The rumen is a major the site of digestion and absorption of energy predominantly in the form of short chain fatty acids as well as amino acids and simple carbohydrates. The research sought to determine if diets high or low in ME were associated with quantitative changes in the membrane bound proteins that transport and metabolise nutrients in the rumen epithelium (RE). The comprehensive assignment of proteins (>4000) to cellular location and quantification of differences in protein abundance will progress the annotation and understanding of protein functions in the ruminant genomes.