Husbandry Chapter VI: Hatching
Eggs and Incubation
Healthy chicks come
from good breeders. Breeder nutrition, uniformity and the vaccination program are
Flock Health, Age And Nutrition
A healthy breeder
flock, females with a good rate of lay mated to vigorous males, will usually
produce highly fertitle eggs that hatch well under good incubation practices.
Hatching eggs from new breeder flocks (just starting to lay) do not hatch as
well as eggs from those that have been laying for three to four months.
Hatchability of eggs from old breeders nearing the end of their laying period
A hatching ration
should be fed to breeders for about three weeks prior to saving eggs for
incubation. The extra vitamins and minerals that it contains, as opposed to a
laying ration, are essential for good hatchability. Sometimes, poor hatching
results occur when a lower priced laying ration is used. The nutritional
requirement of the breeder hen must be adequate for optimum hatching and good
sanitation, nest box sanitation and hatching egg care are important to the
production of healthy chicks. Nest material must be clean and dry and free of
contamination. It should be cleaned daily (remove dirty material and
droppings) and replenished or changed weekly. Para-formaldehyde pellets
(20-25 g per nest, per month) will improve nest-box sanitation.
require a clean area where eggs can be cleaned, selected for quality and
placed large end up on hatching trays. The temperature of this room should
not be less than 21BC. If eggs are stored on the farm, temperature and
humidity must be controlled.
And Care Of Hatching Eggs
Set only clean eggs.
If eggs are soiled, it is preferable to clean them with sandpaper & egg
brush. If hatching eggs are washed, the temperature of the water must be 43
to 44BC. The eggs should be spray washed with detergent, sanitized and
fan-dried. Improperly washed eggs may rot or explode during the incubation
period. Dirty eggs can be reduced if the eggs are gathered four or five times
daily from nests supplied with fresh, clean nest material and if the litter
in the breeding pens is kept dry so the hens feet are clean. Do not set floor
eggs. Collect eggs with clean hands onto clean flats.
Select hatching eggs
that are uniform in size (recommended minimum 52g for meat-type), shape and
colour, with good sound shells. Do not set malformed, porous-shelled,
doubled-yolked eggs or eggs with cracks. Shells that have a mottled
appearance upon candling are not considered to have poor shell quality and
can usually be set with good hatching results.
Since smaller eggs
hatch in less time than large eggs it is recommended that eggs be separated
by size and that small eggs be put in the incubator 8-18 hours after the
larger eggs are set.
percentage will be the highest if eggs are held at a temperature of 16 to
17BC for not more than one week before setting. Higher temperatures initiate
embryo growth. Storage temperature should be reduced to 13BC if eggs are
being held for two weeks or longer. Eggs may sweat when moved to warm, humid
areas. This allows bacteria to penetrate the shell. Turning eggs during the
holding period is not beneficial. It has been shown that eggs held for more
than 2 weeks hatched better when stored small end up (contrary to the
accepted traditional large end-up postion). Relative humidity should be
maintained at approximately 80% in the egg holding room. Higher humidity
encourages mold growth. Prior to placing eggs in the incubator, they may be
removed from the egg storage room and warmed to room temperature for
approximately 6 hours.
In the selection of
a successful incubator room, factors such as heating, humidity, ventilation,
and sanitation should all be considered. Optimum results can be expected if
the temperature can be maintained at between 24 and 27BC, with uniform
humidity below the level that is required in the incubator. Tropical climates
(heat & humidity) make it difficult to maintain good incubator room
conditions. Good ventilation and a constant supply of oxygen to remove excess
carbon dioxide from the environment surrounding the incubating eggs is
necessary for the developing embryo. High altitude reduces available oxygen.
An incubator should
not be placed near an outside wall or window in cold climates or in direct
Incubators are the
most important equipment in the hatchery process. Many kinds of incubators
are manufactured; however, the general principles of all modern machines for
commercial hatchery production are the same. Incubator setting capacity
ranges from approximately 14,000 to 100,000 eggs.
the hatching eggs are set vertically, with the large ends up in trays or flats in a setter and
turned mechanically until about three days prior to hatching (setting
period). The eggs are then transferred to a hatcher (hatching period) in a
horizontal position and not turned during the hatching process. Both setters
and hatchers have forced-draft air circulation, automatic temperature,
humidity and cooling controls.
