Effect of winter feeding systems on farm greenhouse gas emissions

Overwintering beef cows is a major cost in Canadian cow-calf production systems and swath grazing is a potential alternative to reduce winter feeding cost relative to the traditional drylot feeding systems. The objective was to estimate and compare greenhouse gas (GHG) emissions from winter feeding systems: i) swath grazing on triticale, ii) swath grazing on corn, and iii) conventional drylot feeding systems (control). Data were obtained from a study conducted over three production cycles (2008/2009, 2009/2010, 2010/2011) at the Lacombe Research Center in western Canada. Greenhouse gas emissions were estimated by calculating methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions from different sources using Intergovernmental Panel on Climate Change (IPCC) Tier 2 approach. Methane emissions were estimated from enteric fermentation and manure, N2O emissions from fertilization and manure, and CO2 emissions from energy use for farm activities related to feed production and processing, feed and bedding delivery and manure removal. Total emission expressed per kg of feed produced and fed were significantly (P<0.001) lower for both the swath grazing treatments relative to the control treatment. Emissions per cow varied among treatments (P<0.001), higher for control (12.3kg CO2e cow-d−1) than corn (9.4kg CO2e cow-d−1), with triticale (11.0kg CO2e cow-d−1) intermediate. In all the treatments, the largest fraction of emissions was enteric CH4 (69–76%), followed by N2O (14–24%). The contribution of energy-derived CO2 emissions for total GHG emissions was lower in swath grazing treatments (5–7%) compared to a traditional feeding system (11%) due to their minimal energy use. Farm activity related energy use was 9.4, 11.5 and 21.4MJ cow-d−1 for triticale, corn and conventional drylot feeding, respectively. This study indicated that swath grazing on triticale or corn can be an effective alternative winter feeding systems to reduce GHG emissions and increase energy use efficiency of Canadian beef cattle industry.