**Background:** Beef production faces pressure to reduce greenhouse gas emissions and competition with human food systems. The SustainBeef project aimed to co-define and evaluate sustainable beef farming systems based on resources not edible by humans. Two innovations—fast rotational grazing (FRG) and crossbreeding—were identified by farmers and advisors as particularly relevant. This study used the FarmDyn bio-economic model to assess these innovations across three European beef production systems.
**Methods:** The analysis was performed from cradle to farm gate using 2017 data from representative farms in Belgium, France, Italy, and Germany. Three systems were modeled: (1) a Belgian system with a Belgian Blue suckler cow breeder and a separate fattener farm; (2) a French-Italian system with Charolais/Salers suckler cows in the Massif Central fattened in Veneto, Italy; and (3) a German integrated dairy-crop farm fattening its own Holstein male calves. Two scenarios were tested against baselines: FRG alone (improved pasture management with 0.5–3 day rotations) and system redesign (SR) combining FRG with crossbreeding. In the Belgian SR, the system shifted to a growing-fattening farm supplied with Belgian Blue × Holstein crossbred calves from a dairy herd. In the French SR, Charolais cows were inseminated with Angus, and fattening occurred on the breeding farm. In the German SR, Holstein cows were inseminated with Belgian Blue sexed semen. FRG increased yearly dry matter yield to 9.0 t/ha (BE), 4.4 t/ha (FR), and 9.9 t/ha (GE) vs. 8.0, 4.0, and 9.0 t/ha at baseline. Work time for pasturing increased by 10%, and variable costs increased by EUR 37.5/ha. Sustainability indicators included global warming potential (GWP) using ReCiPe methodology, work time, farm profit, and net human-edible protein (HEP) efficiency. A global sensitivity analysis varied stable size (±20%), grassland yields (±10%), and slaughter age (±10%) using Latin Hypercube Sampling with 100 draws.
**Key Results:** FRG alone had marginal effects on GWP (<±2%). In BE, GWP improved by 1% (−0.3 kg CO₂eq/kg beef), profit increased by 5%, work time increased by 17.5% (1.10 min/kg carcass), and net HEP efficiency rose to 0.69 (+3%). In FR-IT, GWP increased by 0.6% (+0.2 kg CO₂eq/kg beef), profit rose by 4%, work time increased by 18.9% (1.22 min), and net HEP efficiency improved to 0.6 (+4.5%). In GE, GWP decreased by 1.6% (−0.2 kg CO₂eq/kg beef), profit increased by 2.5%, work time increased by 9.5% (0.3 min), and net HEP efficiency slightly declined by 0.4%. For SR scenarios: In BE-SR, profit improved by EUR 48,000 (+28%), beef production doubled to 83,691 kg carcass/year, and GWP dropped to 13.2 kg CO₂eq/kg carcass (−52%). Net HEP efficiency exceeded 1.0 due to grass and by-product feeding. In FR-IT-SR, beef carcass production increased by 17% to 19,317 kg, profit rose by 20%, and GWP was maintained (−0.5%). Net HEP efficiency exceeded 1.0 only at stocking rates below 1.1 LU/ha. In GE-SR, profit increased by 1.5%, GWP decreased by 1%, beef production rose by 13% to 40,629 kg carcass, but net HEP efficiency declined to 0.4 (−20%) due to increased concentrate use.
**Clinical Implications:** The study demonstrates that FRG can improve farm profitability and marginally reduce emissions, but at the cost of increased labor. Crossbreeding dairy cows with beef breeds (Belgian Blue) offers substantial GHG reductions (up to 52%) by sharing environmental burdens with milk production. However, achieving net protein efficiency >1.0 requires stocking rates adapted to local grassland productivity (below 2.8 LU/ha in BE and below 1.1 LU/ha in FR-IT) and availability of by-products. The German case shows that without reducing stocking density, crossbreeding can worsen feed-food competition. The authors note that results require validation through field trials, as achieving sufficient fat scores in grass-finished crossbred bulls remains uncertain. The study highlights that system redesign requires changes throughout the value chain, not just on-farm modifications.