Layer keel bone fractures can result from perch collisions

A new research study shows the majority of keel bone damage originates from collisions with perches inside the layer house.

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Dr. Maja Makagon, assistant professor of applied animal behavior at University of California, Davis’ Department of Animal Science, presents research findings as part of the Egg Industry Center Egg Industry Issues Forum in Columbus, Ohio. | Austin Alonzo.
Dr. Maja Makagon, assistant professor of applied animal behavior at University of California, Davis’ Department of Animal Science, presents research findings as part of the Egg Industry Center Egg Industry Issues Forum in Columbus, Ohio. | Austin Alonzo.

A new research study shows the majority of keel bone damage originates from collisions with perches inside the layer house.

Dr. Maja Makagon, assistant professor of applied animal behavior at University of California, Davis’ Department of Animal Science, discussed the results of a study conducted to analyze keel bone damage in a layer environment. Makagon, who spoke on April 19 as part of the Egg Industry Center Egg Industry Issues Forum in Columbus, Ohio, said the study utilized accelerometers and 3D imaging technology to study the force of the collisions and measure their effects on the keel bone.

The keel is an extension of the sternum that provides an anchor for the bird’s wing muscles and provides leverage for flight. As laying hens are being removed from a conventional cage environment, Makagon said, keel integrity is increasingly seen as an indicator of animal welfare. Damaged keels are associated with increased mortality, reduced egg production and egg quality, and keel damage is likely associated with pain for the animal.

Methodology

The study, conducted by students and professors from UC Davis, Purdue University, the University of Bern and Michigan State University, analyzed keel damage in an enriched cage environment. Makagon said the study contributes to existing literature on the topic by examining the relationships between the development of keel bone damage, the types and magnitudes of impacts experienced at the keel by hens housed in enriched colony systems and behaviors associated with these impacts.

Makagon said the study used groups of hens housed in enriched cages in a research facility. She said 10 hens were picked at random from each system replication. The selected hens were observed over two, three week trials. The first trial began when the hens were about 52 weeks old and the second at about 74 weeks. As pullets, the birds were raised in a floor environment, she said.

Using cameras to observe the flock as well as the accelerometers, the researchers broke down impacts by the level of G’s, or gravitational force, detected by the accelerometer and categorized those impacts as being due to collisions, grooming, aggressive interaction with other birds, wing flapping or mass scattering. The group studied which action lead to collisions and the object with which the birds collided.

Results

Makagon said more than 80 percent of the impacts greater than 20 G were due to collisions with objects inside the enriched cage. The strongest collisions were greater than 100 G of force. Specifically, 74 percent of collisions were with perches located inside the enriched colony and 30.5 percent of those collisions occurred while birds were ascending onto the perch. The study also determined the number of collisions – rather than the number of keel bone impacts, strength of impacts, or presence of previous fractures – was most likely to negatively affect keel bone integrity.

The study highlights the need for additional research to understand what aspects of the perch – such as height, design, and location – are associated with the risk of keel bone damage and if other variables outside the scope of the study – like the hen’s breed and its housing type – play a role.

The study shouldn’t be seen as a condemnation of perches inside the layer house, Makagon said.

“I don’t want the take away from this to be, ‘Let’s take out the perches,’ certainly not,“ Makagon said. “There’s a lot of good things that they do, but certainly it underscores that really we need to think about how we are designing the systems and how we are designing the various features that go into our system regardless of what the system is.”

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