The multiple objectives (i.e., productivity, efficiency, resilience, animal and consumer health, environmental protection, product quality) to which ruminant diets must respond require forages, feeds and diets to be characterized in more detail than has been done to date. RUMI-FEED therefore aims to provide knowledge, 3R(Replace, Reduce, Refine) - compliant methods, and reference data for the holistic assessment of forage and feed quality in herbage-based ruminant husbandry systems, in order to enable diet optimization to meet the multiple objectives of ruminant diets, with the ultimate aim of developing resource-efficient, site-adapted, low-input and sustainable ruminant husbandry systems in line with the principles of agroecology.