Just the facts. From the experts.


Housing systems for egg-laying hens is a topic that has gained increased attention in recent years, especially in light of proposed federal legislation on the issue. A national study is taking a thorough look at the well-being of not only the birds housed on these farms, but also the people who care for them.


Coalition for Sustainable Egg Supply (CSES), an organization comprised of scientists, food companies, research institutions, non-governmental organizations and other groups, is halfway through a three-year study of three housing systems:


1.  Cage-Free Aviary Housing (includes nests, perches and scratch areas):



2. Enriched Colony Housing (includes nests, perches and scratch areas):



3. Traditional Caged Housing (currently used by a vast majority of today’s egg farms):


The research team seeks information about why worker safety might be different in the each housing system and the aspects of each system that might impact respiratory health. For example, enriched systems might be considered better than caged because there are fewer birds. Conversely a cage-free system might have higher levels of airborne materials because of bedding material on the floor and birds being able to move around more freely. 


We spoke with Dr. Diane Mitchell, a research associate in Epidemiology at the University of California-Davis, who is involved in the worker safety aspect of the study.


Best Food Facts: When it comes to egg production, we typically hear about animal health and well-being. In this case, you’re focusing on the humans that serve as caregivers to the animals. Why is this important?

Mitchell: "Farmworkers, especially those working in enclosed buildings with large numbers of animals, can be at high risk for respiratory health problems. It is thought that the effects are due to a combination of their exposures to complex mixes of airborne pollutants and gases. Organic particles become airborne when hens are active and as workers move around in the barns. The most frequently observed effect has been asthma-like symptoms. So, the health of the worker is a serious concern when comparing different systems of egg-laying facilities."


Best Food Facts: Have there been any previous studies that consider worker health in the poultry industry? If so, what is this new study addressing that previous studies haven’t?

Mitchell: "There are only a few studies of worker health comparing systems in which hens are kept in cages with indoor cage-free housing. And, most of the cage-free housing studies have been for broilers (chickens raised for meat) rather than laying hens.  None of them have compared all three housing systems that are present in the commercial-sized facility that was constructed for the purposes of the CSES study. As these other studies are carried out in many different facilities with different management practices, it makes it more difficult to compare systems.

"Our advantage in the CSES study is that we have a more controlled comparison with consistent management practices. The same people work in all three systems so we will be able to determine what air pollutants they are exposed to in each type of housing. We will compare their breathing and lung function at the end of their shifts to when they started work in the morning, and hope to see if any one type of housing is worse or better."  


Best Food Facts: To analyze the health and welfare of the people working on these farms, what factors are being considered in your monitoring?

Mitchell: "My research is examining the respiratory exposures and health of the people; other researchers are evaluating ergonomics, other physical aspects of their work. Samples are collected in the air that the workers breathe, and ammonia levels are monitored. We are documenting symptoms by having the people fill out questionnaires and performing pulmonary function tests to compare health outcomes at the end of their shift to the beginning.

"The season of the year, the ventilation rate of the building, the number of hens and total air volume in the housing, the ages of the hens, and the length of time the workers wear respiratory protection are also being taken into consideration."


Best Food Facts: Based on you preliminary observations, do you think the outcomes of the research will be immediately actionable to those in egg and poultry production?

Mitchell: "The study is set up to be a holistic comparison of the three types of layer housing, so until all information is gathered, analyzed and prioritized, I cannot predict the outcome. From the health perspective, whatever the results, I would hope the respiratory exposure data will encourage workers to increase their use of effective respiratory protective masks and respirators."


The Coalition for Sustainable Egg Supply is currently conducting a commercial-scale study of housing alternatives for egg-laying hens in the U.S. The first research flock was placed in April 2011. The study will be replicated over two flocks with conclusion in 2014 and results reporting to follow.

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