Optimizing poultry health and performance requires navigating a wide range of variables, including chick quality, nutrition, biosecurity and management of the poultry house environment.
“At the end of the day, we try to provide an optimal environment for birds so that energy from their food and water goes toward growth and development,” said Brian Fairchild, PhD, professor and extension poultry specialist at the University of Georgia. And lighting in the houses plays an important role.
In his presentation, “Rethinking light programs during brooding,” from the Canadian Poultry’s Broiler School webinar series, Fairchild explained that energy is used in three ways: growth and development, maintenance, and to overcome stressors. Bird activity increases with light intensity and birds eat and drink when the lights are on. But Fairchild noted, “Raising poultry isn’t all about growth, even in the first 7 to 10 days.”
Giving birds time to mature and develop strong skeletal, digestive, thermoregulation and immune systems is just as important and, possibly, more important than prioritizing growth during the first week, he explained.
However, lighting not only influences birds’ behavior but also affects their physiology. Additionally, lighting is even more complex because the hours of light, as well as intensity and spectrum, impact poultry.
“It’s not all about what the eyes can see,” Fairchild pointed out. For example, red and orange light between 2,700 and 3,000 Kelvin has longer wavelengths that penetrate birds’ feathers, skin and skull, stimulating the extra-retinal receptors, which research has shown to promote sexual development.
Day length influences poultry’s daily rhythms, hormonal concentrations, reproduction and immune system. “In near continuous or continuous light, stress hormones and plasma corticosteroids increase, and melatonin decreases.”
Dark period’s importance
Fairchild’s research has highlighted the importance of a continuous dark period of 4 to 6 hours, which interestingly coincides with peak melatonin production. Melatonin, although not often discussed, plays a key role in behavior, thermoregulation and the health of the cardiovascular, excretory, immune and reproductive systems.
Typically, chicks are introduced into poultry houses that are illuminated continuously for the first 7 to 10 days. Although this method encourages bird activity and may contribute to chicks finding food and water sources, it doesn’t necessarily lead to heavier birds at harvest.
Fairchild found that birds exposed to a dark period from day 1 were slightly behind control birds in weight at 7 days of age but they quickly caught up by 10 days of age. In pen trials, birds actually weighed more at 10 days through 5 weeks of age. “Older birds, around 48 days old, didn’t exhibit a weight difference when housed with between 17 and 20 hours of light, but they didn’t perform as well in environments with continuous light,” he stated.
“Based on research conducted in Canada, the feed-conversation sweet spot is about 20 hours of light and 4 hours of darkness,” he said. However, for birds raised to 7-9 weeks of age, 6 hours of darkness has been shown to be similar in performance to 4 hours of darkness.
Fairchild prefers uniform lighting in houses during brooding and wants to see birds distributed evenly. He also likes to see birds up and moving when the lights are on, but said light intensity doesn’t impact performance once the birds locate food and water resources, depending on the design of the light system. Specifically, he noted that lowering light intensity to 5 lux doesn’t have a negative impact on bird performance.
Water consumption to monitor lighting
It is well documented that consumption rises when lights turn on, then occurs at a steady rate throughout the day and increases again before the lights turn off.
Because feed consumption is directly linked to water consumption but can be difficult to measure, the UGA Poultry Housing lab uses water consumption to monitor house lighting. He suggested using at least two water meters, one at the front of the house and one at the back, to alert producers to lighting inconsistencies.
For example, in one study, the birds on one farm were drinking more water at the back of the house. This inconsistency was due to the birds responding to light coming in through the fans lining the back wall. Adjusting the lighting to make it more consistent throughout the house remedied the situation and resulted in a more uniform flock.
Continuous lighting impacts
“Continuous lighting may have a negative impact on poultry health,” Fairchild said.
In another study, birds from day 1 housed in continuous light were compared to birds housed with 6 hours of continuous darkness. All the houses in this study experienced deaths related to inclusion body hepatitis. However, in houses with the dark period, there were fewer lame birds, less mortality and no significant difference in weight gain or feed conversion.
“Although several factors may have come together to result in healthier birds, it is interesting that birds with higher melatonin levels experienced less lameness and mortality,” Fairchild commented.
He prefers lighting changes to be instantaneous rather than adjusted gradually over multiple days. “Any lighting changes will require a 2- to 3-day period for the birds to adjust to a new schedule.
A dark period from placement may lead to better health
“Research has shown no downside to incorporating a dark period from day 1, but increased stress levels with continuous light have been documented,” Fairchild commented. Although it may not be observed in every flock, a dark period could lead to improvements in overall bird health. He believes that producers willing to experiment with an alternative to continuous lighting of houses for the first several days might see advantages.
“Producers should think about the potential benefits of offering birds a dark period starting on the day of placement,” Fairchild noted.
