In Holland a desk study of Alfa Accountants with 800 dairy farms shows that farms with the highest feed efficiency have the lowest CO2 emission per kilogram milk. The 25 percent farms with the highest feed efficiency of 1.29 kilogram dry matter per kilogram milk had an CO2 emission of 1205 CO2 equivalents per 100 kilogram milk. The 25 percent farms with the lowest feed efficiency of 1.00 kilogram dry matter per kilogram milk had an CO2 emission of 1422 CO2 equivalents per 100 kilogram milk.