Dietary supplementation with fermented milk strengthened the expression of claudin-3 and occludin in the jejunum (p < 0.05) and tended to enhance the expression of claudin-1 (p = 0.06) and ZO-2 (p = 0.08), but it did not cause a significant change in jejunal ZO-1 expression in IUGR piglets (p = 0.12). Here, CLDN1 is linked to fetal growth restriction.