Bad eggs, if they continue to be incubated, are at risk of exploding (due to a buildup of gas). If this happens, the other healthy eggs in the incubator are put at high risk of being contaminated, therefore stopping embryo growth and going bad themselves.
These eggs start appearing around day 18 of incubation when contents may ooze out of the shell pores. When an egg explodes, it releases its contents and bacteria into the air as an aerosol that is distributed across the incubator.
If the inside of the egg is clear - that is, free from visible structures or dark areas - the egg is infertile, or the embryo died very early. Remove this egg from the incubator. If a ring of red is visible within the egg, there was an embryo at some point, but it has died. Remove this egg from the incubator.
Why do incubated eggs go bad? Often, dirty eggs are the culprit. Bacteria from a dirty egg grows inside, turning the contents into a foul liquid, killing any embryo present. Gasses build up and generate pressure that may cause the egg to ooze or explode.
Unfertilized eggs can rot, giving off gases that can affect the other eggs. Rotten eggs can also explode, which is a mess you don't want to clean up.
A "dead germ" can be distinguished by the presence of a blood ring around the embryo. This is caused by the movement of blood away from the embryo after death. If you are not sure whether the embryo is alive, place the egg back in the incubator and retest later.
You'll see blood pumping through the heart of a tiny, developing embryo if you candle a fertile egg on Day 4. If the embryo dies at this point, you may still see a faint network of blood vessels inside the egg's contents. An embryo dying at this point will show a large, black eye.
A loud bang, followed by a very bad smell, are the usual signs. This phenomenon is caused by gas producing bacteria, often Pseudomonas spp., inside the egg. Pressure inside such an egg builds up and even a small vibration can be enough to trigger the explosion.
Close the incubator and DO NOT OPEN until after the chicks hatch. Chicks will begin pipping (pecking through the shell) around the 21st day of incubation. Pipping will take place for 1–6 hours before the chick emerges from the shell. After emerging from the shell, the chicks begin to dry, move about and become strong.
Healthy eggs will be pinkish clear in color, and you can see the embryo inside. You can see some detail visible on the eyes, and you can make out a faint body shape too. This one is obviously dead. Dead eggs look “opaque” or “milky” in color.
Once the nest is “inactive”—that is, there are no viable eggs or live young—it is safe, and legal, to clean out a nest. We recommend disposing of those eggs, deceased young, and/or nest materials (e.g., if you're cleaning out a nest box) in a place where they won't attract insects to the nest area.
This happens when the membrane dries out and literally shrinks around the chick. The chick can't move and so can't hatch. Opening the lid will drop humidity levels massively, which is why it needs to be avoided as much as possible from now on.
This condition can occur quickly (within 1 or 2 minutes) when the incubator is opened to remove or assist other chicks that are hatching. When hatching begins and proper incubator conditions are attained, the incubator should never be opened until after all chicks are hatched and ready for placement in the brooder.
Within a range of 35 to 40.5°C (84.5 - 104.9°F) there is the possibility of eggs hatching. The optimum (for hens) is 37.5 °C (99.5°F), above this temperature as well as a reduced hatch there will be an increase in the number of crippled and deformed chicks. Above 40.5 °C (104.9°F) no embryos will survive.
Your egg will not finish incubating so long as it is cracked. Bacteria will enter through the crack, and the support structure of the shell won't be able to keep the embryo in the correct position. Different aspects of the embryo could get damaged and leak out of the shell as well.
The presence of branch-like structures indicates you likely have a partially incubated egg. If you can't see any defined shapes, it appears solid, or all you can see is an air cell, discard that egg because it's likely gone bad. Likewise, if cracks in the shell are visible when candling, trash it.
Results from this study indicate that properly washed clean or dirty eggs hatch as well as unwashed eggs.
Day 7: First Candling
After 7 days in the incubator you should be able to see some signs of life. Signs of development will typically appear as a dark spot surrounded with numerous blood vessels. If this is what you see, then congratulations, your egg is viable and contains a chicken embryo.
Do all chicken eggs take 21 days to hatch? No. Usually, if temperature and humidity levels have been ideal, the hatchling will start to break through the shell 21 days after the eggs were first set. Bantams will take less long – on average, 18 days.
Incubating large breed chicken eggs usually takes 21 days. Bantam sized are more likely to hatch around day 19 or 20. However, this can vary depending on various things, most importantly the temperature levels in the incubator. If the temperature drops for any reason, the hatch will take longer.
Failed development of an embryo often results in the disintegration and assimilation of its tissue in the uterus, known as embryo resorption. Loss during the stages of prenatal development after organogenesis of the fetus generally results in the similar process of fetal resorption or miscarriage.
Non-Fertile egg, Notice the Germinal spot just above center on the Yolk. It appears as solid white spot. Fertile Egg. Notice the germinal spot looks larger and like a circle in this fertile egg.
Some embryos can survive at temperatures below 90°F for up to 18 hours, so do not give up. You should continue to incubate the eggs after the outage; then candle them 4 to 6 days later to see if there has been further development or signs of life.