Pullet Behavioural Research: Flee or freeze

As laying hens convert to open-concept housing, with more opportunities to move, the question of how they respond to fearful situations may factor into the choice of aviary rearing style. New research at the University of Guelph evaluated how different aviary rearing styles, as well as genetic strain, feed into fearfulness in pullets.

“Research has already discovered that birds reared in cages are more fearful than those reared in aviary housing – those from cages tend to freeze in the face of fear, and birds from aviaries tend to flee,” says Dr. Tina Widowski, Egg Farmers of Canada Chair in Poultry Welfare at the University of Guelph.

What wasn’t known was if there is a difference in fear response for birds raised in the different styles of aviary housing used in Canada. The styles differ in the level of complexity – number of platforms and perches – offered to young birds. Widowski and her PhD graduate student Ana Rentsch led a new research project, the first to evaluate fearfulness in pullets raised in different styles of aviaries.

The fear with fear
When birds are exposed to new, unfamiliar situations – spaces and objects – there is an increased risk of injury if they flee or if there is mass panic in open-style housing that could lead to piling or smothering. All these reactions can have economic and welfare implications for the birds and for producers.

“Fear is very subjective and tough to measure, so we look at how the birds respond and their behaviours when presented with potentially frightening situations,” Rentsch says.

The research involved exposing pullets to situations that may cause fear and observing their behaviour. Rentsch compared the response in pullets raised in three aviary styles that offering varying degrees of complexity, including the number of perches, levels and ramps available to the birds.

“The styles ranged from very simple to very complex where chicks had the full run of the space from day one with multiple platforms and perches,” Rentsch says. “We also included conventional pullet rearing cages for comparison with the bare minimum of complexity.”

Birds were presented with situations similar to what they would experience in a normal rearing environment, especially in aviary housing, that included a new space and new objects introduced within that space.

The testing arena
Two birds from each different rearing aviary, as well as from caged-rearing, were placed at the edge of a new circular space at 14 weeks of age. Rentsch noted how much they explored the space and how long it took them to move to the centre. “We presume that if birds explore a lot they are likely less fearful because they feel comfortable in the space,” Rentsch says. “And as a prey animal always on alert about potential predators, the faster birds moved into the centre (more exposed area of the space) the less fearful we assume they are.” Behaviour and response of brown-feathered and white-feathered birds was also measured.

Rentsch recorded other types of behaviour in the space to gauge how agitated the birds were, including exhibiting an outstretched neck or escape attempts.

After a few minutes in this new space, an object was lowered from the ceiling into the centre of the space, and again, response was measured based on the style of housing and feather colour. They looked at whether the birds moved away (walking, jumping or flying) to avoid the object, or if they stayed put.

Staying calm amid complexity
As expected, birds in all three aviary styles were calmer than birds raised in conventional cages.

When the object was introduced to cage-reared birds, they didn’t move the entire time they were observed. “This probably means they were frozen in fear,” Rentsch says. “While the birds in aviaries approached and investigated the object which leads us to believe they were less fearful.”

The researchers did find some interesting difference in fearfulness between the three styles of aviary housing.

Based on the fact that aviary-raised birds tend to be more reactive and fly away more than conventional cage-raised birds, they actually found birds raised in the most complex aviary style were less likely to have a flight response when faced with a potentially fearful situation.

“Birds in the low and medium complexity aviaries were very reactive at first with the object, and then recovered quickly,” Rentsch says. “While the birds in the most complex aviary did not react at all. They stayed where they were when the object was lowered into the space and then approached it and investigated it.”

Birds reared in highly complex aviaries appear to be calmer in the face of fear, and Rentsch and Widowski are the first researchers to show these differences in fearfulness between the different aviary housing styles.

“We also found that white-feathered and brown-feathered birds reacted differently,” Rentsch says. “We can’t say that one is more fearful, they just have different responses.” Brown birds were more agitated in the new space. 

And when the object appeared, white birds were more likely to flee from it while brown birds had a more stationary, stay-put response.

Take home messages
“We know birds need to be smart, calm and physically fit to manage in aviary housing systems,” Widowski says. “And when they are young, they need to be prepared because there are a lot of challenges. This work has demonstrated the importance, once again, of rearing pullets in environment that will prepare them for a long, healthy productive life.”

From Rentsch’s perspective, she has a few take home messages for producers about fearfulness.

Be aware of the differences between white- and brown-feathered birds when it comes to fear responses and reactivity, especially if you are considering switching genetics.

Choose an aviary rearing style that works for your management and staff. More complex aviaries that provide more freedom for the birds, also require more management.

Talk to other producers who are already using various rearing styles to find out about their experiences.

Don’t avoid providing the birds with novel objects (extra enrichments) and experiences during rearing. It’s important to expose birds to potentially frightening situations so they become familiar and more robust as adults. 

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, Egg Farmers of Alberta and the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) through the Ontario Agri-Food Innovation Alliance.