Canadian Poultry Magazine

Flickering lights studied for effects on turkey farms

By Jane Robinson   

Features Turkeys

Researcher investigates impact on poultry health and productivity, finding minor behavioural and performance changes.

April Hammond completed her Masters on this light flicker project with turkey hens, and now works as a research assistant in Karen Schwean-Lardner’s lab at the University of Saskatchewan. Photo: University of Saskatchewan Media Productions

If you’ve spent any time in a room with flickering lights, it might have triggered a reaction ranging from annoyance, fatigue to a splitting headache. When Karen Schwean-Lardner was invited to tour some Ontario turkey farms that were having light flicker problems, she got a migraine and an idea. 

Not much is known about the effect of light flicker on poultry, especially turkeys, and those barn visits left the University of Saskatchewan researcher wondering about the impact unstable lighting might be having on the birds. 

“There is very little information on the productivity or behaviour of birds raised with exposure to light flicker,” says Schwean-Lardner. “Some work has been done in laying hens and broilers, but the more work we do, the more we realize that turkeys don’t often respond the same way as broilers, and nobody had looked at light flicker in poults.”


Schwean-Lardner and graduate student April Hammond recently completed a project studying the effect of light flicker on turkey hens, looking at a wide range of measures related to performance, health and well being. Hammond’s work on the project earned her a Masters degree.

“We’re always trying to look at a big picture in our studies,” says Schwean-Lardner. “If we only looked at the effect of light flicker on bird behaviour, we’d be missing the effect on production, which is what producers really want to know about.”

Three flicker frequencies
Light flicker is visible when the frequency (hertz) of the transition between light and dark is slow enough to be seen. This type of flicker is common with artificial light sources, and can occur in barns where newer LED lights are used in incandescent sockets.  

Schwean-Lardner and Hammond evaluated three different light-flicker frequencies (30 Hz, 90 Hz and 195 Hz) in turkey hens raised from day old to 11 weeks. The researchers exposed the birds to the light flicker during daylight hours. 

The study used infrared cameras to monitor behavioural activity including stress and fear, and also gathered performance measures throughout for body weight, feed consumption and feed efficiency. 

“We were trying to mimic what would happen in barns, as much as possible, using purpose-built control boxes to deliver the different flicker frequencies,” says Schwean-Lardner.

The 30 Hz frequency flicker is visible to humans and turkeys. At 90 Hz, there is some indication light flicker may be visible to turkeys, but not to people. And the highest level tested – 195 Hz – is not visible to people or birds. “Turkeys have better vision than people with much wider peripheral visions for numerous reasons, including that light can penetrate through the skull,” says Schwean-Lardner.

Little effect on birds
Overall, flicker had minor effects on turkey hen behaviour, with many stress and fear responses unaffected by visible or non-visible (90Hz and 195 Hz) flicker. There were differences in behaviour when the birds were young, with 30 Hz reducing some comfort and exploring behaviour.

“We did notice that on the day the birds were placed in visible flicker, they tried to hide under the feeders to get away from it,” says Schwean-Lardner. “We weren’t able to measure this effect, be we could see the young birds were trying to avoid the flicker when they were first exposed to it.” 

When looking at bird performance, they found some lower body weights at the 30 Hz frequency at an early age. But as the birds grew, there were no overall changes in final body weight or feed efficiency between the birds. “We could not find differences overall, with body weight being equal despite the treatment,” says Schwean-Lardner.

All in, she expected to see bigger differences when birds were exposed to flicker. “I thought we would see significant reductions in body weight and significantly higher mortality, but the differences were not what we anticipated between the different levels of flicker frequency,” she says.

Worth the fix
Although the productivity impact on the turkey hens was not significantly different when they were exposed to varying levels of light flicker, Schwean-Lardner says it’s always better to fix the flicker as it is known to impact anyone working in barns. 

“I think producers should know that in the 90 Hz range, we did see higher levels of aggression so flicker may have some negative effects on birds, even if we can’t see it,” says Schwean-Lardner. “So, if you go into a barn and don’t see flicker, it might still be there and might be impacting the birds.” An oscilloscope can be used to measure non-visible light flicker.

Then there’s the additive effects of stressors for birds in the barn. Flicker is a stressor that can be corrected, and doing that will likely mean those birds are able to withstand other stressors a little bit better.

Schwean-Lardner wants to do more work in this area, but admits it was really tough conditions for the whole team to work under. “Working under flickering lights on this project meant it was much tougher to see birds that needed to be culled,” she says. “And culling is one of the most important animal welfare things we can do.”

She’d also like to be able to do brain MRIs on birds to see what was going on under flicker, and also repeat the work in turkey toms as their behaviour is different from hens. “Toms spend longer in the barn so we might see very different results.” 

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