Switching from blue to red lighting during the egg-laying cycle could affect bird immunity, according to new US research.
The study, led by scientists at Mississippi University, looked at how hens would react to a switch from blue light during the pullet phase and red light in the production phase. Laying hens need light to grow and to start producing eggs. However, advances in poultry science research and the availability of LED bulbs have proven that not all light is created equal.
In the past, researchers have shown that laying hens under red light not only started to lay eggs earlier but also had higher egg production than birds kept in white or green light. And multiple studies have linked shorter wavelengths of light, like blue light, to better growth and less activity in the hens.
The latest research found that birds housed under red lights had a relatively lower spleen percentage compared with the control group. This may indicate that the birds have weaker immune systems.
In the study, scientists raised 1,000 Hy-Line W-36 hens in a cage-free housing system consisting of 2 identical rooms. Hens in one room got blue light from 1-18 weeks of age. Those same hens then switched to red light from 19-31 weeks of age. The control group in the other room was exposed to normal-LED bulbs throughout the study. The researchers then repeated the experiment.
Switching from blue to red appeared to make a difference when it came to hen size and egg composition. The scientists found hens raised in blue light had a significantly higher body weight during the pullet phase. Once the lights turned red, hens produced eggs with a higher relative egg yolk percentage and a lower relative albumen (egg white) percentage, compared with hens given normal-LED light.
However, actual egg production numbers and several other factors didn’t appear to be influenced by the colour of light, the scientists wrote: “There was no difference between the light treatments with respect to hen day egg production, brain weight, tonic immobility and hormone concentration.”
The full paper, ‘The effect of blue and red LED light on the growth, egg production, egg quality, behaviour and hormone concentration of Hy-Line W-36 laying hens’, can be found in the Journal of Applied Poultry Research.