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

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.

KEYWORDS:

• Greenhouse gas emissions
• ecotoxicity
• eutrophication
• energy
• dairy farm systems

Acknowledgements

E. Darré did a graduate internship at the Department of Biometry and Statistics, Agronomy College, EEMAC, UDELAR, supervised by M. Cadenazzi for part of the analyses for this paper. The Departments of Environmental Systems and Livestock and Pasture Production from the Agronomy College–UDELAR, Uruguay, provided the infrastructure support. Authors thank Gabriel Bagnato and Ana Bianco from the Uruguayan National Institute of Milk (INALE) for sharing the survey data on dairy systems in Uruguay, as well as Albana Melognio and Amabelia del Pino for its technical and academic contributions to this research.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was funded by a doctoral fellowship to E. Llanos from the Universidad de la República Uruguay–Academic Graduate Commission (CAP-UDELAR) and a doctoral fellowship to E. Darré from the Agencia Nacional de Investigación e Innovación (ANII), both supervised by V. Picasso. E. Llanos was a visiting scholar at University of Wisconsin–Madison, Agronomy Department, while he worked on analyses for this paper.