Pasture quality and greenhouse gases

PASTURE QUALITY HAS a significant and direct effect on the greenhouse gas (GHG) footprint of grazing livestock in New Zealand. The GHGs of importance are methane (CH4), due to fermentation of feed in the rumen(39), and nitrous oxide (N2O), resulting from urine deposition(40). Two fundamental feed quality principles are at play. The first is energy density (megajoules of metabolisable energy per kg of dry matter (MJME/kg DM)) and nitrogen (N) concentration (g N/kg DM). GHG emissions therefore are directly related to animal intake. The second is feed quality — as it decreases, CH4 emissions increase(41), whereas N2O emissions can decrease because total urinary N deposited decreases(42)