Fig. 1

a The four buildings for fatteners were in a slope to the fields, 15 m apart from each other with the aim to reduce transfer of microbes between the buildings. To improve the biosecurity, an entrance for staff with possibilities to change shoes and wash hands that also stored hay silage was built on the gable to the left of each building and a space for delivering market weight pigs to slaughter was built on the gable to the right of each building. b Pigs had access to an outdoor area that also was used for dunging. c Each unit with two pens that housed 20 pigs each had ventilation and manure systems that were separated from the other units. Each pen had two automatic feeders where four pigs could eat simultaneously and the door under the windows lead to the outdoor facility. d The mechanical ventilation was regulated through the windows by a bimetallic window opener. Courtesy of PerArne Mattsson