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⁺

ABSTRACT

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. Considering that the mechanism and site of action of these fatty acids can differ, a combined supplementation could result in a synergistic action. Considering this, it was aimed 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. 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⁺ (minimum 1.4 · 10⁹ cfu). 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. 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⁺. 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. 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. Results indicate the efficacy of MCFA-protected heptanoate against ETEC F4⁺ and emphasise the potential trophic effect of MCFA-protected butyrate on the intestinal epithelium likely reinforcing the gut barrier.

KEYWORDS:

• 16S amplicon
• medium-chain fatty acids
• weaned piglet
• post-weaning diarrhoea
• short-chain fatty acids

Acknowledgments

We wish to thank Jaume Gou for help with the experimental trial, and Ana Burton for editorial assistance.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The data that support the findings of this study are available from the corresponding author, LC, upon reasonable request. In the case of the raw sequences, these are openly available in the European Nucleotide Archive (ENA) at https://www.ebi.ac.uk/ena, accession number PRJEB30499.

Additional information

Funding

This work was funded by the project “PORCDIGEST” [IDI-20140262] of the CDTI and Ministerio de Economía y Competitividad and a pre-doctoral FI grant from AGAUR (Spain) awarded to Paola López-Colom; Agència de Gestió d’Ajuts Universitaris i de Recerca [FI 2016].