Livestock systems are challenged because of their environmental impacts and in terms of animal welfare. A now classic vision of the transition of the agricultural sector is the substitution of conventional industrial systems by ecological or organic production systems. However, the benefits, difficulties and risks of such a massive substitution are not always evaluated and rationally discussed among actors. We developed scenarios towards 2050 for the livestock sector in Belgium. The objective was to provide actors with a shared framework for discussing transition horizons and conditions and challenges for entering transition pathways. The study provided an analysis of the current diversity of production systems in each livestock sector. Three scenarios were then described: a. a business-as-usual scenario; b. a scenario based on extensive systems and relying on national cereals production for livestock feeding; and c. a scenario exclusively based on organic systems and feed from byproducts. This research was funded by an environmental NGO. While the most alternative scenario (c) was chosen in compliance with the NGO's guidelines, the study also offered a reference scenario (a) and an intermediary scenario (b). The consequences of each scenario were assessed in terms of environmental aspects, production, export capacities and required changes in food habits. The study was rolled out with a participatory process: actors contributed to the data collection and then had the opportunity to collectively discuss the scenarios and their consequences. A peer-review was implemented in order to strengthen the reliability of the results. Finally, a public presentation of the study was organized and gathered about sixty participants. The responses of farmers' unions to the release of this study can be analyzed and provide insights on the understanding of such prospective approaches by actors. Several aspects were identified as critical for ensuring acceptance of the study as a relevant framework: 1. proactively offering ...