From Egg To Chick:
Incubation Procedures
OBTAINING HATCHING EGGS
Obtaining fertile eggs may present a problem,
especially if you live in an urban area. Most of
the eggs sold in grocery stores are not fertile
and cannot be used for incubation. Fertile eggs
can usually be obtained from hatcheries or poultry
breeding farms. Look in the yellow pages of your
telephone directory for names of hatcheries and
poultry breeders. Or contact the farm adviser in
your county agricultural extension service office
for suggestions.
If possible, pick up the eggs yourself rather
than have them shipped or mailed. It is difficult
for hatcheries, post offices, and transportation
companies to handle small orders of eggs
properly.
CARE OF EGGS PRIOR TO INCUBATION
The hatchability of eggs can be severely reduced
by improper care prior to incubation. Since it may
not be practical for you to put the eggs in an
incubator as soon as you get them, protect them
from extreme variations in temperature. Ideally,
eggs should not be more than 7 days old when they
are set (placed in incubator). Beyond that point,
hatchability declines.
If it is necessary to hold the eggs before you
set them, turn them daily and keep them in a room
where the temperature is around 50o
F (10 C) and the relative humidity is 70 to 80
percent. The vegetable section of your refrigerator
could be used for holding the egg until it is time
to place them in the incubator. Temperatures below
40o F (4 C) reduce hatchability. Under no
circumstances should the eggs be held at room
temperature, because temperatures of this level are
detrimental to hatchability. Embryos will begin
develop at subnormal rates when the temperature
reaches about 80o F (27 C)
LOCATION OF INCUBATOR
Locate your incubator in a room in which
temperature is between 70o and
75o F (21 and 24 C), and which free from
drafts and excessive variations in temperature. Do
not place the incubator near windows where it will
be exposed to the direct rays of the sun. The sun's
rays may raise the temperature so much that all of
the embryos will be destroyed.
READYING THE INCUBATOR FOR
OPERATION
Before you set the eggs, be sure that the
incubator is in good working order. Put some warm
water in the water pan, place each thermometer so
that the bulb of the thermometer is 1 inch (2.5
cm) above the screen, cover the incubator with the
pane of glass, and then operate the incubator
until the temperature inside it holds at
99o to 103oF (37 to 39 C).
Adjust the thermostat to control temperature in
an incubator with a commercial heating unit. In an
incubator with a light-bulb unit, control the
temperature by adjusting the size of the opening
at the top by moving the pane of glass back from
the edge of the incubator, unless a thermostat has
been installed. If you are using a plywood
incubator, adjust the openings as necessary. Or in
either incubator you can adjust the heat by using
bulbs of different sizes. Forty-watt bulbs will be
about the right size for most incubators. Make
certain that the sides and top of the incubator
fit closely so that no heat is lost. You may need
to make many adjustments to reach a proper
setting.
PREPARING THE EGGS FOR INCUBATION
Eggs must be turned while in the incubator, so
before you put in the eggs mark them with a pencil
so you can tell when they have been properly
turned. An excellent method is to put an "X" on
one side of the egg and an "0" on the opposite
side. Then you can always tell when the eggs have
been turned, because either all "0" 's or all
"X"'s are turned up at the same time.
HUMIDITY
Nature has provided that the eggs shall dry out
to some extent during incubation (Fig. 4). This
loss should be about 11 percent of the original
weight, but more than this is detrimental. Water
must be placed in the incubator to avoid excessive
moisture loss. Keep a pan of water inside at all
times. The surface area of the pan should be about
as large as the of eggs.
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Size of the air cell in the egg on the 7th,
14th, and 18th days of incubation. (Fig. 4)
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The amount of opening in the incubator also
influences the level of humidity. When the
humidity is too high, open the vents all the way
on the plywood incubator or slide the glass
further back on the cardboard incubator. When
humidity is too low, the openings should be more
nearly closed, but never completely so. Weather
conditions will affect the relative humidity in
the incubator.
The ideal moisture level is about 50 to 55
percent relative humidity (83o -
87o F (28 - 31 C) on a wet bulb
thermometer) for the first 18 days and about 65
percent (89o - 90o F (31 - 32
C) wet bulb) for the last 3 days. Excessive drying
because of low humidity will cause the chick to
stick to the shell and fail to survive. Some
variation above or below the ideal level usually
will not affect hatchability
drastically. Frequently, school incubators have too
much ventilation and, therefore, too little
moisture. This results in delayed or reduced
hatches.
