Effect of purified β-glucans derived from Laminaria digitata, Laminaria hyperborea and Saccharomyces cerevisiae on piglet performance, selected bacterial populations, volatile fatty acids and pro-inflammatory cytokines in the gastrointestinal tract of pigs.

b-Glucans have been identified as natural biomolecules with immunomodulatory activity. The first objective of the present study was to compare the effects of purified b-glucans derived from Laminaria digitata, L. hyperborea and Saccharomyces cerevisiae on piglet performance, selected bacterial populations and intestinal volatile fatty acid (VFA) production. The second aim was to compare the gene expression profiles of the markers of pro- and anti-inflammation in both unchallenged and lipopolysaccharide (LPS)-challenged ileal and colonic tissues. b-Glucans were included at 250 mg/kg in the diets. The b-glucans derived from L. hyperborea, L. digitata and S. cerevisiae all reduced the Enterobacteriaceae population (P,0·05) without influencing the lactobacilli and bifidobacteria populations (P.0·05) in the ileum and colon. There was a significant interaction between gastrointestinal region and b-glucan source in the expression of cytokine markers, IL-1a (P,0·001), IL-10 (P,0·05), TNF-a (P,0·05) and IL-17A (P,0·001). b-Glucans did not stimulate any pro- or anti-inflammatory cytokine markers in the ileal epithelial cells. In contrast, the expression of a panel of pro- and anti-inflammatory cytokines (IL-1a, IL-10, TNF-a and IL-17A) was down-regulated in the colon following exposure to b-glucans from all the three sources. However, the data suggest that the soluble b-glucans derived from L. digitata may be acting via a different mechanism from the insoluble b-glucans derived from L. hyperborea and S. cerevisiae, as the VFA profile was different in the L. digitata-treated animals. There was an increase in IL-8 gene expression (P,0·05) in the gastrointestinal tract from the animals exposed to L. digitata following an LPS ex vivo challenge that was not evident in the other two treatment groups. In conclusion, b-glucans from both seaweed and yeast sources reduce Enterobacteriaceae counts and pro-inflammatory markers in the colon, though the mechanisms of action may be different between the soluble and insoluble fibre sources.