Genetic parameters of immune traits for Landrace and Large White pig breeds

Improving the immunocompetence towards pathogens represents a desirable objective of breeding strategies to increase resilience. However, the immune system is complex and the genetic foundation of the underlying components is not yet clarified. In the present study, we focused on 22 blood parameters of 1,144 Landrace (LR) and Large White (LW) piglets at the age of 6-7 weeks. The immune profiles covered immune cells, red blood cell characteristics and cytokines. Genetic parameters based on pedigree information along with possible environmental effects were estimated. Litter effects play an important role in the expression of immune parameters of their young progenies. Hence, litter impacts on the piglet's immune profile including the immune parameters of the dam itself were investigated by different models. To incorporate the complexity of the immune network, the data were further investigated with a principal component analysis. Immune traits showed low to high breed-specific heritabilities (h² ). Strong positive r_g were estimated among red blood cell characteristics (0.77-0.99) and among cytokines (0.48-0.99). Neutrophils and lymphocytes illustrated a high negative r_g (-0.96 to -0.98). The litter impact on piglet's immunity was examined and strengthened already observed breed differences. In LR, h² (0.22-0.15) and litter effect (c² ) (0.52-0.44) for IFN-γ decreased after statistical consideration of maternal impact. In LW, a decrease in h² (0.32-0.18) for IFN-γ and an increase in c² (0.54-0.56) were observed. Here, sufficient correlations were detected within various immune traits and functional biological networks of principal components. Most immune traits are heritable and are promising to cover global breed-specific immunocompetence in pigs. The analysis of immune traits has to be extended in order to find an optimal range and to characterize relationships between immunity and performance to gain an improved immune system without accidental losses in productivity.