Successful incubation depends on maintaining favorable conditions 
for hatching fertile eggs. Four factors of major importance are 
temperature, humidity, ventilation, and turning. Commercial 
incubators are automated to control all of these factors. With small 
incubators, some of these factors must be controlled manually. 

Small incubators that have various degrees of mechanization are now 
available. Some county Extension offices have incubators that may be 
borrowed. It is also possible to build an incubator using plans. 

Temperature must be closely regulated, and the thermometer should be 
at the same level as the eggs. Commercial incubation is accomplished 
at approximately 99.5 degrees F. Temperature can be controlled 
within plus or minus 0.1 degrees F.Small incubators cannot be 
controlled that closely. If control is within plus or minus 2 
degrees F, hatching is usually successful. If the incubator does not 
have a fan to circulate air (still air incubator), the suggested 
temperature is several degrees higher, about 102 degrees F. Follow 
the manufacturer's instructions. 

Sources for incubators.

Bowles Poultry Supplies 
312 O'Connor Road 
Lucasville, OH 45648 
Phone: 614-372-3973 Cutler's Supply, Inc. 
3805 Washington Road 
Carsonville, MI 48419 
Phone: 810-657-9450 

GQF Manufacturing Co. 
P.O. Box 1552 
Savannah, GA 31498-2701 
Phone: 912-236-0651 Humidaire Incubator Company 
P.O. Box 9 
New Madison, OH 45346 
Phone: 800-410-6925 

Nasco Farm Catalog

Make your own. Many 4H publications have them at no or low cost.


Humidity and Ventilation 
The amount of moisture that is in the air is the relative humidity. 
It is usually measured by a wet bulb thermometer. Function depends 
on the cooling caused by evaporating water. A thermometer is covered 
by a cloth sleeve that extends into a container of water. At a given 
temperature, high humidity causes little water evaporation and 
little cooling of the thermometer; therefore, the wet bulb 
thermometer reading is similar to that of the dry bulb thermometer. 
If the humidity is low, much evaporation occurs, resulting in a 
lowering of wet bulb temperature; therefore, the wet bulb 
temperature is much lower than the dry bulb temperature. 

Humidity must be regulated. Commercial incubation maintains a wet 
bulb temperature of about 85 degrees F for the first 18 days for 
chicken eggs and 91 degrees F for the last 3 days. Humidity should 
be set so that an egg loses 13 percent of its initial weight by the 
last 2 days before hatching. Achieving this weight loss by an 
ostrich egg requires a wet bulb temperature of 70 degrees F. Too 
much or too little humidity in the incubator will cause hatching 
problems and the death of embryos. 

If an incubator has too little moisture, the amount can be increased 
by increasing the area of water available for evaporation. A bigger 
pan can be used, or sponges can be placed in the water. The air flow 
through the incubator might also be decreased. Some air exchange 
between the inside and outside of the incubator should happen 
continuously to replace oxygen used by the developing embryos. When 
that need is met, air exchange can be managed according to heat and 
humidity requirements. More air flow tends to lower incubator 
temperature and humidity. 

Turning Eggs 
In commercial incubation, eggs are placed in flats, and the flats 
are automatically tilted back and forth every hour. The purpose of 
turning is to prevent the developing embryo from sticking to the 
shell. For eggs in small incubators that do not have an automatic 
turner, it is recommended that they be turned at least three times a 
day. 

To assist this procedure, place a mark on each egg with a pencil. 
Alternate the position of the mark when eggs are turned. If eggs are 
incubated in an upright position, the round end always should be up 
and the more pointed end down. Beginning at day 18, chicken eggs 
should no longer be turned. 

The need to turn eggs is being re-examined. There is some evidence 
to suggest that eggs need to be turned for only the first half of 
incubation; however, at this time the safest recommendation is to 
turn chicken eggs for the first 18 days of incubation. 

Incubator Operation 
Incubators have been designed to operate in rooms that are 
comfortable for people. If a room is too hot or cold, an incubator 
may not be able to hold the proper temperature. If the incubator is 
in a room where temperatures are decreased to 55 degrees F over the 
weekend, hatchability will be affected. Start the incubator a day or 
two before incubating the eggs. Be certain that it is operating 
properly before incubating the eggs. 

If several people will be involved with the incubation project, it 
is best to keep a written record. 

When the hatch is completed, disconnect the incubator. The chicks, 
shells, and unhatched eggs should be removed and the interior wiped 
clean with a soapy sponge. It should be permitted to air dry for 
several days before using it again or putting it in storage. 

Hatching Problems 
A good hatch from a small incubator is indicated when 70 percent or 
more of the eggs hatch, and the chicks are active and fluffy. It is 
not unusual for inexperienced incubator operators to encounter 
problems. (Turkey eggs have a very low rate for hatching due to low 
sperm counts - I tended to get one chick per 10 eggs and that is 
whay my mentor who specialized in rare heirloom livestocks got as 
well)

One way to follow the progress of incubation is to candle the eggs. 
An egg candler can be purchased, or a flashlight can be used. Hold a 
small flashlight against an egg in a dark room to candle an egg. 
Part of the inside then becomes visible. By 5 days of incubation, 
blood vessels should be visible if the egg has a white shell. If the 
egg has a brown shell, several more days of incubation may be 
required before blood vessels are visible. If development does not 
occur, the eggs may not be fertile, or there may be serious 
incubation problems. By day 8 or 9, the chick may be startled by the 
light, and its movement can be seen. Candling at later stages of 
incubation should show that the embryo is growing and filling up the 
space inside the egg. 

If there are problems with incubation, the chicks that hatch may 
provide clues about the problem. A list of possible problems and 
suggested solutions is given below. Chicks that have not hatched on 
time may be helped. If the shell is pipped (chick has punched a hole 
from the inside) and there is movement, the egg may be examined. The 
shell can be removed in small pieces. If bleeding occurs, the chick 
is not ready. If no bleeding occurs, the chick can be helped from 
its shell. 

Additional information may be collected by breaking the eggs that 
did not hatch. If they are broken onto a flat surface, the contents 
will indicate an infertile egg or show how far development proceeded 
before death. 

Solving incubation problems.

No blood vessels
at candling Eggs not fertile Check flock management 
Embryo died very early Check egg holding conditions 
Check incubation operation 

Many dead embryos Temperature too high or low Check incubator 
and accuracy of thermometer 
Improper turning Turn 3 times per day 
Poor oxygen supply Increase ventilation 
Poor nutrition Check breeder flock diet 

Piped eggs not
hatching Low humidity Have correct wet bulb temperature 

Hatch too early High temperature Check temperature 

Hatch too late Low temperature Check temperature 

Shells stick to chicks High humidity early
or low humidity late Check humidity 

Cripples Temperature problems Check incubator 
Humidity problems Check incubator 
Improper turning Correct turning 
Smooth hatching trays Provide better traction 

Large, soft-bodied
weak chicks Low temperature Check temperature 
Poor ventilation Improve air flow 

Mushy chicks,
dead on tray Navel infection Improve sanitation 

Rough navels High temperature or wide temperature fluctuations 
Check temperature 
Low moisture Check wet bulb temperature 

tenzicut
