How to house a hen : assessing sustainable development of egg production systems

The objective of this study was to further develop and apply a methodology to assess the contribution of animal production systems to sustainable development (SusD). The practical use of the methodology is tested in a case study on egg production systems, because of the upcoming ban on the battery-cage system in 2012. This ban forces farmers to change to an alternative, more animal-friendly production system in the near future. Due to the general use of the term SusD, it is necessary to first define SusD in broad terms, before one can come to a more precise and context specific definition. In order to define SusD, two core elements have been identified. The first element is that SusD is not a fixed state of harmony, but rather a process of change, consistent with future as well as with present needs. The second element is that SusD relates to economic, ecological, and societal (EES) issues. Assessment of the contribution of animal production systems to SusD implies four steps: (1) description of the situation; (2) identification and definition of relevant EES issues; (3) selection and quantification of suitable sustainability indicators (SI); and (4) final assessment of the contribution to SusD. Selected EES issues included animal health and welfare, environment, egg quality, ergonomics, economics, consumer concerns, and knowledge and innovation. We compared four egg production systems, characterized by different housing systems, which were most common in the Netherlands: the battery-cage system, the deep-litter system with and without outdoor run, and the aviary system with outdoor run. We showed that on-farm quantification of SI was an appropriate method to identify strengths and weaknesses of different systems, and the variation within these systems as well. From this analysis it appeared that, within the boundaries of this study, the aviary system with outdoor run was the best alternative for the battery-cage system. The aviary system performed better on animal welfare and economics, but worse on environmental impact. No significant differences were found for other SI. Deep litter with and without outdoor run performed equally or worse than aviary with outdoor run on all SI. Many decisions during the four-step methodology, e.g., decisions on which stakeholders to involve, which reference values to choose, or how to aggregate information, are based on implicit value judgements. These value judgements influence the final results of the assessment, which makes it important to elucidate them when applying this methodology. Different users require a different level of aggregation and there is not a generally accepted way to aggregate SI results into a final index of SusD. The feature of SusD that it is context specific with regard to time and space, also contributes to the diversity of possible results. When presenting final results, therefore, the whole process has to be taken into account, which means that all choices have to be explicated.