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Short and medium-chain fatty acids (SCFA and MCFA, respectively) are commonly used as feed additives in piglets to promote health and prevent post-weaning diarrhoea. The mechanism and site of action of these fatty acids can differ, so a combined supplementation could result in a synergistic action. Considering this, the objective of this trial was to assess the potential of two new in-feed additives based on butyrate or heptanoate, protected with sodium salts of MCFA from coconut distillates, against enterotoxigenic Escherichia coli (ETEC) F4+ using an experimental disease model. For that purpose, two independent trials were performed in 48 early-weaned piglets fed a control diet (CTR) or a diet supplemented with MCFA-protected sodium butyrate (BUT+; Trial 1) or sodium heptanoate (HPT+; Trial 2). After 1 week of adaptation, piglets were challenged with a single oral inoculum of ETEC F4+. One animal per pen was euthanised on days 4 and 8 post-inoculation (PI) and the following variables assessed: growth performance, clinical signs, gut fermentation, intestinal morphology, inflammatory mediators, pathogen excretion and colon microbiota.
Results showed that none of the additives recovered growth performance or reduced diarrhoea when compared to the respective negative controls. However, both elicited different responses against ETEC F4+. First, the BUT+ additive did not lead to reduce E. coli F4 colonisation but enterobacterial counts and goblet cell numbers in the ileum were increased on day 8 PI and this followed higher serum TNF-α concentrations on day 4 PI. The Firmicutes:Bacteroidetes ratio was nevertheless increased. Second, findings in the HPT+ treatment trial included fewer animals featuring E. coli F4 in the colon and reduced Enterobacteriaceae (determined by 16S RNA sequencing) on day 4 PI. In addition, while goblet cell numbers were lower on day 8 PI, total SCFA levels were reduced in the colon.
In conclusion, MCFA-protected heptanoate was effective against ETEC F4+, while MCFA-protected butyrate evidenced its potential trophic effect on the intestinal epithelium likely reinforcing the gut barrier.
López-Colom P, Castillejos L, Rodríguez-Sorrento A, Puyalto M, Mallo JJ, Martín-Orúe SM. Impact of in-feed sodium butyrate or sodium heptanoate protected with medium-chain fatty acids on gut health in weaned piglets challenged with Escherichia coli F4+. Archives of Animal Nutrition. 2020; 74(4): 271-295. https://doi.org/10.1080/1745039X.2020.1726719