In the North-western mountains of Vietnam, erosion and loss of fertility of agricultural slopes land, and dry season forage deficit are the main constraints to the development of livestock production system. Forage production options seem relevant to jointly address these two constraints and promote an agroecological transition of mixed crop-livestock systems in the region. Forage production scenarios were designed with farmers and local authorities through interviews and their impacts on the farm sustainability evaluated using Tìm ra mô hình, a simulation tool adapted to the farms of the region. Data describing the structure and practices of farms were collected by farm surveys. The results show that co-designed scenarios can represent options for agroecological transition of farms. To be effective and implemented, these scenarios must be adapted to the farms types and accompanied by support actions.