For small backyard
poultry operators, there are small, still-air machines. Capacity of these
incubators varies from 12 to 200 eggs. The eggs are set in a horizontal
position and are usually turned manually. This type of incubator may be used
for the entire incubation period for any kind of eggs. The source of heat is
a thermostatically controlled heating element or light bulb. Humidity is
supplied in most cases by water in a pan below the eggs, and ventilation
controlled by small air vents or holes. Most still-air machines have
transparent plastic domes through which the incubation process can be
Incubation Time for some Common Avian
- 21 days
- 28 days
- 17 days
- 26 days
- 24 days
- 28 days
- 35 days
- 28-32 days
- 35 days
Principal Factors In Incubation
The five main
factors affecting incubation, listed in order of importance are: temperature,
humidity, ventilation, position, and turning of the eggs.
Some factors to
consider before purchasing an incubator:
1. Any incubator
will produce better results when operating at capacity. Egg capacity is a
2. How long the
incubator will last and cost of all replacement parts;
3. Service and
availability of parts;
4. Accuracy of
controls, to keep temperature and humidity fluctuations to a minimum;
5. The amount of
labour involved in operating the machine and carrying out a thorough
6. The guarantee.
Hatching eggs may be
warmed to a temperature of 25 to 30BC, prior to setting. The normal
development of the embryo is dependent on the heat being held within a very
narrow range in the incubator. In small still-air incubators, the temperature
of the upper surface of the egg is higher than on the lower surface, while in
large incubators, the air movement maintains the same temperature over the
entire surface. For this reason, a still-air incubator must be operated at a
higher temperature than a forced-draft incubator.
In small still-air
incubators, a constant temperature of 39BC is considered satisfactory to
produce good hatching results. The temperature may vary between 37.5 and
39.5BC without hurting the embryos as long as the temperature does not remain
at either extreme. These readings should be taken with the bulb of the
thermometer level with the upper surface of the eggs, but not in contact with
the egg shell. A standing thermometer will give a more reliable reading than
a hanging thermometer and the thermometer must be accurate. The temperature
may rise one degree at hatching time without causing any reduction in hatch
In large incubators,
the temperature, humidity, and speed of air movement are very closely
dependent on each other, and since air speed varies in different incubators,
it is impossible to state an exact operating temperature for all large
machines, but generally it is around 37.5BC for a setter and 37BC for a
hatcher. Follow the manufacturer's instructions closely with regard to
temperature and ensure that instructions are for the model in use. High
temperatures even for a very short period of time during any part of the
incubation period will cause more harm than low temperatures.
Factors May Contribute To High Or Low Incubator Temperatures.
or low room temperatures or floor temperature under the incubator affect the
operating temperature of both large and small incubators. A large incubator
placed near an outside wall may have one section operating at a lower or
higher temperature than the other. These problems and those listed below will
result in one group of eggs hatching earlier or later than the others,
increased embryo mortality or cause leg deformity in chicks & poults.
temperature variation because of drains causing cold or heat under the
incubator thermometer not reading correctly.
failure of automatic equipment such as thermostats, cooling coils or
air circulation leading in turn to a rise in temperature in part of the
incubator, because of: a decrease in fan speed, usually caused by low voltage
or a slipping fan belt; incorrect spacing of filled egg trays in a partially
an incubator for any one setting of eggs.
incubation or setting period, eggs should lose 11 to 12% of their weight
(another 3 to 4% in the hatcher, after day 18), due mainly to a loss of
moisture. The amount of moisture (humidity) in the incubator controls the
rate of evaporation from the egg. The evaporation rate is also related to
temperature, air speed, shell thickness, and size of eggs; the smaller the
eggs, the greater percentage of moisture loss. Too great a moisture loss from
the egg in the early stage of incubation will cause the embryo to adhere to
the shell, causing death. Insufficient evaporation may cause death from lack
of oxygen because of a small air cell, since just prior to pipping the shell,
the embryo pips into the air cell and starts to breath air. The best guides
to the correct amount of humidity in an incubator is the weight loss and the
size and enlargement of the air cell during incubation, or the position at
which the chick pips the shell. The degree of enlargement of the air cell
should be determined by candling several eggs and estimating the averagee
The amount of
moisture in an incubator may be referred to as "relative humidity",
which is a percentage of the moisture in the air at any given temperature.
