Cows (https://www.economist.com/international/2024/12/12/what-has-four-stomachs-and-could-change-the-world?utm_campaign=a.io&utm_medium=audio.podcast.np&utm_source=theintelligence&utm_content=discovery.content.anonymous.tr_shownotes_na-na_article&utm_term=sa.listeners) produce far more milk in rich countries than in poor ones. Our correspondent explains how beefing up bovine productivity could feed more people and reduce planet-heating emissions. Why Spain is the best-performing rich-world