Life cycle assessment of extended bale grazing as an overwintering strategy for reducing greenhouse gases from Western Canada beef production
Baseline life cycle GHG emissions associated with beef systems have been studied globally (e.g. Lupo et al. 2013; Ridoutt et al. 2011; Beauchemin et al. 2010; Nguyen et al. 2010; Casey and Holden 2006; Ogino et al., 2007), but only a few LCA studies have considered reducing emissions through changes in management practices or strategies, such as the effect of feeding length on GHGs (Ogino et al. 2004), the impact of managed pasture compared to feed-lot finishing beef production strategies in the Upper Midwestern United States (Pelletier et al. 2010), and the use of growth promotants in calf-fed and yearling-fed beef production systems (Basarab et al. 2012).
Canada, a leading beef-producing and exporting country, is trying to mitigate its greenhouse gas emissions (GHG) through cost-effective Beneficial Management Practices (BMPs). Cow-calf operations in Manitoba, Canada are increasingly using extended bale grazing (EBG) overwintering, as a cost-saving alternative to traditional dry lot (TDL) operations, where animals are bale-grazed in December, and confined from Jan 1 to May 15, requiring more labor and management. In EBG animals are only confined for 1 month (Mar 1-Mar 30) during calving, and bale-grazed for the remainder of the winter. However, EBG may require feed supplements to maintain weight under cold stress conditions. The goal of this life cycle assessment study was to determine GHG emissions to produce a 205 kg weaned calf and a 605 kg finished beef animal based on TDL and EBG strategies.
The net life cycle GHG emissions for TDL based systems were 6700 kg CO2e per finished animal (11.1 kg CO2e kg-1 live weight), including C sequestration in pasture and in hay production. There was a net GHG reduction of ~ 10 % for producing a weaned calf in the EBG scenarios relative to TDL operations, mostly due to differences in manure management in the two systems; however, there is a higher potential for nutrient runoff in the EBG system, where manure is left on the pasture/snow surface and subject to runoff during snowmelt, compared to the TDL system where manure is stockpiled and then spread on hay fields when conditions are less favorable for runoff.
There were challenges in determining changes in GHG emissions due to different management practices in beef production systems due to insufficient knowledge and data in emission factors related to nitrous oxide dynamics, and limited data on feed impacts on enteric emissions for different livestock categories. Additionally, there is high variability in GHG emissions associated with differences in C sequestration rates as found through the sensitivity analysis. More research is needed to understand these dynamics and environmental trade-offs in cow-calf systems. The development of a BMP based on EGB must consider these uncertainties and the many factors required for economically and environmentally sustainable cattle overwintering systems.
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