As the EU moved toward implementation of the conventional cage ban, they invested heavily in the evaluation and development of alternative production systems, particularly focusing on hen welfare. However, it became apparent that there could potentially be other important effects on the sustainability of egg production related to moving to such systems, including effects on the environment, egg safety and quality, food affordability, and worker health and safety. In 2008 the American Egg Board provided funding to Michigan State University and the University of California-Davis to assemble teams of national and international experts from various sectors (mainly academia, but also government, industry, and non-government organizations) to review existing knowledge in these areas, and to highlight gaps.
An issue that spanned all sustainability areas was that most research had been carried out in Europe, and that there was a need to evaluate effects in the US, given differences in public attitudes, economic and labour structures, and various aspects of hen management (e.g. hen genetics, egg safety and environmental regulations, building design, etc). In addition, there was limited commercial-scale research upon which to draw conclusions, as well as a lack of research that studied various aspects of sustainability simultaneously and in an integrated fashion.
The data gaps and approaches identified were influential in informing the next stage in the process of evaluating the sustainability of egg production, which was the formation of the Coalition for a Sustainable Egg Supply (CSES; http://www2.sustainableeggcoalition.org/). The CSES is a multi-stakeholder group led by McDonald’s, Cargill, Michigan State University, University of California-Davis, and the American Humane Association, with the American Veterinary Medical Association, the USDA Agricultural Research Service, and the Environmental Defense Fund serving as advisors. The CSES has more than 30 members, which include research institutions, trade organizations, scientific societies, non-governmental organizations, egg suppliers, food manufacturers, and restaurant/retail/food service companies. The CSES is facilitated by the Center for Food Integrity, which is a not-for-profit organization dedicated to building consumer trust and confidence in the food system and whose members represent each segment of the food chain.
The goal of the CSES was to collect data to understand the magnitude of effects and the trade-offs in terms of hen welfare, worker health and safety, food affordability, environmental impacts, and egg safety and quality in different hen housing systems under US conditions. The data were collected over two full flock cycles from a commercial farm in the Midwest that contained three types of housing systems: conventional cage (CC), cage-free aviary (AV), and enriched colony (EC) (see below; and see the CSES website for a full description and pictures of the facility and systems).
Research teams were assembled from Michigan State University, University of California-Davis, Iowa State University, USDA-ARS, and Cargill.
The following sustainability effects/outcomes were evaluated by these teams:
Animal health and welfare
The assessment of hen health and welfare focused on evaluation of hen behavior, health, physical condition, bone quality (because hens develop osteoporosis, which can lead to bone breakage), and stress responses. Hens’ use of the perches, litter/scratch areas, feeders and nests in the EC and AV were characterized during early, mid- and late-lay via in person and video observation, to assess the adequacy of resource use in these two systems. Hens that died in all systems were periodically necropsied to evaluate health issues and determine causes of mortality. The physical condition of 100 hens per housing system was evaluated during early, mid- and late-lay using the Welfare Quality Assessment protocol (2009), which involves assessing eye, foot, and respiratory health; checking for parasites; evaluating keel bone problems (breaks and deviations, an increasingly common problem, especially in alternative production systems); and evaluating feather cover and feather cleanliness. At placement and end-of-lay, bone quality of the tibiae and humeri of 120 hens per system was assessed using biochemical, morphological and biomechanical techniques. To measure physiological stress, white blood cells were counted and adrenal glands weighed from selected hens in each system at pullet placement, peak, middle and end of lay.
Continuous environmental monitoring of all systems and their manure storage facility was carried out over both flock cycles using two state-of-the-art monitoring systems. In addition, feed samples were taken periodically to determine nutrient composition. Moreover, properties of the hen manure removed from the houses and the storage were monitored.
These measurements were used to evaluate:
1) house thermal environment;
2) house air environment (ammonia, carbon dioxide and particulate matter);
3) ammonia, particulate matter, and greenhouse gas emissions from the houses;
4) energy use;
5) nutrient flow in feed, eggs and manure;
6) moisture and nitrogen content of manure from the houses and manure storage bays as an indicator of fertilizer value and emissions potential.
In addition, models were developed for determining how air temperature distributions, ventilation rates and ammonia emissions would be affected by changes in stocking density.
Food safety and quality
Egg quality was evaluated during both flock cycles by collecting eggs from all housing systems quarterly. Various internal and external quality measures were assessed, including shell dynamic thickness, egg weight, static compression shell strength, albumin height/Haugh units, yolk index, static compression vitelline membrane strength and elasticity, and whole egg total solids. Similar quality measures were also taken from eggs that had been cold-stored for 4, 6 or 12 weeks, to determine whether egg quality decline in storage was affected by housing type. Egg safety was evaluated during the second flock cycle. Environmental samples were collected from the wire areas and manure scrapers in all three systems, and from the nest pads in the EC and AV, the litter in AV, and the scratch pad in EC. Egg shell pools were made from eggs laid on the wire in all three systems, from eggs laid in the nests in AV and EC, and from eggs laid in the litter in AV. The indicator populations of total aerobic organisms and coliforms were enumerated, and the prevalence (presence or absence) of Salmonella spp. and Campylobacter spp. determined. Last, Salmonella vaccination effectiveness in the three systems was assessed by evaluating hen immune response.
Worker health and safety
This portion of the project assessed worker respiratory health, ergonomic challenges, and workplace hazards in the three housing systems. For the respiratory health assessments, the workers wore backpacks with exposure monitors during their shifts that measured their exposure to ammonia, endotoxins and particulate matter. Their lung function and breathing symptoms both before and after their work shift were also assessed. Workers were observed carrying out various tasks during the day, and these were then classified indicating their level of ergonomic risk due to body position and the three ergonomic stressors of force, repetition and posture.
Farm managers provided specific cost of production data measured weekly, biweekly and monthly during commercial operations over the two flock cycles. These data were used to compare feed costs, labour costs, pullet costs, calculated energy costs, capital costs and miscellaneous operating costs and the sum of all available costs across the three housing systems.
(From Proceedings of the “Midwest Poultry Federation Convention”, St. Paul, Minnesota, U.S.A.)