Before the eggs hatch, they will use a strong flashlight to choose whether the eggs are fertilized successfully. Eggs are usually illuminated by flashing flashlights. If the egg is well polished, the embryo is shaped like a black spot. But experienced farmers will basically see it. When a hen hatches a chick, she usually takes out the eggs that have been hatched for 5 to 7 days and shines them again with a bright flashlight. The purpose of this action is to see whether the hatched eggs and embryos develop and survive. When the eggs hatch between 16 and 18 days, the farmers take out the hatched eggs again and step on the water. This action is to check whether the chicks that are about to hatch are still alive.
Generally speaking, the water used for treading water is warm. You can't check it when it's cold. If it is too hot, the chicken will get hot. So usually the temperature of this water is about 45 degrees. Do the experiment with your own hands, put your hands in warm water, and it is uncomfortable to burn your hands. When it exceeds 80 degrees, the chicken inside becomes hot.
After discovering "bad guys", replace new eggs in time and re-hatch. Because hens are very concerned about holding eggs, they will not hatch completely if there are too many eggs, so they will waste an opportunity to hatch chickens. If they miss it, they will have to wait at least three months. When a hen hatches a chick, if the hatched egg is heated unevenly because of its own size, it will be difficult to touch the bottom egg, which will increase the temperature of the hen and thus affect the hatching progress. Stepping on water and heating eggs evenly help to promote the hatching process.