Environmental and economic assessment of year-round-grazing systems for Japanese Brown fattening steers

Abstract

The objectives of this study were to evaluate the environmental and economic impacts of year-round-grazing systems and a conventional housing system for Japanese Brown fattening steers by the life cycle assessment (LCA) method. Four treatments were designed in this study; grazing fattening without feed rice (G group), grazing fattening with feed rice (GR-1 and GR-2 groups) and conventional housing fattening (H group). For the three grazing groups (G, GR-1, GR-2), supplemental concentrate was constantly supplied and hay was supplied only in winter. The emissions from feed production, feed transportation, animal management, manure treatment and ruminal fermentation were assessed for the LCA. Impacts categories considered were energy consumption, global warming, acidification, and eutrophication. Impacts of NO₃ and P emissions from fertilizer and manure on eutrophication were included. The functional unit was set to be 1 kg of average daily gain. The impact of carbon sequestration from pasture was also considered. The result showed that environmental impacts of G group on global warming, acidification, and eutrophication were significantly higher than those of H group (P<0.05). Considering carbon sequestration in the pasture, the sensitivity analysis indicated that grazing systems could reduce substantive impact on global warming. For economic assessment, annual carcass sales of G group were significantly lower than those of H group (P<0.05) and annual production costs showed no significant difference among groups.