The document discusses the efficiency of dairy ruminants in utilizing land areas. It notes that while ruminants consume a large amount of plant proteins and energy, a significant portion of what they consume is not edible by humans. Studies show that dairy systems are net producers of proteins for human consumption, requiring only around 0.5 kg of plant proteins edible by humans to produce 1 kg of animal proteins for humans. However, ruminants do utilize agricultural lands, with around 29% of French agricultural area currently used for animal feed that could potentially be used to directly produce plant proteins for humans. More research is needed to fully evaluate the sustainability of dairy ruminant systems using a multi-criteria approach.