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Committee on a Framework for Assessing the Health, Environmental, and Social Effects of the Food System; Food and Nutrition Board; Board on Agriculture and Natural Resources; Institute of Medicine; National Research Council; Nesheim MC, Oria M, Yih PT, editors. A Framework for Assessing Effects of the Food System. Washington (DC): National Academies Press (US); 2015 Jun 17.
A Framework for Assessing Effects of the Food System.
Show detailsA Systems Approach to Exploring the Effects of Hen Housing
In contrast to the previous examples, in this annex the case study is based on an actual assessment, in which data on various dimensions of effects are being collected and analyzed for various hen housing alternatives. Interestingly, the planning, data collection, and analysis that occurred for this project closely parallel the principles and steps of this committee's framework.
This unique project allows simultaneous assessment of the magnitude of effects across all of the domains of effects of egg production on a commercial scale. This effort could not be assessed by conducting independent studies alone.
The project also is unique in bringing together a large group of stakeholders to share information and participate in evaluation and decision-making processes. The example shows the importance of involving a multidisciplinary team of researchers and other stakeholders from the beginning of the planning stages throughout the analysis step.
This project, however, does not address some dimensions of the committee's proposed framework, specifically distribution and resilience. These dimensions encompass economic effects that the policy intervention could have on farms of differing sizes. In addition, the project does not attempt to understand public attitudes toward farm animal welfare and the role that those attitudes played in consumer purchasing behavior or how an increase in the cost of eggs would affect consumer behavior. Significant knowledge gaps exist in this area.
The study illustrates the need to carefully choose alternative interventions for comparison. It shows that an intervention that might positively affect hen welfare, for example, also affects human health, the environment, and the economy of the sector.
The primary limitation of the project is that it is being conducted on a single farm, with one genetic strain of hens. This may constrain applicability to other U.S. regions and management practices, although the project will provide an overall framework and methodology for assessment that can be used across contexts. It should be noted that the goal of the project is to identify synergies and trade-offs, not to attempt to provide a formal integration of the data into an index that will “rank” the different housing systems. Each member stakeholder in the coalition can use the information obtained to make its own purchasing and supply decisions, based on its own organization's values with respect to sustainability.
Eggs are a primary source of animal protein worldwide. As early as in the 1950s, commercial egg producers began to adopt conventional cages to house laying hens. Before this intensification of egg production, hens were kept in small to medium-sized flocks in barns or in free-range systems. Although the latter allowed the hens to perform a wide range of natural behaviors, they also exposed them to diseases and predation. In addition, food safety concerns arose because hens could lay eggs outside their nesting areas (potentially allowing for contact with manure), and these eggs were soiled and dirtier than nest-laid eggs and potentially contaminated with manure-borne pathogens. Cage housing greatly reduced food safety issues because the birds' excreta fell through the cage floor and was removed by belt systems from the barn, thus preventing both birds and eggs from contacting manure. In general, cage flooring is sloped to allow eggs to roll out onto an egg collection belt. This prompt collection ensures improved cleanliness and freshness of the egg product. In general, cages facilitated the expansion and integration of the laying industry by allowing larger flock sizes and more automation of feeding, watering, and egg collection, which reduced the cost of eggs. Today, the vast majority of U.S. eggs (>95 percent) are from hens raised in conventional cage barns.
Starting in the 1960s, conventional cage housing began to be criticized, particularly in the European Union (EU), because it restricted the behavior of the hens and did not allow for the resources hens needed to perch, nest, or forage. In 1976, the Council of Europe published a convention stating that farm animals should be given “space appropriate to their physiological and ethological [behavioral] needs.” The European Union established minimum space standards for laying hens, and cages were entirely banned in 1999. In 2008, California voters passed a referendum named Proposition 2 (i.e., the Prevention of Farm Animal Cruelty Act) that, although ambiguously worded, effectively outlawed conventional cages for laying hens. Legislation that either outlawed or restricted the use of conventional cages was passed in Michigan, Ohio, Oregon, and Washington during the following 2 years.
After its ban on conventional cages for egg-laying hens, the European Union undertook considerable efforts to develop alternatives to conventional cage housing. The two alternative types of housing systems now acceptable under EU regulations are non-cage (also known as cage-free) systems, and furnished cages (also known in the United States as enriched colony systems). Non-cage systems include large buildings (i.e., aviaries) that provide indoor housing for tens or hundreds of thousands of hens that are allowed to move freely. The hens are provided with perches and nest boxes that largely allow for automated egg collection. A portion of the floor of the house contains bedding (e.g., wood shavings), which facilitates the pecking, scratching, and dustbathing behaviors of the hens. On the downside, this space also allows manure to accumulate over long time periods.
Several types of furnished cages exist, and in general they provide more space to birds than do conventional cages. Furnished cages, which each house a group of 20 to 60 hens, offer perches, a nest box, and an area on to which loose material is delivered to facilitate pecking, scratching, and dustbathing. As with conventional cages, the cage floor is made entirely of wire and is sloped so that the eggs roll out onto an automatic egg collection belt1 and the manure falls onto manure collection belts that remove waste from the building.
