Smothering occurs when birds mass together, often on top of each other, which can result in death from suffocation.

The project was funded by McDonald’s UK as part of its Farm Forward programme and undertaken by FAI Farms, together with its suppliers Noble Foods Ltd and The Lakes Free Range Egg Company who form part of the Sustainable Egg Supply Group.

The first phase of the project, published in 2014, revealed that more than half of commercial free range laying hen flocks are affected by smothering.

This second phase explored the relationships between frequency of smothering and bird health, as well as housing design and management practices. Whilst the researchers found no relationship between health and incidences of smothering, particular management techniques and system designs did have an effect.

Speaking of the project, Annie Rayner, Research Scientist at FAI, said: “This research has raised the industry’s understanding of the welfare and economic implications of smothering and we are beginning to learn what actions are needed to address the underlying causes of this serious problem.”

Smothering in the nest boxes was found to be affected by both the breed of bird and the type of nest box design. Nest box design was also found to affect smothering occurring outside of the nestboxes, perhaps reflecting different layouts of housing.

McDonald’s urged nest box manufacturers to consider the issue of hen smothering in future designs.

Feeding grit or grain on the litter was found specifically to reduce smothering that occur away from the nestbox, and other findings suggest that the provision of tree canopy cover on ranges may be important.

Connor McVeigh, Supply Chain Director, McDonald’s UK commented: “While there are some on farm measures farmers can take to reduce the chance of smothering occurring, it’s clear that the industry needs a joined up approach to tackle this problem.”