Environmental impact assessment of different cropping systems of home-grown feed for milk production

Animal feeding is a critical point in terms of both production efficiency and environmental impact for the livestock sector and farmer choices about home-grown feed can have great influence on environmental impact of milk production. The aim of the study was to assess the environmental performances of the most common home-grown fodder crops in Northern Italy and to analyse the impacts of different cropping system scenarios for milk production, through a Life Cycle Assessment (LCA) approach. The environmental impact of the most common home-grown feeds was calculated from cradle-to-the-animal's mouth expressing the different categories per hectare and per unit of net energy for lactation and protein digested in the small intestine when rumen-fermentable nitrogen is the limiting factor (PDIN). Moreover four scenarios (BASE, HAY, SILAGE, PROTEIN) characterized by different cropping systems were hypothesized to assess the environmental impact of milk production from cradle to farm gate in an intensive farming system. Primary data were collected by direct interviews in 134 dairy farms located in Lombardy Region (Northern Italy).Among the most common fodder crops grown in Northern Italy, alfalfa preserved as silage and, although with a lesser extent, the double cropping system "whole plant maize silage-Italian ryegrass hay" showed the best environmental performances especially when the impact are expressed per unit of net energy for lactation or digestible protein in the intestine. Alfalfa showed also the lowest values of acidification and eutrophication when they were expressed as unit of land. The high variability of forage quality suggests a great room for improvement in terms of mitigation potentials.The analysis of alternative cropping system scenarios for milk production showed that the cropping system based on alfalfa and grass hays (HAY scenario) had the lowest self-sufficiency in terms of DM and the highest values of all impact categories per kg of fat and protein corrected milk (FPCM). The PROTEIN scenario, characterized by the introduction in the cropping system of protein rich crops (whole plant soy silage and alfalfa hay) can be considered the best one in a global perspective. In fact, the PROTEIN scenario showed the lowest potentials for acidification, eutrophication and non-renewable fossil energy use per kg FPCM and a reasonable value in terms of GWP. Moreover, the PROTEIN scenario had the higher feed self-sufficiency in terms of both DM and CP. Thanks to their capability to fix atmospheric nitrogen increasing the cultivation of legume such as alfalfa and soy in the cropping system of Northern Italy can reduce the utilization of chemical nitrogen fertilization and, consequently, the environmental impact. Moreover, considering that the main part of soybean consumed in Italy is cultivated in South America, a higher farm self-sufficiency in terms of protein feeds could decrease the emissions of CO2 linked to land use change generated by the cultivation of soybean.