PRELIMINARY RESULTS OF STUDY COMPARING EGG PRODUCTION SYSTEMS RELEASED
Aug. 19, 2014
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, CSES noted that the research assessed five areas of sustainability: animal health and well-being, environmental impact, food affordability, food safety and worker health and safety. A complete overview of the preliminary results is available here.
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 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.
The research assessed the environmental impact of each of the three systems, including the effect on 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 the 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 study period, in addition to 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 similar, CSES noted. The aviary system also had six to seven times the PM emissions of the other two systems. The higher PM levels and emissions were caused by hens performing activities on the litter floor, the coalition explained.
Energy use and costs were similar across all three systems, according to CSES. The aviary house required some supplemental heat (from propane) in the first flock, but not in the second flock. In all houses, operation of manure drying blowers accounted for 55-75% of total electricity use throughout different seasons.
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, it was 36% more expensive to produce eggs in the aviary system 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.
Eggs from each of the three systems were assessed for quality across multiple parameters at two days post-lay and after four, six and 12 weeks of cold storage. 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.
Hens from all housing systems shed salmonella at a high rate of between 89% and 100%. Also, the dry belt manure removal system impeded the detection of campylobacter as the manure was no longer a good environment for its detection.
It's important to note that management practices likely had the greatest influence on environmental and egg shell microbiology, CSES suggested.
Worker health, safety
Airborne PM inside hen houses, depending on the 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 PM 2.5 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 cages in the conventional and enriched colony systems during population and de-population required extreme body positions, including squatting for an extended period of time, as well as significant twisting while "herding" the birds and standing on small-diameter railings.
According to CSES, gathering the eggs birds had laid on the floor in the aviary system was found to be another issue for worker ergonomics as it warranted extreme body positions, including squatting for an extended period of time. Furthermore, extreme arm positions over the shoulder and reaching to the side, as well as rapid and extreme hand and wrist positions, were noted.
Crawling and lying on the floor to collect floor eggs also exposed employees to potential respiratory hazards - especially if no respiratory protection was worn - and to potential infection hazards to their hands and the knees, CSES said.
The final analysis, which is scheduled for public release in March 2015, will explore interactions and trade-offs between sustainability areas within each housing system.
CSES is a multi-stakeholder group that is collaborating on a commercial-scale study of housing alternatives for egg- laying hens in the U.S. This research and data collection were conducted on a commercial farm, with all three housing types at the same location.