CONTEXT Pig production systems are currently in decline in the French Massif Central, while herbivore production systems, most of which are specialised, generate little income. The diversification of herbivore farms with pig production appears to be an interesting lever for improving farm sustainability. OBJECTIVE The objective of this study was to assess the impacts of adding pig production on the sustainability of beef and dairy farms and to assess the pros and cons of a DEA based multicriteria evaluation model. METHODS The Orfee bioeconomic model was used to simulate 17 beef or dairy farms with and without pigs. This pig production system consists of either a farrow-to-finish sow production system or a pig fattening production system only. The structural and technical parameters of these farms were established from a farm survey. Farm sustainability was assessed using 17 indicators. These indicators were hierarchically aggregated into a single sustainability composite indicator using an innovative method, the constrained directional benefit of the doubt (D-BoD) method. RESULTS AND CONCLUSIONS The results indicate that the addition of a pig production system has an overall positive impact on the sustainability of cattle farms. Mixed cattle-pig systems score significantly better on the social dimension as they generate more jobs and contribute more to food security. The overall economic performance is not significantly better than that of specialized systems for the price context from 2012 to 2022. The pig production system increases the average income per work unit for cattle farms but needs more purchased inputs to produce. This reduces but not offsets the risk reduction advantage of diversification and reduces production efficiency. Mixed farms do not score higher than specialized cattle farms on the environmental dimension. Mixed farms contribute less to global warming per kg of protein produced but have higher nitrogen and phosphorus surpluses. The constrained D-BoD method is a useful tool for endogenously aggregating indicators without having to arbitrarily set weights and thresholds to evaluate performance, but with certain limitations, such as the possibility that a farm may be judged efficient if it performs better on some indicators while being relatively weak on others. SIGNIFICANCE Favouring mixed farming appears to be an interesting lever for territorial development, but with two important issues: local supply of pig feed at a secure price and improved manure management to allow a virtuous cycle of nutrients.