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The world’s population and food consumption are increasing drastically while natural resources are decreasing. In particular, energy use is an important component of reaching sustainability in agricultural production processes because of its shortage as resource, its influence on air pollution and its role in the economics of production. This study used system modeling to examine interactions between crop and livestock procedures and between levels of different input factors and their effects on yields in order to determine agricultural energy intensity. A method based on direct and indirect energy inputs within the livestock operation and plant production is used. A sensitivity analysis is done to investigate the influence of site conditions on the energy intensity of milk production and to highlight recommendations for management practices in livestock operations to reduce the energy use on dairy farms in Germany. An uncertainty analysis is used to evaluate the results of this study. Plant production, which consists of feed-supply and diet composition, constitutes the main influence on energy intensity in dairy farming. The energy intensity of feed-supply is strongly dependent on the quality of land and its management. An increasing use of concentrate in the dairy diet leads to a higher energy intensity for the process. Livestock operation accounts for one third of the energy intensity in milk production. The rearing period of a heifer at a dairy farm requires an energy input of 13–16GJ. The share of the energy intensity of the rearing period of the heifer per kg of milk changes, depending on the service life of the dairy cow. The service life of the cow increases, while the share of the energy intensity of the process section replacement decreases. Noting the influence of the energy intensity of machines and technical facilities in dairy farming is useful for overall energy use reduction. Here, also, the pasture is shown as a possibility for reducing the fossil energy input on-farm. The animal houses influence the energy intensity only marginally. Based on the sensitivity analysis of farm management and land quality, the energy intensity varies between 3.0 and 3.6MJkg⁻¹ energy corrected milk for an average milk yield of 8000kg ECM cow⁻¹ year⁻¹. Increasing milk yields lead to a reduction of the energy intensity per kg ECM. But this effect is reduced with rising milk yields because of higher energy inputs needed for the feed-supply, due to a higher share of concentrate and a typically higher replacement rate for the herd.
