Do pasture-based mixed dairy systems with higher milk production have lower environmental impacts? A Uruguayan case study

Abstract

ABSTRACT The increased milk production of pastured-based mixed dairy systems has involved higher use of concentrates and inputs, which led to increased environmental impacts. Usually these impacts are expressed per unit of product, which does not reflect the local impact per unit of land. The objective of this paper was to estimate global and local environmental impacts per kg of milk and per hectare. Fossil energy use, greenhouse gas emissions, water ecotoxicity, nutrient aquatic eutrophication potential, and integrated standardised indices of environmental impacts (IEI) were estimated for 277 pastured-based dairy systems in Uruguay, clustered in seven milk production groups. Dairy systems with higher milk production had lower greenhouse gas emissions but higher ecotoxicity per kg of milk than systems with lower milk production, and the integrated index did not change. In contrast, all the individual indicators and the integrated indices per hectare were higher for the higher milk production systems. The results suggest that increasing milk productivity did not reduce environmental impacts per kg, and increased impacts per ha. Management factors including type of diet (pasture vs concentrate), amount of inputs, and type of grazing system may be more relevant in determining environmental impacts of dairy systems than productivity per se.