Birds depend on increasing day length as a signal to mature sexually, which means that controlling and manipulating photoperiod is critical to optimize reproduction in poultry. The type and quality of light used also is very important, with broad-spectrum lighting traditionally being used to successfully control reproduction.
GETTING THE LIGHT RIGHT
Conventional artificial light sources such as incandescent lighting provide a broad spectrum and have been extensively used by the poultry industry very successfully. However, incandescent lighting is the least efficient of any existing light source and its sale is to be phased out. This means that new, more efficient lighting sources need to be used – but these also need to be well researched to ensure the future prosperity of the poultry industry.
The spectrum provided by a lighting source not only looks different to the eye, but also affects bird physiology differently. Previous research has shown that light in the red end of the spectrum can penetrate the skull and directly stimulate the reproductive axis, while lower wavelengths from the blue/green end of the spectrum may be inhibitory to reproduction. Therefore, it may be possible to use a lighting system that is extremely efficient but using only part of the light spectrum to achieve the desired outcome.
Dr. Grégoy Bédécarrats’ research program at the University of Guelph is focused on light-emitting diodes (LEDs), which can be adjusted to produce any spectrum under unlimited luminance settings with minimal energy input. As such, this technology represents the best option for energy friendly, sustainable poultry farming in Ontario. Bédécarrats was interested in the effect of light wavelength on laying hens in order to design a novel LED lighting system to promote egg-laying without negatively impacting health and welfare.
Computer controlled LED light fixtures were mounted on top of conventional cages and the research barn was divided into three sections where hens were exposed to either pure green, white or pure red wavelengths. To determine whether any effect was mediated via the retina of the eye, a blind line of Smoky Joe chickens (containing both blind and temporarily sighted hens) was used. As the egg-laying industry progressively transitions toward colony-enriched cages and aviary systems, the research team also tested the effect of light wavelength on commercial layers housed in collective floor pens. Data was collected on their behaviour and social interactions (such as activity and aggressiveness), as well as on production levels.
The team’s findings showed that red light promoted an early, strong stimulation of the reproductive axis with a longer and higher peak production, while green light resulted in delayed sexual maturation. Since the researchers observed no difference between blind and sighted hens, they concluded that the retina of the eye does not appear to be involved in mediating the effect of light on reproduction.
Results also show that, unlike the line of Smoky Joe Leghorn (which has not been selected for egg production), commercial layers spontaneously matured prior to photostimulation, and as a result, light wavelength did not impact age at first egg or peak production.
RED LIGHT, GREEN LIGHT
Nonetheless, red light was once again superior in stimulating the production of sex hormones. Interestingly, green light promoted utilization of nest boxes but also resulted in the desynchronization of ovulation with eggs being laid equally during day and night. Finally, light spectrum had no major significant effect on feed consumption, body weight gain, stress or aggressiveness.
In conclusion, this work demonstrates that a light bulb within the red spectrum is the best option to promote optimum egg production without any significant impact on feed consumption, health and behaviour.
To that end, Dr. Bédécarrats has entered a partnership with a Canadian company (Thies Electrical Distributing Co.) to develop spectrum lighting LED bulbs suitable for use in barns and a product designed for the egg-laying industry is currently undergoing CSA and Energy Star certification. Follow-up research is currently ongoing to validate the use of this bulb in commercial settings.
PIC Update: Reproductive Maturity and Light
Developing the use of light-emitting diodes
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