A first-of-its-kind, commercial-scale study of housing alternatives for egg laying hens in North America has found no demonstrated presence of acute or chronic bird stress with any of the three housing systems studied.
From an overall bird mortality standpoint, death from hypocalcemia was more common in the aviary than conventional cages or enriched colonies, and aviary hens were more likely to die from being caught in the system, cannibalized or pecked extensively than were conventional cage or enriched colony hens.
Egg production through the first half of the flock cycles for each system was found to be fairly similar, with production from the aviary declining most through the remainder of the cycle. Average hen day production in the conventional cages was 3.5 to 4.8% less than the enriched colony, while the aviary was 4.3 to 6.7% less than the enriched colony system for the two flocks, respectively.
The Coalition for Sustainable Egg Supply (CSES), a multi-stakeholder group which collaborated on the Laying Hen Housing Research Project, said the goal of the research was to understand the sustainability impacts of three laying hen housing systems – cage-free aviary, enriched colony and conventional cage. It was also aimed at providing meaningful science-based data by which to help guide future egg production and purchasing decisions.
“This research represents a snapshot in time – it assesses elements of hen housing and egg production using a single hen breed/strain, in a particular region of the U.S., over the course of three years and two flocks, in these particular housing systems. While it highlights the trade-offs involved and can assist in supporting informed decision-making, caution should be exercised in applying the research results to other scenarios with different variables,” said CSES of the research results released March 18.
Specifically, the research assessed five areas of sustainability - animal health and well-being, food safety and quality, environmental impact, worker health and safety and food affordability.
"Before CSES, commercial-scale research evaluating the different aspects of the sustainability of hen housing systems was lacking and a more holistic, integrative approach was necessary,” said Dr. Janice Swanson, CSES co-scientific director, and professor of animal science at Michigan State University. “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 research found there are positive and negative impacts and trade-offs associated with each of the three hen housing systems. Depending on the goals and perspectives of a food production company, egg producer, or other food system stakeholder, those trade-offs may be weighed differently,” added Dr. Joy Mench, CSES co-scientific director, and professor of animal science at the University of California, Davis.
Among other findings, the research showed that pullets reared in the aviary had better skeletal integrity than those reared in the conventional system. Hens in the aviary and enriched colonies had a higher incidence of keel bone deviations and/or fractures than hens in the conventional cage system. Conversely, hens in conventional cages 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 cages or enriched colonies. Hens in the conventional cages and enriched colonies had cleaner feathers but worse feather cover than those in the aviary. Patterns of feather loss suggested that hens in conventional cages and enriched colonies lost feathers due mainly to abrasion against the cage, while those in aviary lost feathers due to aggressive pecking from other birds. Hens with large areas of feather loss would be expected to lose more body heat than better-feathered hens.
All of the resources (perches, scratch pad, nests) in the enriched colony were used, but the perches and nests were overall better-used than the scratch pad. There was consistent low use of the perches during the day and high use at night. Use of the scratch pad for foraging and dust bathing was low, but hens did sit, stand and sleep on the pad. Use of the nest was high, with approximately 97% of eggs laid there. Nest pads stayed clean. However, eggs that were not laid in the nest were usually laid on the scratch pad, which was found to become covered with manure over time.
Resources in the aviary were also well-used. Nest use was recorded in Flock 2 when hens were 19-36 weeks of age, and hens were found to lay their eggs in the nest approximately 97% of the time. At other times, however, there were periodic problems with eggs laid outside of nests, either on the floor in the litter or in other areas of the tiered enclosure. As in the enriched colony, the nest pads stayed clean. Hens used the internal perches extensively during the night and particularly the perches in the top level. Hens used the open litter area to dust bathe most often in either afternoon or late morning.
The research found that the hens were typically spread fairly evenly across the litter area, but were also seen to cluster there in large groups, with these ‘piles’ sometimes including as many as 229 hens and lasting for as long as six hours. Analysis of hen flight and landing success in the open litter area showed that failed landings were observed for 9.1-21% of flights, which could have contributed to the higher rates of keel breakage seen during the necropsies of aviary hens, since most failed landings were due to collisions with other hens.
