The Food Journal and Food, Nutrition & Science

An alliance between The Lempert Report and The Center for Food Integrity

The Quest for Egg Sustainability

The Quest for Egg Sustainability

The Food Journal

March 26, 2015

There’s been a lot of talk about eggs lately. Always a popular, protein-packed breakfast food, Americans enjoy their eggs. In fact, U.S. egg production totaled 95.2 billion in 2013. And while some consumers may have avoided eggs in the past due to cholesterol-related health considerations, the 2015 Report of the Dietary Guidelines Advisory Committee recently announced that cholesterol is not a nutrient of concern for overconsumption, so more consumers may be embracing eggs soon. Even Kevin Bacon is encouraging us in a creative ad campaign to eat more eggs.

But eggs and the way in which they are produced have also faced questions about their sustainability including criticisms from environmental groups about the various methods in which hens are housed. Indeed, the rise in the demand for free-range or cage-free eggs has been dramatic, as has the demand for alternative hen housing systems. However, the majority of hens are still raised in cage systems.

According to the American Egg Board, roughly five to six percent of hens are in cage-free systems, which include barn and aviary systems. The remaining 94-95 percent are in cage systems. The latest hen inventory estimate comes from USDA (Feb 2015) at 304.7 million laying hens. USDA reports that per capita egg consumption grew to nearly 255 in 2014, which is the highest in 30 years. According to Nielsen more than 2.24 billion shell eggs (UPC coded) were sold at retail last year in all outlets combined, up 1.6 percent from 2.21 billion in 2013. The dollar value of eggs sold in 2014 is $5.92 billion, up 10.6 percent from $5.36 billion in calendar 2013.

Hen Housing Research Explained

As consumers become more interested in where their food comes from and food producers respond, the way in which eggs are produced gets more and more scrutiny, and requires more research and improved communication with consumers. One important three-year study, The Laying Hen Housing Research Project, was just released under the collaboration of The Coalition for Sustainable Egg Supply.

The objective of the study was to evaluate three laying hen housing systems – conventional, enriched and cage-free – by considering the impact of multiple variables on a sustainable system. Why? Because research in this area of commercial-scale egg production was lacking, and a better understanding of the impacts of production on food safety, the environment, hen health and well-being, worker health and safety and food availability could help guide informed production as well as purchasing decisions.

How Are Hens Housed?

The vast majority of eggs used by the U.S. food system today are produced in the conventional cage system. To represent a conventional cage system in this study, hens were housed in multilevel rows of enclosures with wire mesh floors. There were six hens per enclosure, with each hen provided 80 square inches to meet customer requirements (conventional systems can range from 67-86 square inches per hen; 80 square inches was specific to this study). A manure belt below the cages kept manure away from the hens, while wire floors sloped slightly so eggs rolled down to an egg-collection belt.

In the enriched colony, hens were housed in multilevel rows of enclosures with wire mesh floors. There were 60 hens per cage with each hen provided 116 square inches. There is enough space for each hen to stand, sit, turn around and extend her wings, while also allowing for natural bird behaviors like perching, scratching, dust bathing and nesting. Nesting hens also have access to privacy curtains. A manure belt below the cages kept manure away from the hens, while wire floors sloped slightly so eggs rolled down to an egg-collection belt.

In the cage-free aviary, hens were allowed to roam freely in defined sectors of the building, with 144 square inches per hen. There was open floor space as well as multiple levels for hens to perform natural bird behaviors, like perching, scratching, dust bathing and nesting. A manure belt below the cages kept manure away from the hens, though some manure was also in the floor area. 

But What Exactly Is “Free-Range”?

While the system was not researched by CSES, most people think of chickens roaming around the barnyard when they think of free-range. But there is actually no precise federal government definition of “free-range,” so the USDA approves these label claims on a case-by-case basis, says Gwen Venable, Vice President of Communications for the U.S. Poultry & Egg Association. USDA generally permits the term to be used if chickens have access to the outdoors for at least some part of the day whether the chickens choose to go outside or not. Cage-free hens differ slightly from free-range hens in that they are uncaged inside barns, but they usually don’t have access to the outside.

USDA does not specify the quality of the outside area, the amount of outside area or the duration of time spent outside. And free-range chickens can eat anything that they find outside including waste, bugs, grass and seeds. In addition, one of the biggest problems facing growers today is the threat of avian influenza as a result of migratory birds. Family farms take great measures, says Venable, to protect and isolate their chickens from disease, and that is one reason why commercial poultry production evolved to providing indoor housing for poultry.

In practice, most chickens stay close to water and feed that is usually located within the poultry house. Chicken labeled as “organic” must also be “free-range,” but not all “free-range” chicken is also “organic.” Currently, fewer than than one percent of chickens nationwide are raised as “free-range.” 

“Free-range chickens face a variety of dangers such as predators, weather, and disease. Commercial poultry is raised on family farms in which the birds are raised in large, spacious barns. These barns are sophisticated, secure facilities with strictly controlled temperature, humidity and ventilation systems inside – which provide vital protection from the outdoor elements, disease and predators,” says Venable.

