Physicochemical characteristics of fibre sources and their effects on in vitro <i>Escherichia coli</i> infection in IPEC-J2 cells

Feed-related strategies, such as adding fibre to weaned-piglets’ feed, have been suggested to reduce the impact of Escherichia coli (E. coli) in swine production. We performed physicochemical analysis of fibre sources (wheat bran, commercial insoluble fibre (commercial IF), almond shell, beet pulp, dry olive cake, and oat hull) and examined the effects of their soluble fractions on fimbriated (F4) and non-fimbriated (NF) E. coli. Intestinal porcine epithelial (IPEC-J2) cells were used as an in vitro model. Almond shell and commercial IF contained more insoluble and total dietary fibre (p < 0.001), while wheat bran contained the least total dietary fibre (p < 0.001). Beet pulp contained the most soluble fibre and had the highest water holding capacity (p < 0.001). Commercial IF had the highest swelling capacity (p < 0.001) and dry olive cake the highest cold solubility (p < 0.001). Based on adherence assays, wheat bran, oat hull, almond shell, and dry olive cake significantly prevented E. coli F4 from adhering to IPEC-J2 cells, whereas for NF E. coli, only dry olive cake reduced bacterial infection (p < 0.05). Dry olive cake was the most effective in reducing expression of proinflammatory cytokines, predominantly interleukin 8 (IL-8) and tumour necrosis factor-α (TNF-α) (p < 0.001). In conclusion, aqueous extracts of wheat bran, oat hull, almond shell, and dry olive cake contain compounds that interfere with E. coli F4 adherence to IPEC-J2 cells.