The context of agricultural production, climate change in particular, is increasingly requiring adaptations in the structure and management of farming systems. As explorers, implementers, testers and promoters of such adaptations, farmers and extension services have to be involved in the design process of adapted farming systems. However, the complexity of most design approaches produced by research (e.g. computer-model-based) keeps them outside the core of this process. Here we present a game called "forage rummy" developed to engage farmers and extension services in being the main players in livestock system design and evaluation. It relies on a number of "boundary objects" developed upon the conversion of scientific knowledge into more usable forms of support. These are a player-friendly game board based on a conceptual model of a livestock system on which flattened wooden sticks marked with year-round forage production and animal feeding requirements have to be assembled with the support of a computerized support system. Playing the game thus consists of repeated cycles of design of livestock systems adapted to scenarios of the agricultural production context and evaluation of their biophysical and organizational feasibility. An application to designing dairy systems adapted to climate change by 2050 is presented. As the first example of a game-based approach for farming system design, forage rummy proves to be useful in stimulating discussion, reflective and interactive analysis and learning about farming systems, their management and the scope for their adaptation. This is attributed to the researchers' effort to offer transparent and easily-usable forms of support to the design process. We conclude that the learning stimulated by the game could potentially lead to more consistent and concerted action between researchers, extension services and farmers.