When you refill the water pan, use warm
water. Hot or cold water will affect the
temperature of the incubator too much. To increase
the humidity level the last three days, set an
extra pan of water in the incubator. Or you can
put a wet sponge in the incubator to raise the
humidity. A word of caution: Do not let the eggs
come into direct contact with the water at any
time.
TEMPERATURE
Temperature in the still-air incubator can vary
from 99o to 103o F. (37 - 39
C) with no harmful effects if the temperature varies
between these limits rather than staying at either
extreme. If it stays at either extreme for several
days, the hatch may be reduced somewhat. Overheating
is much more critical than underheating. Overheating
will result in abnormal embryos, speed up
development, and lower hatchability. A thermometer
should be in the center of the incubator if
possible, and the bulb of the thermometer should be
level with, but not touching, the tops of the
eggs. If light bulbs are used to supply the heat
they should be distributed as evenly as possible in
the incubator.
VENTILATION
Proper ventilation is very important during the
incubation process. While the embryo is
developing, oxygen enters the egg through the
shell, and carbon dioxide escapes in the same
manner. As the chicks begin to hatch, it is
essential that they receive an increasing supply
of oxygen. This means that the air openings need
to be opened gradually to increase the flow of
air.
LENGTH OF INCUBATION
Chicken eggs require 21 days to hatch, but the
incubation period for the eggs of other species of
poultry varies. The approximate periods of incub a
tion required for various species of poultry and
game birds are:
|
Days
|
Chicken . . . . . . . . . . . . . . . . .
. . . . . .
|
21
|
Turkey . . . . . . . . . . . . . . . . .
. . . . . . .
|
28
|
Duck . . . . . . . . . . . . . . . . . .
. . . . . . .
|
28
|
Muscovy duck . . . . . . . . . . . . . . . .
|
33-35
|
Goose . . . . . . . . . . . . . . . . . .
. . . . . .
|
29-31
|
Guinea . . . . . . . . . . . . . . . . .
. . . . . .
|
26-28
|
Pigeon . . . . . . . . . . . . . . . . .
. . . . . .
|
16-18
|
Ring-neck pheasant . . . . . . . . . .
|
23-24
|
Mongolian pheasant . . . . . . . . . .
|
24-25
|
Bobwhite quail . . . . . . . . . . . . . . . .
|
23
|
Japanese quail . . . . . . . . . . . . . . .
|
17-18
|
Chukar partridge . . . . . . . . . . . . . .
|
22-23
|
Peafowl . . . . . . . . . . . . . . . . .
. . . . .
|
28
|
TURNING THE EGGS
When the eggs are put in the incubator, lay them
on their sides and turn them at least three times
a day. Turning prevents the embryo from sticking
to the shell membranes as it will do if it is left
in one position too long. Good results can be
obtained by turning the eggs the first thing in
the morning, again at noon, and the last thing at
night. But it is better to turn the eggs more than
three times a day. In any case they should be
turned an odd number of times so that the side
that is up longest will be staggered from day to
day. Otherwise the egg will be in the same
position every night, which is the longest stretch
of time between turns.
When you turn the eggs, move them to a different
part of the tray to offset variations in
temperature in the different parts of the
incubator. Continue to turn the eggs from the
first through the 17th days but do not turn them
after the 17th day.
TESTING THE EGGS
Although it is not necessary to test eggs for
fertility, you can eliminate the eggs which are
not going to hatch by doing so. It is also an
interesting phase of the project, since it is
possible to see clearly the developing embryo.
Get a shoe box or a box of similar dimension made
from wood or tin and cut a hole in one end about
one inch in diameter. Use an extension cord and
mount a 60-watt bulb in the box. Darken the room
and hold the large end of the egg to the
light. What you will see depends mostly on the age
of the embryo. It is difficult to see much
development until the 4th or 5th day of
incubation.
The first parts of the embryo which you will be
able to see by candling will be the head and eye,
and they will appear as a dark object. If the
embryo is alive and circulation is established,
the contents of the egg will have a pinkish color
or cast. But if the embryo is dead the contents
will appear muddy or brownish.
The live and growing embryo will eventually
occupy all of the interior of the egg and will not
transmit light; thus, it will be impossible to see
anything but the air cell at the end of the
incubation period. Infertile eggs and early dead
embryos can be detected readily because they
appear clear.
