Reducing concentrates supply level in Alpine dairy farms: a consequential-based LCA model

This study aimed to assess the consequences of reducing the concentrates supply level (CSL) in lactating cows’ diets on the carbon footprint of the north-eastern Alps dairy systems by adopting a consequential-based Life Cycle Assessment. Data originated from 40 dairy farms (31±21 livestock units - LU, 1.4±0.8 LU/ha, 21.0±5.5 kg fat- and protein-corrected milk – FPCM, and 4.5±2.8 kg DM concentrates per lactating cow/d). The impact category assessed was global warming potential (kg CO2-eq), without (GWP) and with (GWP_LUC) land-use change emissions. Three scenarios were tested: 100% (t0), 75% (t175) and 50% (t150) of the initial CSL, with a hay:concentrate substitution rate of 0.45:1 and milk yield (MY) modelled with regression analysis based on feed intake and ingredient composition. System expansion was used to handle the farm bodyweight coproduction and the consequences due to the change in milk provision level. Due to the cheesemaking destination of the alpine milk, a reduced availability of milk for mountain cheeses production has been considered. Functional units were 1 kg FPCM (farm level) and 1 kg of protein (CP; expanded system). Impact values at the farm and expanded system levels were analysed with GLM model that included CSL (3 classes: t0, t175, t150) as fixed effect, tested on the variance of the farm. From t0 to t175 and to t150, MY decreased by 10% and 20%, respectively. At t0, the production of 1 kg FPCM caused the emission of 1.06 kg (GWP) and 1.28 kg (GWP_LUC) CO2-eq. At the farm level, impact values increased by 2-5% at t175 and 5-12% at t150, with no significant differences with respect to t0. At t0, the production of 1 kg CP generated 32.1 kg (GWP) and 38.8 kg (GWP_LUC) CO2-eq. In the expanded system, the three scenarios of CSL did not affect the GWP and GWP_LUC values (+0-5%). In conclusion, the reduction in the CSL fed to lactating cows in Alpine dairy farms could favour the decoupling of the milk production from human-edible resources without worsening the related GWP but can also enhance the use of local resources and advance the resilience and sustainability of the local farming systems.