Les ruminants laitiers sont-ils efficients dans l’utilisation des surfaces ? examines the efficiency of dairy ruminants in utilizing land surfaces. It finds that dairy ruminants are net producers of protein for human consumption, requiring around 0.5 kg of plant protein consumable by humans to produce 1 kg of animal protein for humans. However, it acknowledges the real competition for land usage and argues criteria around land area and nutritional quality need clarification to better evaluate sustainability. Preliminary results show variability depending on arable land used for animals and estimated long-term plant yields, leaving many questions still to be answered by ongoing work.