Marginal plots of mean age at 100 kg and adverse effects of influenza A(H1N1)pdm09 virus infection. The plots show the predicted mean ages of pigs at 100 kg for the five groups of pigs based on the model presented in Table 6. The gradient of the line joining the mean for each group and the confidence intervals indicate whether there is any difference between the groups due to their infection status. Comparisons were made between the four infected groups and the reference seronegative group. Abbreviations: INFGP = Infection status group; SEROPOS = seropositive pigs, SERONEG = seronegative pigs, VIR1 = PCR-positive pigs at bodyweight between 33 kg and 60 kg (GF1); VIR2 = PCR-positive pigs at bodyweight between 61 kg and 80 kg (GF2); VIR3 = PCR-positive pigs at bodyweight between 81 kg and 100 kg (GF3).