Response of gastrointestinal fermentative activity and colonic microbiota to protected sodium butyrate and protected sodium heptanoate in weaned piglets challenged with ETEC F4⁺

ABSTRACT

This study aimed to evaluate the potential of two new fat-protected butyrate or heptanoate salts to improve gut health and control post-weaning colibacillosis in weaning piglets challenged with enterotoxigenic Escherichia coli (ETEC) F4⁺, particularly focusing on their impact on intestinal microbiota and fermentative activity along the gastrointestinal tract (GIT). Seventy-two 21-d-old pigs were fed a plain diet (CTR) or supplemented with sodium butyrate (BUT) or sodium heptanoate (HPT), both at 0.3%. After a week of adaptation, animals were orally challenged at days 8 and 9 with 5.8 · 10⁹ and 6.6 · 10¹⁰ cfu, respectively, and were euthanised on d 4 and d 8 post-inoculation (PI) (n = 8) to collect blood, digesta and tissue samples and characterise microbial groups, pathogen loads (qPCR), fermentation, ileal histomorphometry and immune markers. Colonic microbiota was analysed by 16S rRNA gene MiSeq sequencing. Supplementing both acid salts did not compensate clinical challenge effects nor performance impairments and neither histomorphometry nor serum biomarkers. Changes in the gastric fermentative activity were registered, BUT reducing lactic acid concentrations (day 8 PI), and with HPT fewer animals presenting detectable concentrations of propionic, butyric and valeric acids. At ileum BUT increased acetic acid concentration (day 8 PI), and both additives reduced short-chain fatty acids (SCFA) in the colon. Increases in enterobacteria and coliforms counts in ileal digesta (day 4 PI, p < 0.10) and mucosa scrapes (p < 0.05) were registered although E. coli F4 gene copies were unaffected. Regarding changes in the colonic microbiota (day 4 PI), Prevotellaceae and Prevotella were promoted with BUT supplementation whereas only minor groups were modified in HPT-treated animals. Summarising, although the pathogen loads or inflammatory mediators remained unresponsive, butyrate and heptanoate showed a significant impact on microbial fermentation along the whole GIT, being able to modify different bacterial groups at the colon. It could be hypothesised that these effects might be mediated by a carry-over effect of the changes observed in gastric fermentation, but possibly also to a better nutrient digestion in the foregut as a result of the reduced colonic SCFA concentrations.

KEYWORDS:

• 16S rRNA gene
• enterotoxigenic Escherichia coli
• feed additives
• fermentation products
• intestinal microorganisms
• organic acid salts
• sodium butyrate
• weaner pigs

Acknowledgments

We wish to thank Irene Martínez Barniol for her support of the experimental trial and Jan-Pieter Löbbing, professional translator, for his correction of the article’s language and style.

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 PRJEB30494.

Supplementary material

Supplemental data for this article can be accessed at https://doi.org/10.1080/1745039X.2019.1641376.

Additional information

Funding

This work was supported by the “PORCDIGEST” project (IDI-20140262) funded by the CDTI and the Ministerio de Economía y Competitividad of Spain; and the pre-doctoral FI grant of the Generalitat de Catalunya (Spain) awarded to Paola López-Colom; Agència de Gestió d’Ajuts Universitaris i de Recerca [2017FI_B1_00055].