“This is something that is very difficult for us, especially as humans, to understand,” he continued. A change in even as little as 10cm can change your lux and light intensity by quite a bit.” “What I measure here for light intensity is very different than what I measure down here. “It is important to remember that lux is measured at a point of space,” said Rubinoff. Light is also measured in lux, the standard unit for illuminance, or the amount of light striking a surface over a given area. Short for ‘colour-rendering index’, CRI is a scale from zero to 100 per cent that expresses how accurate a given light source is at rendering colour when compared to a reference light source. “This doesn’t give any indication as to the quality or composition of the light, but it gives a rough calculation,” he said. “Under 3,000K gives an indication that it’s a warm light, and above 4,000K gives an indication that it is a cool light.” “This is a great rough indicator for telling if a light is warm or cool,” Rubinoff explained. We have CCT or ‘correlated colour temperature’, which is measured in Kelvin (K). Using a standard LED spectrometer – an instrument that measures the intensity of light at different wavelengths – we can have the ability to measure light in four different ways, Rubinoff explained during a talk at the International Egg Commission’s Global Leadership Conference in Bruges earlier this month. Additionally, chickens can see higher peaks at the spectrums of around 480 and 630 nm, said Rubinoff. While humans can see in the range of 400–750 nm, chickens can see in the range of 315–750 nm. Infrared light’s wavelength is longer than the light we can see, measuring above 700 nm. The wavelength of visible light ranges from 400 nanometres (nm) to around 700 nm. Ultraviolet light is towards the short end of the spectrum. Poultry researchers are interested in three segments of the spectrum, each of which can have an effect on birds’ behaviour: ultraviolet light, visible light and infrared light.
“How much will depend on a number of things.” “Birds have to have darkness in my opinion,” said Schwean-Lardner. Her main area of interest, though, is day-night cycles. She’s looking at factors such as the age at which lighting programmes should start, how that change should be made and how abrupt versus gradual changes in lighting regulation impacts poultry. Schwean-Lardner is currently conducting research on the importance of day-night cycles in birds. “They’ll actually grow better, which is really interesting and the total opposite of what was thought ten years ago.” “Birds tend to be more active when they have a day-night cycle,” she continues. “By giving that day-and-night cycle, you improve the health of the birds, you improve the immune status, you improve mobility and you improve alertness.” “It is a normal cycle that is so important for birds because it drives things like immune function and growth rate and reproductive hormones,” explains Schwean-Lardner. This is important for functions like melatonin production.
When birds have a proper day and night cycle, they develop the proper diurnal rhythms – that is, a routine of typical activities during the day. Like humans, poultry’s lives revolve around a regular day-and-night cycle.
Whereas in our eyes we have just three types of cones – specialised photoreceptor cells that are responsible for our perception of red, blue and green light – chickens have four: red, blue and green cones, as well as a cone for ultraviolet light. In chickens, light penetrates not only through the eyes, but also through the top of the skull, via the pineal gland, and through the pituitary gland next to the hypothalamus. In humans, light reaches the brain through the eyes. In understanding why lighting is important in poultry production, it’s necessary to look at the birds’ biological make-up. Why is lighting important for poultry? And how do you choose the right lighting for each system? Two poultry specialists, Dr Ian Rubinoff, European account manager and technical services veterinarian at Hy-Line International, and Karen Schwean-Lardner, professor at the University of Saskatchewan in the department of animal and poultry science, share their expertise. But as producers transition from traditional cages to aviaries, enriched colonies and free-range systems, questions about lighting have surfaced. In caged housing, laying hens respond well to artificial lighting.
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