Light
The sense of sight and the perception of light differ, in some respects considerably, between humans and turkeys. A key difference is that, in addition to the red, green and blue wavelength ranges, birds’ colour perception also includes the UV-A range.
Side note: This is due to the so-called cones in the retina of the eye; compared to humans, birds have an additional UV cone. If all four cones are stimulated (red, green, blue, UV), the turkey perceives ‘white light’; if a colour is missing from the light spectrum, this can consequently lead to what is known as false-colour vision. Unlike sunlight or natural light, most artificial light sources do not contain any UV component, meaning that, for poultry, one colour is naturally missing from the visual spectrum. If, due to the housing system, natural and artificial light are mixed, or if the turkey is exposed to both light sources within the housing system (Louisiana-style houses, outdoor climate areas), this can cause confusion, as, for example, objects and other birds may appear differently to the bird, depending on the light source and the spectrum provided.
Light plays a role not only in terms of the animals’ vision, but also influences their physiology and behaviour. The following factors, amongst others, are significant⁵:
Colour; the composition of light by wavelength, also known as the spectrum
Brightness; the light intensity with which the aviary is illuminated (illuminance)
Flicker; the frequency of the light, expressed in cycles per second
Lighting programme; the day/night rhythm, i.e. light and dark phases
The colour spectrum between rearing (imprinting) and fattening should be known or coordinated
Under artificial lighting, the colour spectrum should correspond as closely as possible to daylight (full spectrum always includes a UV component)
At least 20 lux measured at the animals’ eye level during the light phase; during the dark phase, a maximum of 0.5 lux
Flicker-free in accordance with the guidance note ‘Requirements for artificial lighting in poultry farms’. The flicker frequency should be above 160 Hz when artificial lighting is used in poultry farming⁶
- Natural day-night rhythm; twilight phases are recommended³ or mandatory depending on the marketing organisation
Deviating condition
Flickering light
Flickering light can be a source of stress for turkeys, increasing the risk of feather-pecking and self-mutilation. Lamps with flicker frequencies of 160 Hz or higher are suitable for lighting turkey rearing houses, provided they emit a light spectrum adapted to the turkeys’ perception.
Deviating condition
Sunspots / Light spots
Sunspots can be caused, for example, by holes in the coop’s cladding, blinds that do not close properly, or openings through which light can enter from outside.
As turkeys are very curious animals,
sunspots encourage the birds to engage in feather-pecking
the birds may suffer from bruising, skin damage or even suffocation as a result of crowding
Measures
Ensure the henhouse is properly sealed and identify and remove or cover any sources of potential sunspots or light spots
A great deal of research is currently being carried out in the field of lighting in particular, so new concepts and approaches are to be expected over the coming months and years. The aim is to prevent conspicuous pecking behaviour and to provide the animals with activity and rest zones, for example by creating different brightness levels within the barn.