By Jane Robinson
Assessing the impact of light intensity on pullet behaviour, growth and bone quality.
By Jane Robinson
Research has confirmed that laying hens headed for aviary-style systems fare much better when they are raised in a similar type of environment. A comprehensive study is underway across Canada that’s looking at several factors of pullet rearing that could impact the successful transition for young birds into more complex layer housing. Led by University of Guelph’s Tina Widowski, the project is looking at factors affecting behaviour as well as musculoskeletal development of pullets.
The researchers identified lighting as one of the performance factors to evaluate in pullet development, and Karen Schwean-Lardner at the University of Saskatchewan (U of S) has recently completed this part of the study, together with her MSc student Jo Ann Chew. U of S offered the ideal setting with its specialized facility designed for lighting work.
The current Canadian code of practice for laying hen lighting is 10 lux. “When hens are in conventional cages, light for manoeuvring through an environment is not as important, as mobility is restricted. But in more complex environments, birds need to learn how to avoid crash landing,” says Schwean-Lardner, an associate professor in the Department of Animal and Poultry Science. “Our goal with this research was to see how light intensity affected the behaviour and bone quality of pullets during the rearing phase.”
With little research reference to draw on, the team’s work would also help provide valuable new insights into the impact of lighting, if any, on pullet development. “Light may impact the ability of pullets to navigate and master more complex spaces,” Schwean-Lardner says.
Three intensity levels
They compared three different light intensities – 10 lux, 30 lux and 50 lux using white LED lights – with pullets from 0 to 16 weeks of age. Birds were raised on the floor in open, perchery-style systems equipped with several parallel perches, a ramp, as well as a drinking line and tube feeders. The study included replicates to compare brown- and white-feathered strains to see if there was a difference in how the strains responded to varying light intensity.
“The perchery set up is not as complex as some aviaries, but it would be an easy rearing system for producers to replicate with birds on one level with a number of perches,” Schwean-Lardner says.
The researchers collected data throughout the birds’ development on body weight, behaviour, jumping frequency and success, fear and stress responses, breast muscle weight, keel bone damage, tibia bone strength and mortality.
Overall, and across all parameters the scientists measured and monitored, pullets showed very little difference between the three levels of light intensity. There were no significant differences in body weight, breast muscle weight, keel and tibia bone strength, fear and stress responses or mortality.
“Our results show that pullets reared in all light intensities were able to successfully and safely navigate their rearing environment,” Chew says. “We saw a small difference in the jumping behaviour but not enough to significantly affect the bone health of the bird.”
Pullets raised under 30 lux and 50 lux lighting jumped more than those in the 10 lux rooms, especially at about four weeks of age. “Higher lighting may be beneficial to birds at a younger age, but there is no difference in bone strength or quality,” Chew explains.
They also observed that birds in the 50 lux room spent more time walking at eight weeks of age, but this activity didn’t translate to any measurable difference for pullets. “If we saw significantly different levels of walking activity, we should have seen difference in bone quality, but we didn’t,” Schwean-Lardner says.
When it came to preening activity, pullets raise in 50 lux spent more time preening at 13 to 16 weeks of age. Those in the 10 lux lighting spent more time pecking. Again, the differences were minor and presented no measurable implications for bird health or development.
“We saw a little more comfort behaviour performance with pullets raised in higher intensity lighting, which might suggest improved welfare, but the differences were minor,” Schwean-Lardner says.
They also found that light intensity produced the same results in both white-feathered and brown-feathered strains. There were the usual differences inherent with white strains being more active and brown strains heavier and calmer.
One of the major surprises was that increasing light intensity didn’t increase fear or stress response in the pullets. “Based on a review of any existing literature on light intensity, I expected we might also find an increase in fear and stress in birds when lighting was more than 30 lux. But we didn’t see that,” Chew says. This could be a result of several factors, including using a one level system, and there could be different results in multi-level rearing systems.
Does lighting matter?
With minimal differences in all the factors examined, the researchers concluded that if producers are using lights between 10 lux and 50 lux to raise pullets, they are providing appropriate lighting. “Our current light intensity recommendations of a minimum of 10 lux for lighting is working, but increasing to 50 lux, with a possibility of more comfort behavioural expression, would not result in behavioural issues either. We saw no more bone breakages and very minor differences when raising pullets in high intensity lighting,” Schwean-Lardner says.
As the first study of its kind in Canada, the results are likely to trigger further studies on light intensity. Schwean-Lardner has lots of ideas for what to look at next. “I am very curious about light intensity in more complex rearing systems than the ones we used in our study, and whether 10 lux would be enough.”
Researchers already know that they way pullets are raised impacts the rest of their productive life. These new insights about the role of light will help inform a more successful transition for laying hens into open-style systems in Canada.
This research is funded by the Canadian Poultry Research Council as part of the Poultry Science Cluster, which is supported by Agriculture and Agri-Food Canada as part of the Canadian Agricultural Partnership, a federal-provincial-territorial initiative. Additional funding was received from Egg Farmers of Canada and Clark’s Poultry.