Figure 5

Levels of serum antibodies. Anti-N antibodies were detected using the HerdCheck® PRRS ELISA kit with the cutoff value of S/P ratio of 0.4 (A) and anti-GP2/GP5 antibodies were detected using the LIVTESTSUISPRRS A/S® kit with the relative index (expressed as a percentage) greater than 20 as positive (B). Each point represents the mean (±S.D.) generated from six groups of piglets on different DPIs or DPCs.