The increasingly stringent conditions underlying Swiss dairy production demand sustainable milk production systems that are economically optimized but also meet the ecological requirements of society. To determine such systems, a comparative-static LP model was constructed at farm level. Realistic production systems are reproduced in the model by means of binary variables. An Life Cycle Assessment (LCA) was integrated into the model to determine the environmental impacts of the farm. To this effect, the internal farm influences on production are illustrated in detail. An initial application of the model, in which a comparison of different income-optimized production systems was carried out, revealed some goal conflicts between economics and ecology. Systems involving full-time grazing achieved the best results in both aspects.