What Problem Do Windows Solve?

Our thoughts on the recommendations to install windows into poultry houses.


Innovation typically comes from recognizing a problem, proposing a logical and cost-effective solution, implementing the solution in a limited way and collecting data to prove or disprove the efficacy of the solution before rolling it out on a greater scale. Taking into consideration food security, as well animal health and welfare (i.e. “the problem”), nearly all recent poultry house construction has been closed and tunnel-ventilated designs (i.e. “the solution”).  Most of the challenges associated with this innovation have been addressed through technology and automation.

Lately poultry producers have been heavily influenced to install windows into closed, tunnel-ventilated housing, adding natural light to improve animal welfare. These decisions were encouraged with little to no proven benefit on the animals, making it difficult to see the problem or the benefit of this “solution”, with respect to the above description of innovation and the reason this recommendation deserves a closer look.

The installation of windows in poultry housing identifies that light is essential to raising animals in indoor facilities to achieve optimal results. This premise also provides the foundation at ONCE®, who dedicates every extra penny into researching the interaction of animals with light.  As a scientific organization, the installation of windows is puzzling.

Much like the sun, ONCE® provides a complete lighting system that replicates the photoperiod and intensity of a chickens natural habitat. The species-specific light wavelengths direct desirable behaviors and biochemical responses, while providing a non-seasonal, consistent and lower-stress environment.  In fact, ONCE® has proven that broilers raised under our lighting systems experience reduced stress markers by up to 50% through 3x less corticosterone, 2x lower H:L ratios and lower body asymmetry. In effect, demonstrating that a “natural light environment” can be provided by a properly researched and designed lighting system.

Additionally, ONCE® has recently identified the importance of ultraviolet (UV) light when raising animals indoors. Although a natural light spectrum provided by the sun, it is oftentimes missing indoors. UV light is shown to further lower animal stress, making the pressure to install windows up for debate, however commercially available windows filter out the desired UV wavelengths.

Leaving the question, what enrichment do windows provide?  The decision to add windows was likely an anthropomorphic one. Humans like windows, so poultry must like windows too. But do bright squares of filtered sunlight on the poultry house floor represent a natural environment?  Do chickens like this environment? The only way to know is likely through blood assays of stress markers, and this work has not been done.