| الوصف: |
The global livestock sector is rapidly transforming. Over the past few decades, many livestock systems over the world have evolved from local, small-scale mixed crop-livestock systems to global and demand-driven supply chains, in which feed and animal production stages are often disconnected. These changes, driven by economic opportunities, have altered the way livestock production impacts global nitrogen and phosphorus flows and emissions. These emissions take place in several stages of the supply chains, namely feed production, animal production and processing of animal products and threaten water, soil and air quality, but also climate, biodiversity and human health. Achieving better nutrient management is thus an important aspect of improving environmental performance in the livestock sector. Improving the efficiency of nutrient use has been identified as the main strategy to reduce environmental pressures while achieving global food security and sustainability. To reduce nutrient losses in livestock supply chains, there is a need for methods and indicators that determine these losses or the other way around, determine the nutrient use efficiency (NUE). Most studies that evaluate NUE focus on animal, farm or regional level. For global livestock supply chains, however, that run across national and continental boundaries, such approaches over-look nutrient losses associated with off-farm activities, such as the production of feed. Some studies assess nutrient losses and NUE at a chain level, but they do not consider the entire supply chain and do not consider the effect of nutrient recycling and stock changes on NUE, or do not identify hotspots of nutrient loss along the chain that are required to support targeted nutrient improvement pathways towards sustainable nutrient use. The two objectives of this thesis, therefore, were to develop a framework of indicators to assess nutrient flows and emissions along global livestock supply chains, while identifying data, which can be improved to enhance the accuracy of ... |
