Effect of successive fibre diets on nutrient digestibility and faecal microbiota composition in pigs

Gut microbial population acts in complement with its host through nutrient digestion and health of the gastrointestinal tract. Changes in microbiota composition may then lead to changes in nutrient digestibility. The present study aimed at determining the effects of dietary fibre content on gut microbiota composition and apparent faecal nutrient digestibility in pigs. Furthermore, the relationships between microbiota and digestibility coefficients were investigated. Growing-finishing pigs (from 35 to 74 kg mean body weight) were fed alternatively a low-fibre (LF) and a high-fibre (HF) diet during 4 successive 3-week periods. Data collection for digestibility measurements was achieved during the last week of each period and faecal microbiota was collected at the end of each period for 16S rRNA gene sequencing. The two diets fed by the pigs could be discriminated using 31 predicting OTUs in a sparse partial least square discriminant analysis (mean classification error-rate 3.9%). Furthermore, microbiota was resilient to diet effect. Pearson correlations between microbiota composition and apparent digestibility coefficients of energy, protein, cellulose and hemicellulose emphasized the fact that in LF group, Clostridiaceae and Turicibacter were negatively correlated with protein and energy digestibility coefficients whereas Lactobacillus was positively correlated. In addition, Lachnospiraceae and Prevotella were negatively correlated with cell wall components digestibility. In HF diet, no significant correlation between microbiota and digestibility was found. The present study demonstrates that 3 weeks of adaptation to a new diet seem to be sufficient to observe resilience in growing pigs gut microbiota. In addition, faecal microbiota can be used to classify pigs according to their diet. Because some bacterial family and genera are favourable to digestibility, this study suggests that manipulations of bacterial populations can improve digestibility and feed efficiency. This study is part of the Feed-a-Gene Project, funded from the European Union’s H2020 Programme under grant agreement no. 633531.