Biosecurity has gained significant interest in farm animal health in recent years. However, in dairy cattle farms, there is slight, or no implementation of biosecurity practices recommended by official authorities and techno-scientific experts. This situation might be explained by the tension between old farming traditions and routines and veterinary recommendations. We draw upon Lefebvre's threefold model of space, which addresses spatial practices (old traditions and routines), representations of space (recommendations) and representational space (final implementation of biosecurity measures), constituting security ecologies to understand what might be happening by using an ethnographic approach on two farms in Galicia and two in Catalonia in Spain. The three biosecurity practices considered are management of dead animals, control of vectors and pests, and animal management. The results show that farms have different specific contexts, and that the reasons behind the positions of farmers and veterinarians, effective communication and common sense need to be considered. Security ecologies based on Lefebvre's model could therefore be a positive mechanism for ensuring the implementation of biosecurity, beyond the visions of authorities or specialists.