This can be measured by a wet-bulb thermometer. The relationship between
dry-bulb air temperature, wet-bulb readings and relative humidity is shown in
A wet-bulb reading
is based on air movement, and for this reason, a wet-bulb thermometer cannot
be used to determine the amount of humidity in a still-air incubator. The
relative humidity for small incubators is usually stated as 60%. Other
inexpensive but less accurate equipment is available to measure relative
humidity. A level water pan on the floor of the incubator under the eggs
during the entire incubation period will generally supply sufficient moisture
to give good hatching results, provided the moisture content of the air in
the environment is neither too high or too low. Percent egg weight loss
during the setting period can act as a guide to the correct humidity. This
can be done by weighing some eggs at the start of incubation and the same
eggs again on the 7th and 18th day, and calculating the loss that occurred
(write the weight on the shell with a pencil). Chicken eggs should lose approximately
4.5% and 11.5% during the first 7 and the first 18 days of incubation
than 0.34 mm are too thick and humidity should be reduced to increase
moisture loss. Below 0.31 mm is too thin. Normal would be 0.33 to 0.34 mm at
the beginning of production. Shell thickness decreases with age of breeder
hen with 0.31 mm normal at 60 weeks.
In large incubators,
the temperature, air speed and humidity are intimately related, and the
manufacturer’s instructions should be followed closely. Better hatching
results may be obtained if the temperature is lowered and the humidity raised
at hatching time (only if separate hatching compartments are available).
Lowering the air temperature will provide an additional increase in relative humidity
to keep shell membranes moist during the hatching process.
TABLE 1. PERCENT RELATIVE HUMIDITY AT
DIFFERENT WET-BULB READINGS
Relative Humidity (%) at Air Temperature of
Incorrect humidity may
be due to a number of factors, the more important of which are listed below:
environmental humidity in tropical countries.
2. A wet-bulb
thermometer reading incorrectly. Remove the wick to determine whether the
thermometer is reading the same as the dry-bulb thermometer.
3. Dust and dirt on
the wet-bulb wick. Change wicks often and use only distilled water in the
4. In small
incubators with humidity supplied by water pan evaporation, ensure that there
is always an adequate amount of water in the pan, as the rate of evaporation
is dependent on the humidity in the room. The lower the humidity in the room,
the higher the evaporation and vice versa. During hatching fluff settles on
the surface of the water producing a film that causes a reduction in the rate
of water evaporation necessary for optimum hatchability. Clean the water pan
daily and replace with clean, lukewarm water.
5. Ventilating an
incubator to control temperature will lower humidity in a dry environment
unless automatic humidifiers are being used in the incubator room.
6. If airflow in
incubators is not uniform humidity may be different from bottom to top or
side to side.
The free movement of
oxygen, carbon dioxide and water vapor through the pores of the shell is
important, since the developing embryo must be able to take in a constant
supply of oxygen and release carbon dioxide and moisture. Oxygen content of
21% (present in air at sea level) and a carbon dioxide content not exceeding
0.5% in the air are considered optimum for good hatching results. Room
temperature, room humidity, the number of eggs set, the period of incubation,
and the air movement in the incubator all influence ventilation requirements.
Ventilation problems are not the same in small incubators as they are in
large incubators, where a large number of eggs are set in a very small space.
During the early
part of the incubation period, ventilation in small incubators may be held to
a minimum. However, during the hatching period additional ventilation must be
supplied to reduce the carbon dioxide in the incubator. It is advisable not
to increased ventilation until half of the hatch has been completed, since ventilating
too soon will reduce the humidity. In large incubators, the manufacturer's
directions should be followed, however, ventilating recommendations may not
be applicable to every locality and every room condition.
If ventilation is
used to control either temperature or humidity in the incubator, the control
of the same factors in the incubator room are important. At a room
temperature below 18 C, ventilating an incubator will reduce both temperature
and humidity. In a room with high humidity, (tropical countries) the primary
concern is to maintain the correct temperature.
The main ventilation
consideration may be summarized as follows:
1. Ventilation is
more important in large incubators than in small incubators.
2. The amount of
ventilation required may be altered by atmospheric conditions.
3. Ventilation is
very important in any incubator at hatching time. Insufficient ventilation
may result in embryo or chick death.
4. Ventilation in
excess of the recommended amount may be applied to reduce temperature or
5. The appearance of
chicks panting in a hatcher at
normal temperature is an
indication of a rise in the carbon dioxide content of the hatcher air. Under
such conditions chicks must breathe faster to obtain the required amount of
oxygen and to eliminate the exceses carbon dioxide. If excessive panting
occurs, increase the airflow in the hatcher.
