Environmental Factors to Control When Brooding Chicks
Brian Fairchild, Extension Poultry Scientist with the University of Georgia, discusses temperature and chick physiology, the effects of temperature and chick performance, the importance of relative humidity, ventilation and lighting as well as energy conservation.The main objective in brooding chicks is efficiently and economically to provide a comfortable, healthy environment for growing birds. Temperature, air quality, humidity and light are critical factors to consider. Failure to provide the adequate environment during the brooding period will reduce profitability because of reduced growth and development, poorer feed conversion, and increased disease, condemnation and mortality.

Temperature and Chick Physiology
Maintaining the correct temperature is critical in chick
brooding, especially during the first two weeks of the
chick’s life. Early in life, the chick is poorly equipped to
regulate its metabolic processes to adequately control
its body temperature. As a result, the young chick is
dependent on environmental temperature to maintain
optimal body temperature. If the room temperature
decreases, the chick’s body temperature will decrease.
Likewise, if room temperature increases, the chick’s
body temperature will increase.
Chilling or overheating
during this crucial period can result in poor
growth, feed conversion and increased susceptibility to
disease. Proper brooding practices must maintain the
chick’s body temperature so that it does not have to use
energy to lose heat by panting or generate heat through
metabolism.
Research has shown that the chick develops the ability
to regulate its body temperature around 12 to 14 days
of age. The chick can be easily stressed if its body temperature
decreases or increases by as much as one degree.
Once the body temperature changes the bird will
try to compensate and in most cases this means that it
will have a negative effect on performance. The body
temperature of a day-old chick is about 103°F (39°C),
but by about five days of age body temperature is 106°F
(41.1°C), the same as the adult.
Extreme temperatures
(high or low) often result in chick mortality, but even
mild chilling or overheating can affect the performance
of young chicks without causing death. While chicks
are more tolerant of high temperatures than adult
birds, high temperatures for extended periods of time
increase mortality and have negative impact on performance.
Research has shown that chicks that are subjected to
cold temperature have impaired immune and digestive
systems. As a result, cold stressed chicks have reduced
growth and increased susceptibility to diseases. Cold
stressed chicks will exhibit higher incidence of ascites,
a metabolic disorder that results in reduced performance,
increased mortality and increased condemnations
at the processing plant.
In research studies
where groups of chicks were brooded at either 80°F
or 90°F, the chicks reared under the warmer temperature
had better weight gains, feed conversion and
livability. Chicks brooded under 80°F experienced
slower growth than the high brooding temperature
treatment. The chicks reared under those
temperatures did not catch up in body weight and as a
result, weighed less at market age than birds that were
brooded properly. Not only do chicks exposed to low
brooding temperatures have reduce growth rates, they will also consume more feed to keep themselves warm,
reducing feed efficiency and increasing feed costs.
Temperature and Chick Performance
One of the goals during brooding is to maintain chicks
within their comfort zone, which is where they are
not using energy to gain or lose heat to maintain body
temperature.
When birds are kept in environmental
temperatures above or below their comfort zone, more
energy must be expended to maintain body temperature.
This extra energy will ultimately be supplied by
the feed consumed. Therefore, the energy from the
feed will be used to maintain body temperature instead
of growth and development resulting in poorer feed
conversion. Thus, the environmental temperature plays
a major role in determining the cost of producing a
pound of meat or a started pullet.
Proper brooding not only consists of maintaining
proper temperature but also the use of good husbandry
practices. Brooding temperatures will vary depending
on whether the heat source is air furnace, conventional
brooder or radiant brooder (Table 1). Note that the
temperatures in Table 1 refer to air temperatures that
are designed to provide a 90°F (32°C) floor temperature.
When brooding chicks, floor temperature is crucial.
Research suggests that average floor temperature
should be 90°F (32°C) on the day that chicks are placed
in the house. Forced air furnaces require higher temperature
settings because they heat the air which heats
the floor. A conventional pancake brooder directs
approximately 40 per cent of its heat to the floor and
60 per cent to the air. Radiant brooders project approximately
90 per cent of their heat to the floor and 10
per cent to the air. Because pancake and radiant brooders
direct more heat to the floor, the air temperature
required to get the desired floor temperature is less
than that required for forced air furnaces.
Table 1. Recommended air temperatures during brooding for broilers by heat source1 | |||
Air Temperature | |||
---|---|---|---|
Day | Forced Air Furnace2 | Conventional Brooder3 | Radiant Brooder4 |
0 | 93°F (34°C) | 90°F (32°C) | 88°F (31°C) |
3 | 90°F (32°C) | 88°F (31°C) | 86°F (30°C) |
7 | 87°F (31°C) | 86°F (30°C) | 84°F (29°C) |
14 | 83°F (28°C) | 85°F (29°C) | 82°F (28°C) |
21 | 78°F (26°C) | 80°F (27°C) | 77°F (25°C) |
1Temperatures based on those used currently by broiler companies
2Measured at chick height. 3Measured at chick height, one foot from edge of brooder canopy. 4Measured at chick height, four feet from edge of brooder canopy. |
Broiler houses are specifically designed to allow the environment directly around the chick to be closely controlled. In commercial broiler growing operations, broiler houses are insulated and equipped with mechanical ventilation systems to maintain house temperatures within five degrees F of the desired temperature regardless of outside temperature. Optimum chick brooding temperatures have been developed through many years of research and field experience.

