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The importance of light and lux to reproduction

by 5m Editor
23 April 2007, at 12:00am

By Hybro B.V. Light is extremely important for chickens. And not only to see and find food, water or a nest.

The chicken’s reproductive system is triggered by light – and to understand how it works, we have to understand the relationship between light and the birds.

What is light?

Light is a form of electromagnetic radiation, like radiowaves or rontgen waves, for example. Wavelengths in the region of 300 - 800 nm (1 nm = one millionth of a millimeter) can be seen by the human eye as light. The wavelength determines the colour of light, from violet light at c.300 nm, ascending through blue, green, yellow and orange, to the longest visible wavelength of 800nm: red light. White light is the visual effect of combining all colours. Predominantly red/orange coloured light is typically considered ‘warm’ (Candle light), while from bright white to a blue/green hue seems cold and hard.

The intensity of light, wherever it occurs in the spectrum, is measured in ‘lux’: the amount of electromagnetic radiation received per surface area. Lux is measured irrespective of whether electromagnetic radiation is in the wavelength of blue or red colour. It is purely a measure of the amount of radiation.

Chickens and light

The chicken’s reproductive system is not so much influenced by the light they see, but rather by the light received in the brain. The brain of a chicken contains light-sensitive cells, which are known to trigger the reproductive system. These are not so much stimulated by light received through the eye, but rather through the skull.

Warm light (long wavelengths) is most effective at penetrating to the brain. Compare it with music, where the bass (long wavelengths) can be heard easily outside a house or car. Chickens use bright light (short wavelength, high amount of blue/green) to see, but they need red light (long wavelength) for reproduction.

To use light effectively in chicken houses:

  • Measure the amount of lux using a luxmeter. The house may well be light enough. But if that light is very bright and there is only a small amount of red colour in it, the birds’ may not be sufficiently stimulated to reproduce.

  • Although ‘red’ (long wavelength)lamps may not seem very bright to us, the actual lux reading can be suprisingly high. White bright light will seem more intense, but there can in fact be less lux.

  • As birds respond to the red wavelengths, white bright light is less effective for reproduction. If we try to provide enough red light with this light source, the increase in total light intensity risks over-stimulating the birds’ behaviour, resulting in nervousness, stress and pecking.

  • Because chickens use short wavelength light to see, using predominantly red light may lead to an increase in floor eggs.

  • In rearing, common light bulbs (warm, yellow/orange light) are often used because they can be dimmed easily. When these birds are transferred to a black-out production house with bright white TL light, total light may increase. But if the amount of red light either decreases or does not increase significantly, the birds' reproductive behaviour is unlikely to be triggered effectively.

To avoid problems, we must:

  • Look not only at lux (light intensity), but also at the colour of the light

  • Ensure that breeders step up especially in the red light fraction coming into production

  • Make sure breeders in production get enough “warm” light with a high amount of red colour
April 2007