Egg Sandwich
Posted by val williams on May 3, 2005
Q: HI. We are in the process of hatching chicken eggs and ducklings in a reliable incubator in a 5th grade classroom. We weighed the eggs before we set them and again today, after a week. The eggs that we have determined to be fertile have lost between 2 - 3 grams of wieght. Is this normal? And what would the explanation behind it be?
A: Val, this is a good observation. Yes, I think weight loss like what you describe would be normal. Everything a developing chick embryo needs to grow must be present and available to the embryo at the time the egg is laid, except oxygen and water vapor (which pass through tiny pores in the shell into the egg as the embryo develops). Most of this food is in the yolk. A fast-growing chick embryo uses up this food supply, and produces waste products. Some of these waste products stay inside the egg until it hatches, but others leave the egg through those pores I mentioned. These include carbon dioxide and water vapor. Both these gases have mass, and probably account for the weight loss you have observed.
Mark Baldwin ( May 3, 2005)