WEST LAFAYETTE, Ind. – How chickens perceive their environment may be an important factor in egg production in cage free environemtns. 

In order to learn more Purdue University researchers teamed with the U.S. Poultry & Egg Association and U.S. Poultry & Egg Foundation on  a research study to look at how chickens see light.

“The study showed that there are significant differences in the visual systems of brown and white chickens at all ages,” said Darrin Karcher, Purdue University associate professor of animal science, poultry extension specialist, and the study’s principal investigator.

He said the ability of light to transmit through the eye of both brown and white strains (in laying hens) decreased with age, reducing the amount of ultraviolet light that reaches the retina.

“The relative density of cells in the retina consistently differed between the brown and white strains,” he said. “The sensitivity of cells in the retina did not change with age; however, there were unexpected differences found between the brown and white strains.”

“Geneticists have been trying, with little success, to determine and select egg layer strains that will perform well in cage-free production systems because there are numerous, unknown factors which influence a hen’s performance,” Karcher said.

“The unknown factors have resulted in there being no single strain that can perform consistently,” he added. “Companies that have transitioned to cage-free production are faced with various management and welfare issues, including keel bone damage, mislaid eggs, and feet pecking.”

He said these new welfare issues may be due to the hens’ inadequate or inaccurate perception of their environment due to inappropriate lighting.

“No previous studies in poultry have determined how lighting systems can impact hens’ visual perception of their housing environment, or of their conspecifics (a member of the same species),” he said.

He said this project sought to achieve the following objectives: 1) develop a chicken-specific visual model through the collection of physiological information; 2) evaluate lighting systems for spectral properties among different cage-free housing in commercial settings; and 3) explore the relationship between avian visual perception and flock welfare outcomes.

He said initial data to develop the visual models was collected from laying hens housed at Purdue.

“Researchers partnered with a commercial egg producer to collect light spectra during production in a cage-free housing facility,” he said. “Models were executed to identify whether high or low conspicuousness of different objects from the hens’ viewpoint could be related with variations in welfare indicators under different cage-free housing and lighting systems.

Due to the highly pathogenic avian influenza outbreak across the country during the project period, he said researchers were unable to visit as many facilities to evaluate lighting systems for spectral properties among different cage-free housing in commercial settings, or assess the welfare indicators initially to explore the relationship between avian visual perception and flock welfare outcomes.

However, he added, “Researchers were able to fully develop the visual models from two strains of chickens (brown and white) at three different ages (17, 25 and 85 weeks of age) to model the visual environment at two different facilities.”

In cage-free egg laying facilities, he said, modeling revealed that the visual environment is often homogeneous and undistinctive, except when highly colored objects are present, potentially increasing the risk of injury to the hens as they move through the aviary.

“The ambient light in the egg-laying facility impacts how conspicuous objects and substrates (the surface or material on or from which an organism lives, grows, or obtains its nourishment) are,” he said. “In certain ambient light conditions, the strain and age of the laying hens determined if an object was easily perceived.

“Overall, variability in the visual systems of different strains and ages of laying hens should be considered when determining aspects of the visual environments that are utilized in the industry,” he added.

In 2022, Iowa State University studied effects of visual stimuli, but not regarding resource use. Published by Frontiers of Science, the research focused on the immunological benefits that may be gained through use of virtual reality and visual stimulus for chickens.

Melha Melata, Iowa State associate professor of food science and human nutrition, presented this work at the Egg Industry Issues Forum held by the Egg Industry Center in November 2022.

Brett Ramirez, Iowa State assistant professor of agricultural and biosystems engineering, and assistant director of the Egg Industry Center, said Purdue’s new study shows some promise in helping the U.S. egg industry better understand the animals it cares for day in and day out.

“Research like this can help prompt additional analysis in areas like lighting and equipment design,” he said. “Depending on those results, the industry can make changes to help the birds navigate their living environments even better than they are today.

“While new lighting protocols and equipment advances take time to implement, changes in the industry usually start with a research discovery such as this one,” he added.