Effect of fructo-oligosaccharides and different doses of Bifidobacterium animalis in weaning diet on bacterial translocation and TLRs gene expression in pigs

Objective: Our aim was to study the possible synergic action of one prebiotic with increasing dietary doses of a probiotic strain of Bifidobacterium animalis on the translocation of bifidobacteria and on TLRs gene-expression in different organs of weaned piglets. Methods: Sixty four pigs, reared from 21 to 35 days of age, fed eight different diets according to a 2 X 4 factorial design: control diet (C), or C supplemented with three different levels of B. animalis (107, 109, 1011 cfu per day), crossed with 0% or 2% sugar beet fructo-oligosaccharides (bFOS). Pigs were then sacrificed, and jejunum mucosa, ileo-cecal lymph nodes and liver were sampled to determine the presence of bifidobacteria spp. DNA and to quantify the expression of TLR2, TLR4 and TNFα-encoding genes. Results: We found bifidobacteria spp. genus-specific DNA in lymph nodes of subjects from all dietary treatments, including the control diet, but increasing with the bifidobacteria oral dose (P = 0.065). Linear effect of the dose of the B. animalis on the expression of TLR2-encoding gene in the lymph nodes was observed when bFOS was added in the diet (P < 0.05). The TNFα-encoding gene expression was positively correlated with TLR4 and TLR2-encoding genes expression (P < 0.001 and P < 0.01 respectively) and negatively correlated with bifidobacteria DNA (P < 0.05). Moreover, the expression of TLR4-encoding gene showed a positive correlation with the TLR2-encoding gene expression (P < 0.001). On the contrary, there was no correlation between the expression of TLR2 and TLR4-encoding genes with the bifidobacteria DNA. Conclusion: Early after weaning the translocation of the commensal bacteria in the ileo-cecal lymph nodes is a physiological process. Moreover the diet affected the expression of TLR2-encoding gene.