The simple statement that decreasing enteric methane emissions without affecting feed digestibility will increase the animals’ productivity or energy retention therefore appears to be inadequate. A further requirement would be that the reducing equivalents spared from methane production are incorporated in molecules that are limiting either bacterial or animal metabolic processes. The direct environmental impact of methane production from the dairy cows in this experiment was decreased; daily methane production was lowered by 58 g/cow per day, or 1.5 kg of CO2-equivalents/cow per day.