And Turning Of Eggs
In small incubators,
the eggs are maintained in a horizontal position during the entire incubation
period. In large incubators eggs should be placed in a vertical position,
large end up, during the hatching period. In small incubators, the eggs are
moved when turned, while in large incubators they remain in a stationary
position on the incubator tray and the egg tray is turned through an angle of
not less than 90 in opposite directions with each turning. The objective is
the same in both types of incubators; namely, to prevent the embryo from
sticking to the shell membranes. Turning also ensures a complete contact of
the embryonic membranes with the food material in the egg, especially in
early stages of incubation.
In small incubators,
the eggs should be turned at least four times daily. It is advisable to leave
some space on the tray to allow for moving the eggs forward a 1/2 turn on one
turn and back a 1/2 turn on the next, thus making sure that all the eggs
move. Eggs shouldnot be
turned in a complete circle, as this has a tendency to rupture the allantois
sac with resultant embryonic mortality. Wash hands carefully before turning
eggs to avoid bacterial contamination of the shell. In large incubators, the
trays are usually turned hourly with all the egg trays moving at one time.
For good hatchability, eggs should be turned to a position at least 45 from
vertical, then reversed in the opposite direction to a similar position. In
the most recent models of incubators, eggs are turned through an arc of 150 and
in a few models they are turned as far as 180 . The introduction of these
newer methods of turning eggs has been an important aspect in improving
hatchability. Eggs should not be turned in either large or small incubators
during the hatching period. The greatest benefit from turning eggs is during
the first week in incubation.
Factors Affecting Incubation
hatching eggs do not hatch as well as eggs of good quality. The term
"quality" refers to the condition outside the shell, the condition
of the shell itself and that of the contents. Eggs with inferior
characteristics, as discussed in "Selection and Care of Hatching
Eggs," should not be set.
Eggs used for
hatching should be clean and stored in clean containers in a sanitary egg
holding room. Eggs contaminated with bacterial organisms usually do not hatch
well and this poor quality is reflected in the chicks that do hatch.
Rough handling of
hatching eggs before they are set will increase the number of dead embryos,
with mortality occurring between the 4th and 13th day of incubation. Also,
jarring eggs during incubation may result in the rupture of the egg shell
membrane and thereby lower hatchability.
in temperature and humidity during storage will have a major adverse affect
on hatchability. Refer to "Selection and Care of Hatching Eggs" for
proper egg storage procedure.
If the interior of
an incubator is painted or varnished, or if the trays are varnished, the
percentage of hatch will be reduced, possibly by as much as 25%. This adverse
effect disappears in about 30 days, suggesting that the ill effect is
eliminated by oxidation of the paint.
This problem may be
overcome without any reduction in percentage of hatch if the incubator is
fumigated with formaldehyde gas at the concentration recommended for proper
hatchery fumigation. The gassing should be done as soon as the paint is dry
and with the incubator operating at recommended temperature and humidity for
The addition of
automatic equipment has eliminated many of the problems with incubators,
however, such hazards may occur when automatic devices fail. During hatching
all automatic devices, such as cooling coils, automatic dampers, tray
turners, alarm bells, etc., should be checked at regular intervals.
Electrical failure may require that automatic equipment be reset. After an
incubator is purchased, it is important to know how every part operates.
eggs on the 7th and 18th day of incubation, may be recommended for small
poultry producers. Egg candling will detect infertiles and early dead germs.
Therefore, problems within the hatching flock can be identified without
waiting until the incubation period is completed.
instructions outlined in "Fumigation Procedure". Excessive
and improper fumigation can result in high mortality in developing embryos.
The killing of
bacterial organisms by formaldehyde gas is based on the concentrations of the
gas, exposure time, temperature, and humidity of the incubator. The chemicals
potassium permanganate and formalin (which is 40% formaldehyde gas) have
proven to be the most effective method of destroying bacterial organisms in
the hatchery. To accomplish the proper release of the gas, one and one-half
parts (by volume) formalin is added to one part (by weight) of potassium
permanganate. This will release the formaldehyde as gas or fumigant. When the
reaction is complete, a dry, brown powder will be left. If the residue is
wet, not enough permanganate was used; if the residue is purple, too much
permanganate was added.
concentration for effective fumigation is 53 mL of formalin added to 36 g of
potassium permanaganate per cubic metre of space to be fumigated, or 1 1/2 mL
of formalin added to 1 g of potassium permanganate per cubic foot of space to
Caution: Never add
the permanagante to the formalin. Heat is generated when the two chemicals
are combined, and care should be taken. Formaldehyde gas is generated
quickly. Do not allow the fumes to get into the eyes. Personnel should use a
respirator or wear a mask to avoid unnecessary exposure. Ventilate the
incubator room to remove fumes that escape from the incubator.
