Laying hens in caged housing have favourable responses to artificial lighting. As producers shift from conventional cages to aviaries, enhanced colonies, and free-range systems, enquiries regarding lighting have emerged. What is the significance of lighting for poultry? What criteria do you use to select appropriate lighting for each system? Dr Ian Rubinoff, European account manager and technical services veterinarian at Hy-Line International, and Karen Schwean-Lardner, professor in the Department of Animal and Poultry Science at the University of Saskatchewan, impart their experience.
What is the significance of lighting for poultry?
To comprehend the significance of lighting in chicken production, it is essential to examine the birds' biological composition. In humans, light enters the brain via the eyes. In chickens, light enters not just through the eyes but also through the cranial apex via the pineal gland and the adjacent pituitary gland near the hypothalamus. While humans possess only three types of cones-specialized photoreceptor cells that facilitate the perception of red, blue, and green light-chickens have four varieties: red, blue, green, and ultraviolet cones.
Similar to humans, the lives of poultry are governed by a consistent diurnal cycle. When birds maintain an appropriate circadian rhythm, they establish normal daily patterns of behaviour throughout daylight hours. This is crucial for processes such as melatonin synthesis. "This normal cycle is crucial for birds as it influences immune function, growth rate, and reproductive hormones," elucidates Schwean-Lardner. "Providing a day-and-night cycle enhances avian health, boosts immune function, increases mobility, and heightens alertness."
"Birds exhibit increased activity in accordance with a diurnal cycle," she continues. "They will indeed exhibit improved growth, which is quite intriguing and contrary to the prevailing beliefs a decade ago."
Schwean-Lardner is presently investigating the significance of circadian rhythms in avian species. She is examining aspects such the appropriate age for initiating lighting programs, the methodology for implementing such changes, and the effects of abrupt vs gradual alterations in lighting regulation on chickens. Her primary focus is on diurnal cycles. "In my opinion, birds require darkness," stated Schwean-Lardner. The amount will be contingent upon several factors.
Poultry researchers focus on three parts of the spectrum that potentially influence avian behaviour: ultraviolet light, visible light, and infrared light. Ultraviolet light occupies the shorter wavelengths of the spectrum. The wavelength of visible light spans from 400 nanometres (nm) to approximately 700 nm. The wavelength of infrared light exceeds that of visible light, measuring over 700 nm. Humans perceive light within the spectrum of 400–750 nm, whereas hens perceive light within the spectrum of 315–750 nm. Furthermore, hens possess the ability to perceive elevated wavelengths in the spectrum of around 480 and 630 nm, according to Rubinoff.
Rubinoff elucidated during a presentation at the International Egg Commission's Global Leadership Conference in Bruges earlier this month that a standard LED spectrometer, an instrument that quantifies light intensity across various wavelengths, enables measurement of light in four distinct modalities. Correlated Colour Temperature (CCT) is quantified in Kelvin (K). "This serves as an excellent preliminary gauge for determining whether a light is warm or cool," Rubinoff elucidated. "A colour temperature below 3,000K signifies warm light, whereas a temperature above 4,000K indicates cool light."
"This does not provide any indication regarding the quality or composition of the light, but it offers a preliminary calculation," he stated.
Abbreviated as 'colour-rendering index', CRI is a number ranging from zero to 100 percent that indicates the fidelity of a light source in reproducing colour relative to a reference light source.
Light is quantified in lux, the standard unit for illuminance, which denotes the quantity of light incident on a surface per unit area. "It is essential to note that lux is quantified at a specific spatial point," stated Rubinoff. The light intensity I measure here differs significantly from what I measure below. A modification of merely 10 cm can significantly alter your lux and light intensity.
"This is a concept that poses significant challenges for us, particularly as humans, to comprehend," he continued.
The final measurement is the peak wavelength, which denotes the predominant colour among all wavelengths emitted by a specific light source.
The application of lighting in various contexts
On a typical bright day, light intensity can reach up to 150,000 lux, indicating that hens with outside access are subjected to a significantly high level of light intensity. As the sky becomes overcast, a portion of the red spectrum of sunshine is covered, resulting in a predominance of the blue spectrum. During sunset or sunrise, we observe the contrary phenomenon. There is an augmentation in the red spectrum and a diminution in the blue spectrum.
Rubinoff elucidated that incandescent light resembles a small fire contained within a glass sphere. Incandescent bulbs offer an optimal spectrum for laying hens. Regrettably, they exhibit significant inefficiency, prompting producers to transition to alternative light sources, beginning with fluorescent bulbs.
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