Life cycle assessment of grassland-based dairy production systems in Switzerland

The feeding system of dairy cows can strongly influence their environmental impacts. We compared three grassland-based production systems: (A) full-grazing with seasonal calving, and indoor feeding of fresh herbage with (B) reduced concentrate (<500 kg cow-1 yr-1), and (C) standard concentrate (800-1,200 kg cow-1 yr-1) supplementation. The three systems were analysed on 12 pilot farms (PF) (four per strategy) in 2014 as well as on the experimental farm (EF) of the centre for Nature and Nutrition in Hohenrain (2014-16) with the life cycle assessment (LCA) method Swiss Agricultural LCA (SALCA). In terms of environmental impacts, higher concentrate inputs (C) resulted in higher P and K resource use, deforestation and ecotoxicity per kilogram of energy corrected milk (kg ECM). Full grazing tended to a higher global warming potential per kg ECM. However, the differences in environmental impacts per kg ECM were often larger between the single PF and the years than between the three systems. Four main factors influencing the environmental impacts were identified: (1) composition of the feed ration, (2) performance of the system (feed conversion ratio), (3) grazing and manure management, (4) purchase of animals.