Hi nuzuki,
The incubator and brooder have two different purposes
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The incubator has to be very strictly temperature and humidity controlled. It is usually a closed system (i.e. sealed, but ventilated) in order to preserve humitidy at 35-50% during the first 18 days if incubation and then 65-70% humidity during the last three days of incubation. This is very improtant so that the egg loses moisture at the correct rate during the incubation process, so that the embryo is neigher too wet (chicks will die due to drowing) nor to dry (chicks will have difficulty hatching as the membranes will adhere to their skin.
It also needs to be kept at 99.5 degrees fahrenheit or 37 degrees celsius for the entire 21 days.
Furthermore, some input from an external source (i.e. you) will be needed to turn the eggs at least three times a day so that the developing embryo doesn't adhere to the inside of the shell.
The incubator simulates the atmosphere created in the nest and under the broody hen.
A brooder box plays a different role altogether. This is the environment in which the baby chicks will live for approximately 5 weeks (though at this time of year, they will probably need artificial heat for 7-8 weeks, at least until the weather improves a little). The brooder box needs to be kept at specific temperatures depending on the age of the chicks, starting at 33degrees celcius, and reducing to approximately 23 degrees celcius over approximately 6 weeks.
Have you thought about what you will do witht he boy chicks which hatch? you should allow for at least 50% of your eggs to be boys. Last year I was really unlucky, and of 60 chicks which hatched, I had over 85% boys
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