Plasma total IgG concentrations (g/L) during the time course of the experiment in control (C) and co-infected (MH1N1) pigs.

Standard errors of the mean (SEM) of control (C) and co-infected (MH1N1) conditions are presented with ad libitum (AL) and feed restricted (FR) pigs pooled together (C-AL+C-FR vs. MH1N1-AL+MH1N1-FR) because the effect of the feeding level (-AL or -FR) and its interactions with the effects of infection (I) and time (T) were not significant. a,b: concentrations with different letters are significantly different with P<0.001.