Short-chain fatty acids and L-lactate as feed additives to control Campylobacter jejuni infections in broilers.

The usefulness of butyrate, acetate, propionate and l-lactate for the control of Campylobacter jejuni infections in broilers was assessed. For this purpose, the effect of these acids on the growth of C. jejuni in broth and intestinal mucous was determined, as well as their influence on the invasiveness of C. jejuni in intestinal epithelial cells. From these in vitro obtained results, one acid was retained for use as a feed additive in an in vivo trial. Butyrate was the most successful of the short-chain fatty acids, with 12.5 mM being bactericidal for C. jejuni at pH 6.0. Propionate and acetate had a bacteriostatic effect at 50 mM. None of the short-chain fatty acids had a bactericidal effect at pH 7.5 at a maximum concentration of 50 mM. Mucous increased the minimum bactericidal concentration of butyrate, but not the bacteriostatic concentrations of propionate or acetate. When C. jejuni was incubated in growth subinhibitory concentrations of butyrate, acetate or propionate or 25 mM L-lactate, no alteration in the invasive capabilities of C. jejuni in Caco-2 cells was observed. The addition of butyrate-coated micro-beads to the feed was unsuccessful to reduce C. jejuni caecal colonization in a seeder model using 2-week-old broilers. In conclusion, despite the marked bactericidal effect of butyrate towards C. jejuni in vitro, butyrate-coated micro-beads do not protect broilers from caecal colonization with C. jejuni in the applied test conditions. This might be partially ascribed to the protective effect of mucous and the rapid absorption of butyrate by the enterocytes.