SUPPLEMENTARY_DATA.docx

Most methane efficiency studies in dairy focus only on lactation, missing emissions from growth and dry periods. We used a lifetime modeling approach to evaluate how reducing dietary concentrate and extending ewe longevity affect total methane emissions relative to milk production in dairy sheep. We found that concentrate reduction had little effect on lifetime methane emissions per unit of milk of the ewe, but extending longevity significantly improved it. These results highlight the importance of lifetime-based metrics and show that increasing longevity is an effective climate strategy in low-input systems