Updated project metadata. Ruminant livestock are one of the major contributors to carbon emission contributing the global warming issue. Methane (CH4) produced from enteric microbial fermentation of feed in the reticulo-rumen are known to differ between sheep with different digestive function and fermentation products such as metabolites. However, the molecular mechanism underpinning differences in methane emission remains to be fully elucidated. We extracted a membrane and cytosolic protein fraction of rumen epithelium proteins from both high (H) and low (L) CH4 emitting sheep. Protein abundance differences between the phenotypes were quantified using SWATH-mass spectrometry. We identified 92 proteins annotated as cell surface transporters, of which only solute carrier family (SLC) 40A1 had a greater fold change of protein expression in the high methane emission phenotype. The main difference in protein abundance we found were related to the metabolism of glucose, lactate and processes of cell defence against microbes in the epithelium of sheep in each group. To best of our knowledge, this represents one of the most comprehensive proteomes of ovine rumen epithelium to date.