It is not
recommended to fumigate setters with hatching eggs in them, but if such
treatment becomes necessary, embryos between 24 and 96 hours of age should
not be exposed to the above concentration of formaldehyde. Hatching
compartments should be fumigated after the eggs are transferred from the
setter to the hatcher, again after the hatch has been taken off and before
the refuse has been removed from the trays, and finally after the hatcher has
been thoroughly cleaned. Do not fumigate chicks with this concentration of
formaldehyde gas. Small still-air incubators should be fumigated after the
chicks have been removed and prior to discarding the refuse from the tray and
again after the incubator has been thoroughly cleaned.
1. Make sure the
temperature and humidity of the incubators are at normal operating
2. Measure the
inside volume of the machine in cubic feet or cubic metres (length x width x
3. Close the
ventilators, but leave the fans on.
4. Weigh the
required amount of potassium permanganate into a wide enamelware or
earthenware vessel large enough to accommodate the boiling and splattering
action experienced when the formalin is added. Place the vessel and the
permanganate in the area to be fumigated; then add the formalin.
5. Close the door
immediately and leave closed for 20 minutes.
6. After 20 minutes,
open the ventilators.
7. Open the doors of
the machine for five minutes, leaving the fan on to allow more of the
formaldehyde gas to escape, or neutralize it with a 25% solution of ammonium
hydroxide equal to one-half the amount of formalin used. The hydroxide should
be thrown directly on the floor of the machine and the doors closed. The
formaldehyde gas will quickly be neutralized.
Fumigation Of Hatcher
increase in bacterial organisms occurs during the hatching period. These can
be reduced, but not completely eliminated, by slow release of formalin in the
hatcher during the last 48 hours of the hatching period.
fumigation to be effective, hatching eggs should also be fumigated at
transfer time with the recommended concentration.
Place formalin in
pan about 25 mm in depth, allowing 58 cm2 of pan for each cubic metre of
hatcher space, or a pan about 1 in. deep, allowing 30 in2 of pan for
approximately 1000 ft3 of hatcher space. Do
not use permanganate. The pan should be placed in the open area of the
hatcher in direct line with the airflow.
Place the pan of
formalin in hatcher 48 hours prior to hatch completion. To overcome fluff deposited
on the formalin, add more formalin about 24 hours before hatch is complete to
If the fan stops
(mechanical failure etc.) and reduces the airflow, remove the pan of formalin
immediately. If hatchers are only partially full, continuous fumigation is
not recommended, as a reduction in airflow will create an excessive build up
of formalin in the hatcher.
1. Properly carried
out, fumigation should not affect hatchability.
2. Fumigation will
only kill bacteria that are present on the surface of hatchery refuse.
Fumigation will not kill bacteria inside unhatched or pipped eggs. It is
important to dispose of hatchery refuse carefully to minimize hatchery
3. The hatchery room
must be separate from the tray dumping room and from the chick processing
area. Air flow and traffic must be controlled to prevent contamination of the
chick processing and holding areas.
fumigation along with other sanitary measures should control navel infection
5. Fumigation is not
intended to replace a thorough cleaning program.
Hatchery layout is
important to a good sanitation program. Arrange the hatchery so there is a
one-way flow of material from the point where the hatching eggs are brought
in to where the processed chicks go out.
Hatcheries should be
designed so the flow of eggs, chicks and personnel does not spread
contamination from one room to the next. Doors, including one-way doors, help
stop cross contamination between rooms. Positive air pressure prevents
contamination through an open door. Workers should change outer clothing and
wash hands before moving from one work station to another.
SUMMARY OF SOME
1. Feed breeder
flock hatching ration that is well fortified with essential nutrients.
2. Use healthy
3. Provide good
4. Avoid holding
eggs in storage for more than one week.
5. Prewarm eggs for
6 to 8 hours at incubator room temperature.
6. Set clean, good
quality eggs. Delay setting small eggs (those more than 10% less than average
) for 8 to 16 hours.
7. Maintain correct
incubation temperature, humidity and ventilation. Make sure air intake does
not draw contaminated air into the incubator.
8. Turn hatching
incubator room temperature between 21 and 24BC with good ventilation and
relatively high humidity.
vaccinating and beak trimming equipment. Newly hatched chicks may pick up
contamination and infection in the hatchery from vaccinating and beak
trimming equipment. This equipment requires a very rigid sanitation schedule.
12. Practice strict
sanitation; cleanliness is very important for successful hatching operation.
Make sure belts, equipment and workers hands used to move eggs or newly
hatched chicks are kept clean.
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