Hen-Raising Challenges

All current housing systems, be it free-range, cage-free aviary, or conventional cage system, suffer from feather pecking and yes, cannibalism as the result of pecking order. Pecking order refers to a dominance hierarchy, seen especially in domestic poultry, which is maintained by one bird pecking another of lower status. Unfortunately, this can lead to suffering and death in laying hens that have not been beak trimmed, which is why beak trimming was introduced as a routine husbandry procedure.

“Vent cannibalism is a distressing problem that involves hens consuming other (live) hens, with the cannibalism usually starting at the vent area shortly after an egg is laid. Despite a great deal of study, we still don’t completely understand what causes it or how it can be prevented. It is also what we call an ‘episodic’ problem – meaning that an egg producer could have a flock (including a cage-free flock) that has little or no cannibalism, but then have an outbreak in the next flock even though nothing obvious has changed in terms of the way the hens are managed or housed. Again, why this happens isn’t clear,” says Dr. Joy Mench, CSES co-scientific director, and professor of animal science at the University of California, Davis.

However, says Mench, cannibalism does tend to be more of a problem in larger flocks (like cage-free flocks), probably because once it starts the hens “copy” one another’s behavior, so the behavior spreads through the flock. 

“Obviously, being cannibalized is painful. Being caught in the structure and excessively pecked would also cause distress to the affected hens,” says Mench.

Domestically-raised birds, no matter how they are housed, also suffer from a variety of other conditions including hypocalcemia (low blood calcium levels), foot problems and egg yolk peritonitis (a common cause of abdominal distention).

Where Does Food And Worker Safety Factor In?

The CSES study found no difference in the detection of Salmonella spp. or Campylobacter spp. between the eggs produced in the three commercial housing systems monitored. Management of housing systems to encourage nest box usage, when they are present, and to control dust are key to enhancing the safety of eggs produced in any hen housing system. 

“With appropriate management, any hen housing system can produce safe eggs,” says Dr. Deana Jones, research food technologist, USDA Agricultural Research Service, and CSES researcher. 

Still, this study confirmed the general consensus that cage-free aviary systems, because there is litter on the floor and some eggs must be hand collected, greatly increase particle air pollution in egg-laying housing, which can be dangerous to farm workers.

Consequently it is very important that workers in cage-free aviary systems consistently wear a high level of respiratory protection – either N95 masks or full respirators. Those workers must be trained to wear respiratory protection during most of each work shift and especially when tasks increase the concentration of dust in the air. 

“Because the specific aviary style used in this study allows eggs to be laid outside the automated egg collection system, more workers are needed compared to the other caged housings. In addition, there are likely to be ergonomic problems encountered over time, when workers have to repeatedly crawl, lie down and use extended postures to retrieve those eggs,” says Diane Mitchell, staff research associate in epidemiology at the University of California, Davis, and CSES researcher.  

What Can We Afford?

At 10 percent interest and depreciation, the cage-free aviary system has total capital costs per dozen eggs that were 179 percent higher than the conventional cage system, while the enriched colony system had total capital costs per dozen eggs that were 106 percent higher than conventional cage.

Ultimately, the study found that cage-free eggs cost 36 percent more to produce than conventional eggs. “The average retail expenditure for eggs is about $120 per year for a family of four. Raise that by 50 percent and the total is about $60 more for a year. That is significant amount for some consumers who consume eggs as the lowest-cost source of animal protein,” says Dr. Dan Sumner, director, University of California, Davis, Agricultural Issues Center, and CSES researcher. 

What Consumers Should Know

The vast majority of poultry farms in the United States are owned and operated by families, says Venable. Contrary to the misconception that farms are industrial operations owned by large corporations, family farms make up 97 percent of all American farms. Incredibly, these family farms account for 82 percent of agricultural production in the United States.

Egg farmers in the U.S. continue to modernize egg farming production and processing practices to meet the demand for nutritious, high-quality eggs. Hen health and egg quality are the two main priorities on egg farms. Egg farmers follow guidelines to ensure the hens are provided with nutritious feed, clean water, proper lighting and fresh air. America’s egg farmers produce a high-quality product that provides all-natural, high-quality protein; and according to the United States Department of Agriculture (USDA), eggs are now 14 percent lower in cholesterol (down from 215 mg to 185 mg) and 64 percent higher in vitamin D. 

“The commercial layer industry has been phasing from caged housing to newer systems that meet many consumer’s demands. This continuing progression in animal housing provides 70 percent more space,” says Venable.

As far as sustainability is concerned, the CSES study underscores the importance of looking at the big picture and the different risks and benefits of each housing system. While energy costs were consistent across all systems, capital costs per dozen were much higher for cage-free aviary and enriched colony systems than the conventional cage system. Labor costs were highest in the cage-free aviary system as well. Cage-free aviaries provide more behavioral opportunities and chances to develop better bone strength, but they also provide increased opportunities for hen pecking and higher hen mortality.

Dr. Mench adds, “No hen housing system is ideal in all respects – all of them have trade-offs that should be considered by consumers when making decisions about their egg purchases. Doing so allows them to make purchasing decisions that best meet their values.”


The final research results from CSES can be accessed at, including the complete research report, a summary report, and an interactive infographic profiling the trade-offs involved in each of the housing systems.