Pullets were in good physical condition when they were placed regardless of whether they had been reared in an aviary or conventional pullet rearing system. Those reared in the aviary did have more keel abnormalities and dirtier feathers than conventionally-reared pullets, but also better foot condition as shown by less toe damage and shorter claws. For hens evaluated at 52 and 72 weeks of age, the conventional cage and aviary systems each had positive and negative effects on hen physical condition (e.g., a greater incidence of foot problems in conventional cages but foot problems most severe in the aviary; dirtier feathers in the aviary but largest amount of feather loss in conventional cages; highest incidence of keel abnormality in the aviary), with enriched colonies generally intermediate, the research found.
The tibiae and humeri of aviary-reared pullets had better loadbearing capacity and were stiffer than those of conventionally reared pullets, indicating better bone quality and less susceptibility to bone breakage. This better bone quality was maintained in aviary hens through 72 weeks. Bone quality of the tibiae and humeri was generally better in enriched colonies than in conventional cages at 72 weeks, although it was found to not be as good as in the aviary.
The main causes of mortality in all housing systems were hypocalcemia (low blood calcium levels) and egg yolk peritonitis (due to leakage of egg yolk into the abdominal cavity). Hypocalcemia was greatest in the aviary, with more than three times more hens affected in the aviary than in conventional cages and enriched colonies. Egg yolk peritonitis was greatest in the conventional cage house in Flock 1 while the aviary and enriched colony houses had equal numbers. For Flock 2, the conventional cage house and aviary house had equal numbers of egg yolk peritonitis while the enriched colony house had fewer birds with this condition. The aviary had the most hens that died from being caught in the structure.
Hens in all housing systems shed Salmonella spp. at a similar rate; the prevalence of Salmonella spp. associated with egg shells was very low and did not differ between systems. Daily mean indoor ammonia concentrations, particulate matter (dust) levels and particulate matter emissions were all highest in the aviary house and lowest in conventional and enriched colony houses.
Worker ergonomics were also considered, with tasks classified into three categories indicating their level of ergonomic risk due to body position during a specific task. Researchers also looked for three main ergonomic stressors, including force, repetition and posture. In the ergonomic review, a number of tasks stood out as possible risks. Loading and unloading of cages in the conventional cage and enriched colony houses during population and de-population required 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 houses. Gathering eggs that had been laid on the floor in the aviary house was also noted as an issue, as it warranted extreme body positions, including squatting for an extended period of time.
Further, 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 exposes the employees to potential respiratory hazards, especially if no respiratory protection is worn, as well as to potential infection hazards to the hands and the knees.
At 10% interest and depreciation, the aviary system had total capital costs per dozen eggs that were 179% higher than the conventional cage system, while the enriched colony system had total capital costs per dozen eggs that were 106% higher than conventional cage. The aviary system had total operating costs per dozen eggs that were 23% higher than the conventional system, while the enriched system had total operating costs per dozen eggs that were 4% higher than conventional. The aviary system had total costs per dozen eggs that were 36% higher than the conventional system, while the enriched system had total costs per dozen eggs that were 13% higher than conventional. Feed comprised the largest share of operating costs for each of the housing systems. While feed consumption per hen was similar across the systems, it increased over the life of the flock and was more costly per dozen eggs produced in the aviary system because production per living hen in that system declined more over the life of the flock than in other systems.
Overall operating costs per dozen were substantially higher for the aviary system and only slightly higher for the enriched colony system compared to the conventional cage system. Capital costs per dozen were much higher for aviary and enriched colony systems than the conventional cage system because of the costs associated with construction of those barns and the relatively few hens housed in each, compared to the conventional housing.
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 cage system, while the enriched colony system was 13% more expensive than conventional cage, primarily due to capital costs per dozen.
“When animals are involved, evaluating their welfare is a crucial aspect of any production system,” says Dr. Marion Garcia, chief veterinary officer and director of the Animal Welfare Research Institute, American Humane Association. “But to truly achieve sustainability, a variety of other factors such as the environment, the health and safety of the workers, food safety and quality, and affordability of what’s produced should also be considered, effectively evaluating the entire system.”
The results show the three systems researched each have associated trade-offs across those elements of sustainability. A complete research report and other research insights exploring the trade-offs associated with each system can be found at www.sustainableeggcoalition.org/final-results.
Interactive Infographic of research findings: http://www2.sustainableeggcoalition.org/research-results/