“…Reducing the use of grain and its attendant CO 2 and N 2 O emissions, while maintaining economically sustainable levels of milk production, is contingent upon feeding highest forage quality, which is made possible through, for example, the use of best pasture management strategies. Since the N 2 O emission from manure may not be much different between confinement and pasture systems (Mosier et al, 1998), the main system difference in N 2 O emission is related to mineral nitrogen fertilizer use (Flessa et al, 2002;Snyder et al, 2009). Feeding supplemental corn, for example, adds to the total GHG emission through both the use of MNF (Refsgaard et al, 1998;Flessa et al, 2002), and tillage, where tillage increases emissions of GHGs (Robertson et al, 2000) compared with grazed pasture (Saggar et al, 2004).…”