1. Introduction
Livestock production systems contribute 12–18% to the global
anthropogenic greenhouse gas (GHG) emissions in carbon dioxide
equivalents (CO2-eq) (Steinfeld et al., 2006; Westhoek et al., 2011).
The direct methane and nitrous oxide emissions from enteric fermentation
and manure management practices (including manure
application) contribute 5.4 Gt CO2-eq GHG to the global emissions
annually (FAO, 2013). Enteric methane emission is the largest
source of GHG from agriculture. This contribution will likely