Fig. 2

Biosecurity characterization of 18 intensive Spanish pig farms. a Boxplots of the total, external and internal biosecurity scores per farm. b Principal component analysis followed by an UPGMA hierarchical clustering analysis for grouping farms according to their scores in external and internal biosecurity practices. C) Boxplots of total, internal and external biosecurity scores within each farm cluster. D) Boxplot of the number of fattening pigs per feedlot within each farm cluster. Each farm is represented by a dot with horizontal jitter for visibility. The horizontal box lines represent the first quartile, the median, and the third quartile. Whiskers include the range of points within the 1.5 interquartile range. The differences per cluster were evaluated with the Wilcoxon signed-rank test