Due to increasing public health concerns that food animals could be reservoirs for antibiotic resistant organisms, calls for reduced current antibiotic use on farms are growing. Nevertheless, it is challenging for farmers to perform this reduction without negatively affecting technical and economic performance. As an alternative, improved management practices based on biosecurity and vaccinations have been proven useful to reduce antimicrobial use without lowering productivity, but issues with insufficient experimental design possibilities have hindered economic analysis. In the present study a quasi-experimental approach was used for assessing the economic impact of reduction of antimicrobial use coupled with improved management strategies, particularly biosecurity strategies. The research was performed on farrow-to-finish pig farms in Flanders (northern region of Belgium). First, to account for technological progress and to avoid selection bias, propensity score analysis was used to compare data on technical parameters. The treatment group (n = 48) participated in an intervention study whose aim was to improve management practices to reduce the need for use of antimicrobials. Before and after the change in management, data were collected on the technical parameters, biosecurity status, antimicrobial use, and vaccinations. Treated farms were matched without replacement with control farms (n = 69), obtained from the Farm Accountancy Data Network, to estimate the difference in differences (DID) of the technical parameters. Second, the technical parameters’ DID, together with the estimated costs of the management intervention and the price volatility of the feed, meat of the finisher pigs, and piglets served as a basis for modelling the profit of 11 virtual farrow-to-finish pig farms representative of the Flemish sector. Costs incurred by new biosecurity measures (median +€ 3.96/sow/year), and new vaccinations (median € 0.00/sow/year) did not exceed the cost reduction achieved by lowering the use of antimicrobials (median −€ 7.68/sow/year). No negative effect on technical parameters was observed and mortality
of the finishers was significantly reduced by−1.1%. Even after a substantial reduction of the antimicrobial treatments, the difference of the enterprise profit increased by + €2.67/finisher pig/year after implementing the interventions. This result proved to be robust after stochastic modelling of input and output price volatility. The results of this study can be used by veterinarians and other stakeholders to incentivise managers of farrow-to-finish operations to use biosecurity practices as a cost-effective way to reduce antimicrobial use.