Fig. 3

Dynamics of Ct values of PRRSV-positive samples from challenged pigs. The Ct values with letters a, b and c are with significant differences between different types of positive samples. Different letters indicate significant statistical differences (P < 0.05), and the same letter indicates no significant statistical differences (P > 0.05). The letter ‘N’ indicates there were not enough PRRSV positive samples for one-way ANOVA of Ct values