Relationships between diets different in fibre type and content with growth, Escherichia coli shedding, and faecal microbial diversity after weaning

Insoluble non-starch polysaccharides (iNSP) can decrease enterotoxigenic E. coli (ETEC) shedding in the gastrointestinal tract (GIT) and reduce post-weaning diarrhoea (PWD), whilst higher levels of soluble NSP (sNSP) have been associated with increased PWD (Pluske et al. 2002). A number of mechanisms such as reduced retention time, inhibition of mucosal E. coli adhesion and proliferation of butyrate-producing bacteria have been suggested to explain the beneficial effects of more iNSP in the diet (Lindberg 2014). However associations between dietary iNSP levels, specific microbial species and effects on production and ETEC shedding after weaning have not been explored in detail. The hypothesis tested was that pigs fed iNSP would have a higher abundance of butyrate-producing bacteria that in turn is correlated to indices of production and ETEC shedding.

An experiment having a 2 × 4 factorial arrangement of treatments using 48 individually-housed male weaner pigs (initial body weight 8.8 ± 0.05 kg; mean ± SEM) was conducted, with factors being low and high sNSP (7 versus 28 g soluble arabinoxylan/kg) and four levels of iNSP added as Opticell^® (equivalent to 5.5, 19.0, 34.5 and 51 g iNSP/kg). Faecal samples were collected pre- (day 5) and post- (day 9) infection with ETEC. Faecal β-haemolytic E. coli shedding (after Heo et al. 2009) and average daily gain (ADG) was measured. Extracted faecal DNA was quantified, amplified by polymerase chain reaction and sequenced. All sequencing data was analysed using the QIIME pipeline and the relationship between dietary fibre, microbial diversity and production indices was explored using linear regression analysis (R: Free Software Foundation’s GNU General Public License).

Increasing dietary iNSP improved growth performance and reduced E.coli shedding (Fig. 1a). It was also associated with an increased relative abundance of Christensenellaceae (a butyrate producer) and decreased abundance of Lactobacillaceae (a lactate producer) (Fig. 1b). In contrast, increasing dietary sNSP significantly decreased abundance of Christensenellaceae (data not shown). Christensenellaceae play a key role in maintaining GIT structure and function by forming syntrophic partnerships with Methanobrevibacter (the main methanogen in the GIT). Christensenellaceae alters host gene expression and reduces inflammation during E. coli infection, and has been associated with lean and healthy humans (Guilloteau et al. 2010). Increasing iNSP content in the diet altered the balance between butyrate and lactate producing taxa that in turn increased ADG and decreased ETEC count.

Fig. 1.  The influence of increasing insoluble fibre diet intake (supplied as Opticell^®) on (a) average daily gain (□) and faecal β-haemolytic E. coli score assessed form 1-5 (■), and (b) the relative abundance of Christensenellaceae (○) and Lactobacillaceae (●) in the first 2 weeks after weaning following infection with enterotoxigenic E. coli (mean ± SEM; n = 3).