New study guides poultry farmers on choosing eggs-actly the right hen housing system

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Janice Siegford is part of the CSES team working to ensure safe and sustainable housing for laying hens. (view larger image)

EAST LANSING, Mich.—It’s not the “which came first—the chicken or the egg” debate but rather an industry need for information to guide production and purchasing decisions about sustainable laying hens housing that spurred a $6 million commercial-scale study by the Coalition for Sustainable Egg Supply (CSES).

The study, led by scientists from Michigan State University and the University of California, Davis (UCD), assessed three laying hen housing systems: cage-free aviary, enriched colony and conventional cage. The housing systems were evaluated on their potential impacts on food safety, hen health and well-being, the environment, worker health and safety, and food affordability.

“The goal is and remains to be keeping egg laying a sustainable and viable industry in Michigan—where it’s a $229 million a year industry—and in North America,” said Janice Siegford, MSU Department of Animal Science assistant professor and CSES project research team member.

The results show that the three systems each have associated trade-offs across varying elements of sustainability. The complete research report and other research insights exploring the trade-offs associated with each system can be found at

The information will help producers, egg retailers, restaurants, suppliers and other stakeholders to make independent decisions that are ethically grounded, scientifically verified, economically viable and, ultimately, in alignment with the values of their customers and consumers.

“Before CSES, commercial-scale research evaluating the various aspects of the sustainability of hen housing systems was lacking, and a more holistic, integrative approach was necessary,” said Janice Swanson, CSES scientific co-director and MSU animal science professor. “With these science-based research results, we have a better understanding of hen housing sustainability and can provide that information to industry stakeholders to support informed decision making.”

The study, which spanned four years and two hen flock cycles, involved researchers from three universities and a government agency. The activities were prompted in part by a law passed in 2012 by the European Union that requires all commercial eggs to be produced in free-range barns or enriched cages, thus essentially banning conventional housing for hens.

Several U.S. states have already passed legislation to change hen housing. The Michigan Animal Industry Act, passed in 2009, gives producers 10 years to adopt the new standards. The law doesn’t ban conventional housing but requires that hens be able to stretch their wings without coming into contact with the cage, freely move around and lie down.

Three hen housing systems were studied:

  • Conventional cage housing has small cages housing four to nine hens. There may be thousands of cages per house, often housing 200,000 hens in each building.
  • Enriched colony systems house 60 to 250 hens in more open cages that are larger and equipped with perches, nesting areas and material to facilitate foraging and dust bathing. These systems can house up to 100,000 or more hens in each building.
  • Cage-free aviary systems allow hens to roam throughout various sized sections of a building. Each section contains perches, nesting areas and dust-bathing material. There can be up to  80,000 or more hens per building.

“The conventional system is efficient and good for controlling disease and for environmental containment because manure is taken away constantly on a conveyer belt,” Siegford said. “However, the hens are confined to a very small space. They don’t have room to do chicken-type things – scratching the grass, pecking at bugs, dust bathing or perching on something.

“In the alternative housing systems, hens have opportunities to perform a wider range of behaviors, but some of these behaviors, such as pecking the feathers of other hens, may cause problems. All of the systems have trade-offs, with strengths and weaknesses in different areas.”  

Siegford’s research—in collaboration with Dana Campbell, MSU animal science research associate—looked at hen behavior in the cage-free aviary systems. Former MSU scientist Michael Orth, now with Texas Tech University, and Darrin Karcher, an MSU Extension specialist, examined bone health, and Richard Fulton, MSU veterinary medicine professor, measured attributes of health and causes of mortality in the flock. For this aspect of the project, researchers studied two large hen flocks over two years at a commercial egg-laying operation.

The research team from UCD focused on hen behavior and welfare in the enriched colony system. In all three systems, UCD researchers conducted hen welfare audits, measured human health impacts, food affordability and manure storage emissions. Scientists with the Agricultural Research Service of the U.S. Department of Agriculture conducted the research on egg quality and food safety.

Findings showed that workers in the cage-free aviary houses were exposed to higher levels of dust and bacteria than those working in the conventional cage or enriched colony housing. This increased exposure is due in part to the effects of litter that accumulates on the floor. Egg quality was the same in all housing systems.

Siegford said the data represents a significant milestone in understanding the impacts and trade-offs associated with each system. She hopes to conduct further studies looking at individual use of space in the aviary housing system with emphasis on animal welfare.

“We need more research to see scientifically how hens do in these systems because not all hens use the systems the same way,” Siegford said. “But the preliminary findings combined with future data will greatly increase our scientific knowledge about sustainable egg production. That’s something we can use to inform egg producers and people making purchasing decisions.”

CSES, which was facilitated by the Center for Food Integrity, is a multistakeholder coalition of leading animal welfare scientists, academic institutions, non-government organizations, egg suppliers, and restaurant/foodservice and food retail companies. In addition to MSU and UCD, researchers from Iowa State University, USDA ARS and Cargill also contributed to the study.

Visit for more information about the Coalition for Sustainable Egg Supply. 

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