CSES compares production trade-offs in laying hen housing

Data offer insight into variables to be considered when selecting among different hen housing systems.

The Coalition for Sustainable Egg Supply (CSES), nearing completion of a two-flock research study to better understand the sustainability impacts of various types of laying hen housing — including cage-free aviary, enriched cage and conventional cage systems — has released preliminary research results.

Over the course of three years and two separate flocks, the research assessed five areas of sustainability: animal health and well-being, environmental impact, food affordability, food safety and worker health and safety, CSES said. A complete overview of the preliminary results is available at www2.sustainableeggcoalition.org.

While the initial findings should be treated as preliminary and have not been subject to peer review, CSES said the data begin to offer some insight into the variables to be considered when selecting among the different hen housing systems.

Animal health, well-being

Egg production through the first half of the flock cycles for each system remained fairly similar, with production from the aviary system declining most through the remainder of the cycle, in part due to its higher hen mortality, CSES said. In total, production from the enriched colony system was approximately 3% higher than that of the conventional system and 6-10% higher than production in the aviary system.

The research findings found that pullets reared in the aviary system had better skeletal integrity than those reared in conventional cages, the coalition reported. Hens in the aviary and enriched systems had a higher incidence of keel bone deviations and/or fractures than hens in the conventional system. However, hens in the conventional system had the highest incidence of foot problems, mainly hyperkeratosis. When hens in the aviary did have foot problems, they were more severe than those in the conventional or enriched systems, CSES noted.

The coalition said the findings also showed that hens in the conventional and enriched systems had cleaner feathers but worse feather cover than aviary hens. Hens with large areas of feather loss lost more body heat than better-feathered hens.

Environmental impact

The research assessed the environmental impact of each of the three systems, including indoor air quality, air emissions and energy use.

Regarding indoor air quality, CSES said daily mean ammonia concentrations were less than 15 parts per million in both conventional and enriched cage houses throughout monitoring period, but higher ammonia concentrations in the aviary house exceeded 25 ppm and resulted from accumulation of some manure on the floor that was not removed until the end of the flock, as well as the building's low ventilation rate in the winter.

Further, particulate matter (PM) concentrations in the aviary house were roughly 8-10 times those in the conventional and enriched cage houses, which were by and large similar, CSES noted. Similarly, the aviary system had 6-7 times the PM emissions compared to the other two systems. The higher PM levels and emissions were caused by hens performing activities on the litter floor, the coalition explained.


Farm costs per dozen eggs were highest for eggs produced in the aviary system, followed by those from enriched housing and then conventional housing, CSES noted.

In total and driven largely by higher feed, labor, pullet and capital costs, the aviary system was 36% more expensive to produce eggs in than the conventional system, while the enriched system was 13% more expensive — primarily due to capital costs per dozen — than the conventional system, CSES explained.

Food safety

Eggs from each of the three systems were assessed for quality at two days post-lay as well as after four, six and 12 weeks of cold storage, across multiple parameters. CSES determined that initial egg quality was not affected by hen housing type, whereas hen dietary nutritional changes did affect egg quality.

Through environmental and shell sampling, the prevalence of salmonella and campylobacter was found on collected samples from all three systems, with environmental dust levels influencing shell total aerobes. The forage area of the aviary system and scratch pads of the enriched colonies had the highest levels of total aerobes and coliforms, while eggs from the aviary floor had the highest total aerobes and coliform levels, CSES said.

Worker health, safety

Airborne PM inside hen houses, depending on its size, can make its way into workers' airways, with smaller particles being deposited deep into the lungs. Endotoxins (bacterial toxins) can promote airway irritation and inflammation, as well as decreased lung function.

Sampling from personal exposure monitors worn by workers while in the hen houses found that inhalable particle and PM2.5 concentrations, as well as endotoxins, were significantly higher in the aviary system compared to those in the conventional and enriched systems, which were not statistically different from each other, the coalition reported. It is believed that these levels were highest in the aviary system due to litter (dust-bathing material and manure) left on the floor.

Worker ergonomics were also considered, with a number of tasks standing out as possible risks, CSES said. Loading and unloading of cages in the conventional and enriched colony systems during population and de-population require extreme body positions, including squatting for an extended time. There was also significant twisting while "herding" the birds and standing on small diameter railings in these two systems.

The final analysis, which is scheduled for public release in March 2015, will explore interactions and tradeoffs between sustainability areas within each housing system.

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