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Broiler Heat Stress And More Light At Night
Extended lighting periods help
boost welfare and production of big broilers during high seasonal temperatures,
a University of Georgia study showed.
Research in six commercial
poultry barns looking at air temperature, velocity, relative humidity and
deep-body temperature in broilers revealed an interesting multi-factorial
process, Brian Fairchild, PhD, poultry extension scientist, told Poultry
Health Today.
The studies conducted by
Fairchild and Mike Czarick, extension specialist, placed small heat sensors
inside the body cavity of broilers 2 weeks before catch during the summer
months.
“We were looking at deep-body
temperature during the hottest months of the year on the biggest birds,
definitely a stressful time for those birds,” Fairchild explained. During this time period, they ran fans
continuously to eliminate air speed as a variable.
What they
discovered was the birds’ temperature actually increased during the night when
the outdoor temperatures cooled. “This is
opposite what research shows happens in rats and humans,” he said.
They found that lighting - or
lack thereof - played a major role in this nighttime increase in body
temperature.
“The lights go off at dusk, the
birds sit down and their litter is like a warm blanket,” Czarick said. “When sitting, a bird also decreases its
surface area available for cooling by air movement.”
Another important component of
the dark period is the birds’ feeding habits.
“The birds are going to eat the
same amount of feed per day, so if you extend the lighting period, they have
more time to eat, spreading out the digestive process which also produces
heat,” Fairchild
said.
If lights are turned off at dusk,
the birds stop eating and go to resting until the lights come on again.
As soon as the lights go back on,
the birds begin eating and drinking heavily, causing the birds’ core
temperature to rise during the day as well.
“The longer the dark period, the
higher the differential in body temperature,” he said.
According to Czarick, growers
concentrate too much on bird temperature during the day.
“The key is how much the light
program affects bird temperature during the night. It really comes down to bird
behavior.”
“A couple more hours of power
usage is not significant,” he added, pointing to today’s low-energy LED bulbs. “But leaving the lights on until midnight or
1 am does have a large impact on bird comfort and welfare.”
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