Water loss from the egg during incubation is in direct proportion to the eggshell porosity. Therefore, when wet embryo weight is being considered, a combination of hyperbolic and linear components is necessary. Wet embryo weight initially increases with increasing shell porosity, but at high porosities begins to decrease. 5. 5. At equivalent eggshell porosities, heavier eggs produce heavier embryos at hatch. 6. 6. The effects of eggshell porosity arid egg weight on the yolk sac mirror their effects on embryonic growth, except that towards hatch the percentage water content of the yolk, rather than the embryo, is constantly maintained.