Winter feeding systems and farm greenhouse gas emissions

Abstract Text:

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 (12.3 kg CO₂e cow-d^-1) than corn (9.4 kg CO₂e cow-d^-1), with triticale (11.0 kg 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 21.4 MJ 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.

Keywords: Greenhouse gas, Swath grazing, Winter feeding