Measurements of light in poultry houses and assessment of illuminants have until now been based on parameters developed for human perception of light.
But bird eyes generally differ considerably from human eyes, especially within spectral sensitivity and their ability to resolve temporally varying stimuli.
Past research has shown that light plays a critical role in the development of feather pecking and cannibalism. Photo: Mark Pasveer
Scientists in the working group Applied Poultry Sciences say the differences in the anatomy and physiology of human and avian eyes should be taken into account in order to optimise the lighting in poultry houses.
Light plays critical role in poultry development
Past research has shown that light plays a critical role in the development of feather pecking and cannibalism.
UV-A light needs to be considered
In their abstract of a paper published in the latest Lohmann Tierzucht global newsletter, researchers led by Dr R. Anderson said suitable illuminants should cover the whole spectrum contributing to the reception of light, including UV-A light.
The light colour (Kelvin) appears to be inadequate for the assessment of the spectrum, because it only reflects the wave length with maximal intensity.
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Spectral data can be compared with reference values for chickens and turkeys, based on their natural habitats. The emitted light frequency should be at least 120 Hz.
A generous additional safety margin is highly recommended because individuals may vary in their flicker fusion frequency.
More research still needed
The comparison of different illuminants offered for poultry houses indicate a need for more research and development to improve the light quality in poultry houses.
Development of procedures to test light intensity
And procedures for testing light intensity must be developed which will show the brightness perceived by commercial poultry.
Light intensity in poultry houses are commonly measured with lux meters, which cannot detect UV-A light, even though these ultraviolet wavelengths contribute to brightness perception in birds. Birds are therefore likely to see their environment brighter than the measurement suggests.
As a practical approach, tests of light intensity in functional areas of non-cage systems (eg feeder and rest area) are recommended, corresponding to varying preferences for different functions.