The best method to monitor chick comfort is to observe
chick behaviour and regulate the temperature
accordingly. When observing a broiler house, chicks
should be distributed evenly across the house.
Chicks that are cool can be seen huddling together
(even next to the side wall) and will tend to sit in
feeder pans. Chicks that are hot will move away from
the brooders and furnaces, will pant and will stretch
out on the litter in efforts to cool themselves. Many
houses have environmental controllers that monitor
house temperature and turn brooders and furnaces on
and off as needed. The controllers also monitor the
amount of time a heat source operates. This information
can be used to locate areas of the chick environment
that might experience excessive air leaks or
drafts. For example, if the brooders/furnaces near the
tunnel curtain have more run–time than others in the
house, it may indicate air leaks around the curtain or
end wall door.
Relative Humidity
The ability of air to hold moisture depends upon its
temperature. Warm air can hold more moisture than
cold air. The term relative humidity refers to the percent
of water saturation of air at any given temperature.
The level of humidity influences the ability of the bird
to cool itself through panting and influences ammonia
production.
It is recommended that relative humidity be maintained
between 50 to 70 per cent throughout the growout
period, including the brooding period. Ammonia production
occurs due to the microbiological breakdown
of faecal material in the litter. Dusty conditions in the
poultry house are associated with relative humidity
below 50 per cent.
Relative humidity of 70 per cent or
greater provides environmental conditions suitable for
microbial growth in the litter. As the microbial population
increases, more ammonia is generated from
nitrogen sources found in bird faecal material.
Ammonia
is a gas that has a negative impact on bird health
and performance. Research shows that increased
ammonia impairs the immune system and increases
respiratory disease in birds. High ammonia levels during
brooding reduces growth rate, which is not gained
back during the remainder of the grow–out. Ammonia
production can be reduced through the control of relative
humidity which in turn is regulated by ventilation.
Managing the poultry house ventilation rates to keep
relative humidity between 50 and 70 per cent is recommended
to minimise ammonia production and dust.

(Miles et al., 2004)
Ventilation
Ventilation is needed to regulate temperature and remove
carbon dioxide, ammonia, other gases, moisture,
dust and odours.
Fresh air must be introduced uniformly,
mixed well with house air, and circulated properly
throughout the house. The flow pattern within the
building is very important. Air movement into the
house is accomplished via negative pressure. Fans
remove air from the house creating a negative pressure.
Air enters through inlets located in the walls or ceiling
and is directed across the ceiling to mix the air.


This allows the air to warm up to brooding temperature before coming into contact with the chicks. This also increases the moisture holding capacity of the air so that when the warm air does fall down to chick level it will pick up and hold more moisture from the litter helping to maintain litter conditions in the house.
Mixing of the incoming outside air and the inside air
prevents the cooler air from settling near the litter
and chilling the birds. Inlet openings and air speed
coming through the inlet is important in ensuring
that air moves along the ceiling. If the inlet opens too much or if the speed of the air entering through the
inlet is too low then the cool air will fall to the floor
more quickly. Not only with this cause a problem of
bird chilling, but can create cool spots on the walls
and floor. As warm air contacts these cooler spots
condensation will form creating wet spots. These wet
spots can lead to increase litter caking as well as more
ammonia production.
Circulation fans should be used to break up temperature
stratification and provide a more uniform temperature
throughout the poultry house. Moving the
warmer air to bird level not only helps maintain bird
body and floor temperatures, but also helps remove
moisture from the litter.
Fan operation is controlled by temperature to maintain
the desired temperature. Some fans are operated by a
timer to regulate relative humidity and maintain good
air quality when the house is at the desired temperature.
The house environmental controller operates
the fans based on temperature and timer settings. The
controllers will open air inlets located in the side walls
or ceiling to ensure uniform air entry into the house.
The amount the inlets open is determined by static
pressure.
Lighting during Brooding
Light is an important factor during brooding that
should not be ignored. Chick activity is greater in
bright light intensity than in low light intensity.
During brooding, the light should be at the brightest intensity
to encourage chick activity thus assisting them to
locate feed and water. Once they learn where feed and
water are located (somewhere around seven to 10 days of
age), the light intensity and duration can and should be
reduced. Light systems should be designed to produce
a minimum of 25 lux (2.5 foot candles) or more at
bird level. Many broiler houses being built today are
capable of provide up to 40 lux (4 foot candles) at chick
level in the brood area.

