The Science Behind Flicker: What is it? And how does it impact poultry?

Most of us are familiar with the common definition of “flicker,” a light or source of light that shines unsteadily or varies rapidly in brightness, but we may not realize how flicker can impact agriculture lighting and, in turn, poultry. For this we need to look at Temporal Light Modulation (TLM) - how light changes over time - which impacts the intensity of the color. The way humans and other animals perceive that change - what we see directly, is the flicker. 

Let’s explore the basics of flicker and how it impacts variables like body weight, stress levels, and mortality in poultry.

Just like us chickens 

Did you know there’s a calculation to determine the size of the flicker percentage, or the visibility of flicker? It’s called the Pst correlation, and it shows the probability of a flicker. If you want to predict how visible flicker will be, you should use a model like this. Pst, though, is designed for humans and the question remains how to go from humans to birds.

The first step in making this transition is understanding something known as the critical fusion frequency which means, essentially, that the more frequent something becomes, the less you notice it. Factors ranging from dyslexia to caffeine intake can impact how much flicker a human perceives, and factors like species and how fast they fly can impact a bird’s flicker perception. Chickens, in fact, are very similar to how a human perceives flicker.

Based on this insight, we built something called the Avian Flicker Visibility Measure (AFVM) to determine whether or not birds see flicker. We also offer the only available meter that can record AFVM. 

Flicker’s impact on poultry

While we know that lighting can affect poultry behavior and physiological functioning, which in turn impacts bird productivity and welfare, we don’t know as much about light flicker. As background, there are three levels of flicker we need to concern ourselves with:

1. Conscious perception - That which the brain identifies, and we (or the birds) can see. Hens have a conscious perception up to 105 Hz. Humans have a conscious perception up to 50 Hz. 
2. Unconscious perception - That which the brain identifies, and we (or the birds) can’t see. Hens have an unconscious perception up to 119 Hz.
3. That which the brain can’t identify, nor can we see. 

Previous research on the impact of flicker on birds doesn’t tell us much, and what does exist points to conflicting results. Fortunately, we have a facility where we conduct lighting research and set out to see if we can gain clarity regarding flicker’s impact on poultry. 

We conducted two experiments, repeating each one, on leghorn pullets and turkey hens, seeking to determine how light flicker impacts productivity, health, behavior, and welfare. 

Here is a summary of our findings related to studying more than 5,000 layer pullets, using three light flicker frequencies (30 Hz - obvious to all, 90 Hz - humans can’t see but birds might, and 250 Hz - can’t see) over a 16-week period:

• No impact on body weight or stress levels 
• Overall mortality affected by both visible and near-visible flicker
• Increased amount of time standing and increased aggressive behavior 
• Environmental pecking, typically seen as a positive sign, decreased

Here is a summary of our findings for a study on 3,276 turkey hens at 4, 8, and 11 years of age, using a similar system as the pullets:

• No impact on body weight up to 8 weeks of age
• Reduction in feed consumption 
• Overall mortality affected by flicker up to 11 weeks of age
• Gentle feather pecking, also typically seen as a positive sign, decreased 
• Increased stress levels at 11 weeks of age 

What we know about flicker as it relates to birds

In conclusion, while there is still more work that needs to be done, we know that as it relates to birds, flicker:

• Affects early life, which becomes more obvious with faster-growing birds 
• Birds appear to adapt, at least in terms of most productivity parameters 
• Impacts mortality
• Impacts stress levels, although it should be noted that our research facility is likely a less stressful environment than most barns

Listen to our webinar
For a more detailed overview of flicker and its effect on poultry, listen to our webinar, “The Science Behind Flicker: What is it and how does it affect poultry?” featuring Dr. Karen Schwean-Lardner of University of Saskatchewan and ONCE by Signify lighting expert Dr. Dragan Sekulovksi and hosted by our Research and Innovation Director Dr. Aaron Stephan.

Contact one of our animal lighting experts who can answer any questions you have about flicker and its effect on poultry and a whole host of other issues.