The aim of this experiment was to measure the enteric methane emissions in dairy cows fed diets rich in starch or sugar with and without manipulation of rumen pH. The rations were based on grass-clover silage supplemented with either wheat (W), NaOH treated wheat (WNaOH), sugar beet molasses (M) or sugar beet molasses with sodium bicarbonate (MBic). Wheat or molasses made up 35% of the ration dry matter (DM). Four cows were used in a 4 x 4 Latin square design. Emissions of methane and hydrogen were measured by means of open circuit indirect calorimetry on four consecutive days. The cows produced 32.1, 33.0, 35.9 and 34.7 l CH4 per kg DM on diet W, WNaOH, M and MBic, respectively. The emisson of CH4 per kg DM (P=0.03), and the daily hydrogen emission (P<0.001) were higher on molasses diets compared to the what diets. It is concluded that methane emisson is higher in sugar-rich than in starch-rich diets.
Emissions of Gas and Dust From Livestock, 2013, p. 206-208