Livestock farming plays a key role in the global food system, the economy, and the livelihood of millions of people. One of the undesirable facts in livestock production is the still insufficient consideration of the related environmental sustainability. Globally, livestock production accounts for about 14.5% of total greenhouse gas (GHG) emissions. These emissions are significantly changing our atmosphere and their impact is increasing. The main causes of these emissions are inefficient land resource management, synthetic fertilizer application, enteric fermentation, manure-related, and animal breed. It is, therefore, important to apply appropriate farm planning and management strategies to reduce the emissions. To support the global effort, we developed an application that we introduce in this paper, FarmMOODSS, to estimate net emissions by calculating GHG emissions at the farm level. FarmMOODSS recommends an optimized feeding program for emission mitigation. A multi-objective optimization algorithm is applied for feed optimization, including an IoT data mining function. The tool is developed based on a dairy farm use case.