The Power of Light: How Gradient Lighting Boosts Broiler Production

The Benefits of Artificial Gradient Lighting for Broilers
Many animals perceive light differently than humans. For example, poultry vision and color
perception are much more sophisticated than human color perception. This is due to differences
in the number of cone photoreceptor types present in the retinas of humans versus poultry.
Poultry have four types of retinal cone photoreceptors in their retinas, which allows them to
perceive a broader portion of the light spectrum than humans, who only have three types of
cone photoreceptors. Poultry and other avian species also have oil droplets in their cone
photoreceptors that filter light entering the retina, allowing birds to discriminate between
wavelengths better than humans. Poultry can see twelve times better in the blue spectrum and
four times better in the red spectrum and can even see UV-A light. 

Due to the photosensitive nature of poultry, artificial lighting in commercial barns can be very
impactful on poultry performance and welfare. In a recent publication, “Effects Kang et al”
evaluated the effects of variable (gradient) artificial lighting compared to uniform lighting at 5 lux,
uniform lighting at 20 lux, and sunlight. This group demonstrated gradient lighting reduced the
overall number of birds culled due to leg issues, reduced mortality, improved feed conversion
ratio (FCR), and improved daily weight gain compared to sunlight provided through windows.
Let’s explore these further.

Reduced overall number of birds culled due to leg issues and reduced mortality
Leg issues in birds can result in high mortality rates and compromised bird welfare. Kang et al.
(2023) showed birds treated with gradient light had the lowest number of birds culled, due to leg
issues compared to the other three treatments, and lowest total mortality compared sunlight.
Compared to the 20 lux treatment, birds reared under gradient lighting were significantly more
active on a daily basis between d39-42. This suggests that increased daily physical activity in
the gradient lighting group improved leg health and consequently reduced bird mortality. These
results indicate both the economic and animal welfare benefits of using artificial lighting in
broiler production.

Improved feed conversion ratio (FCR)
Over the course of four trials, the average feed conversion ratio (FCR) - the ratio of given feed
weight over animal weight gain in a certain period – for the gradient light treatment was 2.2%
lower than the sunlight treatment. These results further demonstrate the beneficial effects of
gradient artificial lighting over sunlight on the performance of commercial broilers.
Increased daily weight gain compared to sunlight provided through windows
In addition to lower FCR, Kang et al. (2023) also observed that the average daily weight gain for
birds reared with gradient lighting was 4.1% higher compared to birds reared with sunlight.
Broilers that are converting feed more efficiently to muscle and continuing to gain weight have
the potential to reduce feed waste and increase profitability at harvest.

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