Number of farms in which all animals sampled for a given age group were positive (dark grey) or at least one sample was seronegative (light grey). The percentage of farms in which all samples from the indicated age group were positive is shown above each bar. Only those farms from which nine or more animals per age group were tested have been included in the graph.
Alonso-Padilla et al. BMC Research Notes 2012 5:675 doi:10.1186/1756-0500-5-675