For promoting food system’s sustainability, it is paramount to study the trade-offs related to livestock system, considering food provision, emissions and land use, with a systemic approach. Livestock diet connects livestock performance with land use. We focus on cattle dietary composition (i.e. dry matter content, digestibility and gross energy content) and develop a model to explore the trade-offs among animal production (measured as total weight gain), methane emissions and land use impact indicators. Body growth is modelled through a metabolism approach based on energy balance. Methane emission is estimated using the IPCC tier 2 approach. This building block is integrated into a territorial-scale model in order to calculate a feed-food competition indicator and feed import needs, as indicators of impacts on land use. We simulated two scenarios in a grassland-dominated case study region, Bocage Bourbonnais (France), considering two events that might affect cattle diet characteristics: (1) drought and (2) pasture quality improvement. (1) is simulated by decreasing average yield (-10%) and dry matter content (-20%) of crops and grass, the grazing time on pasture (-20%) and cattle grass intake (-20%). To reach the same daily energy intake from the diet, the ratio of concentrates was increased. The results showed an increase in total weight gain (+6.3%), however with an increase in methane emission (+4.1%), feed-food competition (+1.7%) and considerable feed importation (+54.8%) compared to baseline. (2) was simulated by increasing both grass digestibility and gross energy content by 2%. Results showed that total weight gain increased by 2.6% while methane emission decreased by 1.9% and feed-food competition decreased by 2.5%, with no additional impact on feed importation. Our findings indicate that trade-offs exist in livestock system and diet composition is a lever to handle trade-offs related to livestock performance and land use. Relevant practices on pasture can provide a win-win opportunity on integrated cattle management of production, emission and land use.