Identify the Problem
The first step of an assessment is to identify the problem. This is typically done based on consultation with stakeholders and reviews of relevant literature. The problem identified for this assessment is that changes in hen housing potentially have far-reaching economic consequences and may also have unintended consequences in the areas of environmental quality, human and animal health, and worker safety. The objective of the current study has been to learn about interconnections and trade-offs in various alternative poultry housing configurations. Results of the current study may be used to inform public policy related to practices and management of egg-laying hens in the United States.
Define the Scope of the Problem and Identify the Scenarios
Once a problem has been identified, the next steps of an assessment are to frame its scope and to identify alternative scenarios. Framing the scope is done by characterizing the boundaries, components, processes, actors, and linkages encompassed by the system under consideration. Identifying alternative scenarios compares the performance of the current system—the baseline—with one or more alternative scenarios. This is done to understand the potential effects of a new policy or intervention under consideration. For this example, these two steps have been combined, and the scope of the problem and alternative scenarios are described by summarizing selected studies that have compared the effects of various hen housing systems.
Effects of Bans on Conventional Cage Systems
When the hen housing laws in the United States were passed, it became apparent that moving to alternative production systems would affect sustainability domains other than just hen health and welfare, including egg safety and quality, environmental quality, food affordability, worker health and safety, and public values and attitudes. In 2008, the American Egg Board2 funded Michigan State University and the University of California, Davis, to review existing knowledge in these sustainability areas and to identify gaps. A series of papers resulted that identified effects and knowledge gaps as discussed below. Significant knowledge gaps exist in understanding the public attitudes and values toward farm animal welfare. This area will be the subject of future studies and it is not listed below.
Hen health and welfare This area has been more intensively studied than any of the other sustainability areas (Lay et al., 2011). Conventional cages restrict hen behavior the most, whereas non-cage systems provide more space for movement and provide behavioral resources, with furnished cages being intermediate. However, non-cage systems are known to be more associated with hen health problems than are cage systems. These problems include higher risks of infection with diseases and parasites and higher rates of bone breakage due to hens' contact with manure and vectors. Incidences of cannibalism and pecking also are more abundant in non-cage versus cage systems. These factors are important drivers of mortality, which is often higher in non-cage than in cage systems.
Egg safety and quality Although a number of European studies have characterized egg quality in different hen housing systems, results have been contradictory with respect to attributes, such as egg size, shell strength, shell quality and integrity, egg interior quality, and egg nutritional quality (Holt et al., 2011). The major egg safety factor is Salmonella enteriditis contamination. When eggs are laid on top of manure or soil (which is often the case in cage-free systems), they become soiled with manure, and fecal pathogens on the shell can enter the egg through the egg pores. However, little conclusive research has been conducted on the effects of various housing systems on Salmonella.
Environmental quality Environmental impacts of laying hen production systems include air quality (particulate matter and ammonia), water quality (run-off), manure management (due to effects on ammonia production), and resource usage (feed, energy, land) (Xin et al., 2011). In general, particulate matter is lower in cage versus non-cage systems because the barns contain no manure that can be aerosolized. Manure is a primary contributor to higher ammonia concentrations in cage-free houses because it is generally not removed until the end of the laying cycle. Hens are stocked at lower density in furnished cages than in conventional cages, and at even lower density in non-cage systems. These lower densities are associated with greater land use and more feed consumption, thus contributing to reduced resource usage efficiency and a higher carbon footprint. Knowledge gaps included comparisons of environmental effects and footprints among the different hen housing systems in the United States, lack of process-based models for air emissions, lack of knowledge about the effectiveness of mitigation strategies, and limited understanding of interactions among environmental effects, worker safety, and hen health and welfare.
Food affordability Studies from Europe have shown that the cost of producing eggs was higher in non-cage versus cage systems, with costs of production in furnished cage systems intermediate. Data from California producers indicated that the shift from conventional cages to indoor non-cage systems would cause farm-level cost increases of about 40 percent per dozen eggs, but no U.S. data were available for furnished cages (Sumner et al., 2011). Gaps in knowledge include those related to costs of production in alternative production systems in the United States, impacts on smaller producers of having to make significant capital investments to adopt new housing systems, and the effects of increased egg prices on retailer and consumer behavior.
Worker health and safety Little information is available on worker health and safety issues associated with alternative production systems. Although it can be assumed that factors which affect hen health and comfort (e.g., dust, ammonia) also potentially affect workers, a lack of empirical information exists about the impacts of either environmental factors or ergonomic challenges.
Conduct the Analysis
The review conducted in this project to define the scope of the problem and identify alternative scenarios provided justification for the data collection, metrics, and analysis proposed by the stakeholder team assembled to assess this problem. The goal of their analysis was to outline trade-offs and ramifications of potential hen housing decisions.
