Candling the Eggs
"Candling" is the examination of the contents of the eggs using a shielded light in a darkened area. Eggs should be checked for development; then, if fertility is poor, you do not have to wait the entire incubation period to learn you are going to have a poor hatch. Candling to check air cell size can determine incubator humidity. You can also observe the development of the embryo.
You can make an egg candler from a wood or metal box or from a container in which you mount a 40-watt light bulb. Make a 1-inch hole in the end near the bulb. For better viewing, place a felt or cloth cushion around the opening so an egg fits the opening better and so light does not leak around the egg.
This egg candle can be made from a tin can that's about 5 inches in diameter and 7 to 9 inches long.
A shortening can with an easily removable lid works well.
Hold the large end of the egg up to the candling light. You won't see much development until the 4th or 5th day of incubation. White or light-colored eggshells permit better viewing of embryo development. The contents of the egg have a pinkish color or cast when the embryo is developing properly. As the embryo grows, it occupies most of the space within the shell. Toward the end of incubation, the contents will appear dark except for the air cell. Eggs that appear clear at 4 to 5 days in incubation or that show little development at 10 days should be removed from the incubator. They are infertile or contain early dead embryos.
Candling will not influence embryo development if you handle the eggs gently. When eggs are removed from the incubator only a few times and are not allowed to cool to any extent, candling makes little difference in hatchability or the time required for hatching.
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Problem-solving
There are many reasons for poor hatches. Breeding, feeding, and management of the egg production flock; care of the eggs before incubation; and the incubation environment: these all can influence the hatch. Possible causes for some of the more common problem symptoms are listed here.
Symptoms Possible cause
Eggs candling clear
No blood rings or embryo growth. Eggs from a flock having no roosters.
Poor flock management.
Eggs stored below 40° F or which were too old before setting.
Eggs candling clear
But showing blood or very small embryos on breaking. Incubator temperature too high.
Eggs stored below 40 or above 80° F. before setting.
Dead Embryos
Before hatching time. Eggs haven't been turned at least 3 times a day.
Lack of ventilation.
Incubator temperature set too high or too low.
Breeder flock having poor hatchability or fed inadequate ration.
Eggs pipped but not hatched (Chick pecks hole through shell)
Chicks dead in shells.
Sticky chicks
Shells sticking to chicks. Low average humidity.
Low average temperature.
Low humidity at hatching time.
Excessive high temperature for short period.
Hatching too early
With bloody navels. Temperature too high.
Delayed hatch
Eggs not pipping until 21st day or later. Temperature too low.
Draggy hatch
Some chicks hatch early, but hatch is slow in finishing. Temperature too high.
Crippled chicks Abnormalities in development.
Poor nutrition of hens.
Incubator temperature too high.