Using the air allows higher ventilation rates to be used without increasing fuel usage. These increased ventilation rates will help maintain relative humidity between 50 and 70 per cent.
The light system design should allow light intensity
and duration to be modified as the birds age and provide
a uniform light intensity at bird level. Typically,
the lights are operated 23 hours a day during brooding
and the light intensity is at maximum. Between seven and
10 days of age, the number of hours the lights are operated
should be reduced (depending on the operation’s
guidelines) and by 10 to 14 days of age, the light intensity
should be reduced to 5 lux (0.5 foot candles).
The
main purpose of the lighting during the brooding is
to ensure that chicks are active and that they seek out
food and water sources.
Energy Conservation
- Make sure that controller sensors/thermostats are
placed properly – Positioning sensors/thermostats too close to a
brooder or too close to the chicks or too high off
the ground may result in bird chilling. Positioning
them in too close to the side wall, brood curtain or
where air is entering the house may result in excessive
fuel usage.
- Use circulation or paddle fans – The use of these fans will move warm air off the
ceiling eliminating temperature stratification and
get heat down to chick level where it is needed and
reduce heating costs. Studies show that circulation
fans are effective no matter which type of heating
system is being used.
- Use attic inlets – Pulling air from the attic on cool days when the
sun is out can result in higher ventilation rates
without increased fuel costs. This allows producers
to take advantage of the warmer air found in the
attics that will help to maintain relative humidity
between 50 and 70 per cent. To operate attic inlets
properly, the house must be tight enough to pull at
least 0.13 inches of water column in a static pressure
test. If the houses cannot pull this static pressure,
efforts should be made to tighten the houses
to reduce leakage before installing attic inlets.
- Eliminate leakage – Sealing up leaks provides control of where and how
much air will enter the house. This will ensure that
the air comes in through planned inlets and will
minimize bird chilling, litter caking and temperature
stratification during cold weather.
- Use five–minute timers instead of 10–minute timers – This will reduce house temperature drops resulting
in less heater run time and will help regulate ammonia
and moisture levels.
- Clean and repair brooders on a regular basis – Proper brooder maintenance will reduce carbon monoxide and will burn fuel more efficiently. Brooders should have the dust blown off in between each flock. Keep the burner orifices clean. Use the proper size reaming needle to avoid altering the orifice size and wasting fuel.
References
Carlile, F.S., 1984. Ammonia in poultry houses: a literature
review. World’s Poultry Sci. J. 40:99-113.
Czarick, M., 2001. Circulation fans in houses with radiant brooders. January. University of Georgia Cooperative Extension.
Czarick, M. and B.D. Fairchild, 2004. Leakage and litter caking. Poultry Housing Tips. November. University of Georgia Cooperative Extension.
Czarick, M. and B.D. Fairchild, 2003. 1/15 h.p. circulation fans. Poultry Housing Tips. November. University of Georgia Cooperative Extension.
Czarick, M. and B.D. Fairchild, 2001. Environmental controller temperature sensor placement. Poultry Housing Tips. November. University of Georgia Cooperative Extension.
Czarick, M. and M.P. Lacy, 2000. The importance of proper inlet adjustments. November. University of Georgia Cooperative Extension.
Czarick, M. and M.P. Lacy, 2000. Heating system thermostat/sensor location. November. University of Georgia Cooperative Extension.
May, J.D. and B.D. Lott, 2001. Relating weight gain
and feed:gain of male and female broilers to rearing
temperature. Poultry Sci. 80:581-584.
Miles, D.M., S.L. Branton and B.D. Lott, 2004. Atmospheric
ammonia is detrimental to the performance
of modern commercial broilers. Poultry Sci. 83:1650-1654.