Removing the eggs from the incubator for candling
does little harm if you handle them gently. It may
slow up development of the chick, though,
depending upon how much the egg is
cooled. Generally, if the eggs are removed from
the incubator two or three times for a period of
no more than 15 minutes each, such cooling will
make little difference in the total incubation
time required for hatching. On the other hand, if
the eggs are cooled for several hours because of
power failure or some other reason, hatching time
may be delayed. It is as important not to cool the
eggs too long as it is to avoid overheating.
FINAL STAGES OF INCUBATION
After the 17th day, eggs should not be turned,
and the incubator should not be opened unless it
becomes necessary to add water, replace a light
bulb, or make some other necessary
adjustment. Chicks will start to pip the shell
around the 19th day. All chicks which are going to
hatch should be out of their shells by the 21st
day. If the eggs were chilled or you ran into
operational difficulties during the incubation
period, the hatch may be delayed. Chicks that
hatch beyond the 22nd day are usually not healthy,
vigorous ones.
When most of the eggs are hatched, lower the
temperature to approximately 95o> F (35
C). This permits the newly-hatched chicks to dry
off. At this time, all the air vents in the plywood
incubator should be opened, and the glass top on the
cardboard incubator should be opened wider.
HOW THE CHICK EMERGES FROM THE SHELL
The head of the chick develops at the large end
of the egg. Between the 15th and 16th days, the
chick orients itself so that its head is near the
air cell at the large end of the egg. Not long
before the chick is ready to attempt to make its
way out of the shell its neck acquires a double
bend so that its beak is under its right wing and
pointed toward the air cell. About the 19th day
the chick thrusts its head forward. Its beak
quickly breaks through the inner shell membrane,
and the chick's lungs begin to function. Complete
breathing by the lungs usually does not occur
until the 20th day of incubation.
Using its egg tooth (a tiny, sharp, horny
projection on the end of its beak), the chick
pecks at the shell thousands of times. Finally,
the young bird pips its way through the shell and
begins to breathe air directly from the
outside. After the chick has made a hole in the
shell, it stops pipping for three to eight hours
and rests. During this time, it is acclimating its
lungs to the outside atmosphere. After the resting
stage is completed, the second stage of pipping
begins.
The chick begins to turn slowly inside the
egg. As it turns, usually counter-clockwise, the
cutting edge of the chick tooth continues to chip
away. In two to five hours, the chick has made
about three quarters of a turn inside the egg. As
the chick progresses in its movement around the
shell, it begins pushing on the egg cap (large
end). Squirming and struggling, the chick works
feverishly for about 40 minutes pushing at the
cap. Finally with a vigorous shove, the chick
breaks free from the shell, still wet and
panting.
When the chick is freed completely from the
shell, it lies still. Its energy has been
virtually exhausted, and it is extremely
tired. After a rest of some few minutes, the chick
begins to rise to its feet and gain coordination
of its muscles. Within a few days the egg tooth,
its usefulness over, will disappear.
REASONS FOR POOR HATCHES
Infertile eggs.
Eggs too old when
set.
Parent stock weak,
unhealthy, or fed a nutritionally
deficient diet.
Improper care of eggs prior
to incubation.
Shell
contamination.
Eggs not turned often
enough.
Temperatures too high, too
low, or too variable during
incubation.
Too little humidity in the
incubator or occasionally too
much.
Improper
ventilation.
Oxygen starvation.
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WHAT TO
DO AFTER THE CHICKS HATCH
As soon as the chicks have dried and fluffed up
completely, remove them from the incubator and
place them in holding quarters where the
temperature is approximately 95o F (35
C). Then give them fresh water and feed. Rearing the
chicks as a project has certain limitations, but if
they are to be kept for a few days, they should be
given a chick-starting mash obtainable at any feed
or farm supply store. Fresh water is also
important.
Since the disposal of day-old or started chicks
may be difficult, have the solution to this
problem worked out before you undertake this
project. If you are going to rear the chicks at
home, secure your parents' permission and
cooperation in advance.
Cleaning the incubator. When the hatch is
completed, disconnect the incubator. Remove all
shells and unhatched eggs and wipe the interior
clean with a soapy sponge. Permit the incubator to
air dry for several days by leaving the door
open.
Cleaning can be made easier if you place a layer
or two of cheesecloth or crinoline on the rack on
the 17th or 18th day of incubation to catch the
egg shell and other debris. This will also help to
prevent injury to the chicks' navels. After the
chicks are removed the cheesecloth can be
discarded.
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