It is the season for flickering lights and turkeys — just avoid mixing the two during live production, and not just in a spirit of humanity.
That might be inferred from research by University of Saskatchewan scientists, who found that lights operating with a visible flicker can cause turkey hens to eat less, gain less weight and even die in greater numbers during rearing.
Over 11 weeks, the team tested three light frequencies (30, 90, and 195 Hertz) in controlled rooms housing the hens, which they randomly allocated to treatments. They measured a range of indicators: body weight, feed consumption and efficiency, mortality flock uniformity, feather condition and cleanliness, footpad score, mobility litter quality and ocular weight and dimensions.
Light matters
Overall mortality was highest in the 30Hz group compared to birds in the 195 Hz frequency lighting rooms. At eight weeks, body weight was also lower for birds in the 30Hz group than under the 195 Hz treatment. However, they saw no other weight differences during periods of the work.
Birds ate less food in the 30Hz group over the first eight weeks than the other two groups, but in the latter stages of the study, when corrected for mortality, turkeys under 30Hz lighting had improved feed conversion.
While the effects on body weight, feed efficiency and mortality were statistically significant, they observed that birds appear to adapt to light conditions and compensate later on in production.
“The increase in overall mortality demonstrates that visible flicker could be detrimental to production and bird well-being,” the researchers wrote in the journal Poultry Science.
“The mortality of turkey hens could be reduced under light-flicker frequencies past the point of unconscious perception compared to visible light flicker,” they added, with the 195 Hz treatment in the study meeting this requirement.
Flicker changes eyes, lesions and behaviours
As well as the production impacts, light flicker also had an impact on birds’ eyes, they found. Birds under the lowest frequency light had higher recorded eye sizes across two dimensions, compared to birds raised under higher frequencies. They saw higher occurrence of footpad lesions and poorer feather condition both at the highest and lowest frequency lighting conditions, which they stressed was “not well understood” and had “no clear cause.” There were no impacts of light flicker on litter quality.
They also saw light flicker particularly affect turkey hens in early life in further work, published in the same journal, which explored behavioural effects of different light frequencies. In this strand of study, they saw that visible light flicker had some minor negative effects on behaviours related to bird comfort and exploration, with preening effects continuing into adulthood.