This analysis provides an excellent example of a series of challenges within a major food production area. Decisions about the weight or importance of every major effect depend on reconciling competing value judgments. For example, is behavioral freedom more or less important than hen health as a consideration when deciding which housing system is more sustainable? To what extent do the magnitudes of each effect and the potential costs of mitigation affect decision making about hen welfare? Competing value judgments again come into play when weighing the importance of one area of sustainability against another when the information is conflicting. Various integration methods have been employed to address these challenges, including deliberative approaches, informal decision making, and quantitative analyses. The latter are appealing because they result in the assignment of numerical outcomes to the various sustainability attributes. However, because no empirically or logically “correct” way exists to assign such numbers, ultimately they also depend on value judgments. Participatory decision-making strategies that involve a broad array of stakeholders are a promising method for value integration, and a group of stakeholders was convened to begin this process for sustainable egg production.
Stakeholder Participation
The data gaps and approaches identified above 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), described by Swanson et al. (in press). CSES is a multi-stakeholder group collaborating on a study of housing alternatives for egg-laying hens in the United States. It has more than 30 members, including research institutions, trade organizations, scientific societies, nongovernmental organizations, egg suppliers, food manufacturers, and restaurant/retail/food service companies. Leadership for the project is provided by McDonald's, Cargill, Michigan State University, the University of California, Davis, and the American Humane Association, with the American Veterinary Medical Association, the U.S. Department of Agriculture's Agricultural Research Service, and the Environmental Defense Fund serving as advisors. Retailers have assumed a central role in discussions about animal welfare and the sustainability of the food supply in general because they have been increasingly subject to public activity (e.g., shareholders' resolutions, advertising campaigns) designed to influence their purchasing practices. CSES is facilitated by the Center for Food Integrity (CFI), a not-for-profit organization dedicated to building consumer trust and confidence in the food system. CFI members represent each segment of the food chain.
Metrics and Data Collection
The goal of CSES is 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 U.S. conditions. The data are being collected over two full hen flock cycles from a commercial farm in the Midwest that contains three types of housing facilities: conventional cage, cage-free aviary, and furnished cage systems.
The following effects/outcomes are being compared among the alternative hen housing systems:
- Hen health and welfare: Hen behavior and resource/space use, physiological indicators of stress, comprehensive physical condition, and health outcomes measured using a standardized evaluation system plus clinical observation and testing, bone quality, and bone-breaking strength (i.e., force required to break a bone).
- Egg safety and quality: Interior and exterior egg quality; egg shelf life; microbial contamination levels of eggs, egg-processing areas, and housing areas; immunological responses of hens to the Salmonella vaccine.
- Environmental quality: Indoor air quality and thermal conditions, gaseous and particulate emissions from houses and manure storage areas, efficiency of resource (feed, water, energy), nitrogen mass balance, life cycle analysis.
- Food affordability: Production costs (feed, land and buildings, labor, hen disease and health costs, pullet costs) and revenue (marketable output flows).
- Worker health and safety: Personnel exposure to gaseous and particulate matter, respiratory health, ergonomic stressors, musculoskeletal disorders.
The CSES provided more than $6.5 million for this research to be conducted, with additional significant costs incurred to construct or renovate the commercial houses to enable the project to be operated. In addition, CFI is conducting parallel research using focus groups to understand consumer attitudes toward hen housing systems and the sustainability of egg production, as well as to determine how those attitudes may be influenced when consumers are provided with the information obtained from the CSES research project.
REFERENCES
- Holt PS, Davies RH, Dewulf J, Gast RK, Huwe JK, Jones DR, Waltman D, Willian KR. The impact of different housing systems on egg safety and quality. Poultry Science. 2011;90(1):251–262. [PubMed: 21177467]
- Lay DC Jr., Fulton RM, Hester PY, Karcher DM, Kjaer JB, Mench JA, Mullens BA, Newberry RC, Nicol CJ, O'Sullivan NP, Porter RE. Hen welfare in different housing systems. Poultry Science. 2011;90(1):278–294. [PubMed: 21177469]
- Sumner DA, Gow H, Hayes D, Matthews W, Norwood B, Rosen-Molina JT, Thurman W. Economic and market issues on the sustainability of egg production in the United States: Analysis of alternative production systems. Poultry Science. 2011;90(1):241–250. [PubMed: 21177466]
- Swanson JC, Mench JA, Karcher D. Poultry Science. In press. The coalition for sustainable egg supply project: An introduction. [PMC free article: PMC4990887] [PubMed: 25737565]
- Xin H, Gates RS, Green AR, Mitloehner FM, Moore PA Jr., Wathes CM. Environmental impacts and sustainability of egg production systems. Poultry Science. 2011;90(1):263–277. [PubMed: 21177468]
Footnotes
- 1
Videos showing the features of different systems can be found at http://www2
.sustainableeggcoalition .org/resources (accessed January 20, 2015). - 2
The American Egg Board is the promotion, education, and research organization for the U.S. egg industry. It is composed of 18 members who are egg producers appointed by the Secretary of Agriculture to administer the program on behalf of all egg producers in the 48 contiguous states. The Board was authorized by the Egg Research and Consumer Information Act passed by the 93rd Congress and its activities are conducted under the oversight of the U.S. Department of Agriculture.
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