Piglet weight gain during the first two weeks of lactation influences the immune system development

Abstract The aim of this study was to investigate the effect of the piglet growth during the first week of life on ileal expression of genes and on development of the immune system. Eight litters adjusted to 12 piglets were used. Within each litter, the piglet that showed the lowest weight gain (LWG; n = 8) and the one that showed the highest weight gain (HWG; n = 8) in their first week of life were enrolled. Peripheral blood mononuclear cells (PBMC) were isolated on days 8 and 16 to characterize cellular population profiles and to assess ex-vivo secretion of interleukin-10 (IL-10), IL-6 and tumor necrosis factor-α (TNF-α). On day 16, piglets were euthanized and ileum samples were collected to extract RNA for microarray analysis and gene expression by qPCR. As expected, growth performance of LWG piglet was impaired compared to HWG piglets (P  + B cells significantly increased in blood of heavier HWG piglets while the percentage remained constant in smaller LWG piglets ( P weight x day = 0.01). For the CD4 + CD8α − Th cells, a marked increase was observed in LWG piglets from 8 to 16 days of age ( P  =  0.002) whereas no significant change occurred in HWG piglets. Percentages of CD14 + monocytes and other MHC-II + cells were respectively higher and lower on day 8 compared to day 16 for both groups of piglets ( P P IL-10, SOD1, NOS2, NOD2, TLR4, TLR9, CD40 and CD74 expressions were significantly decreased (P  MYD88 and NFkBiA showed a tendency to decrease (0.05 ≤ P