The aim of this study was to investigate the microbiota composition and its potential interactions across seven gut locations (stomachs, jejuna, ilea, ceca, proximal colons, distal colons, and recta) in weaned pigs to identify key influencing microbiotas. To compare between microbiota compositions, 16S rRNA gene amplicon sequencing was performed. Six 70-day-old healthy crossbred (Duroc × Large White × Landrace) piglets were introduced as donors. A Bayesian network (BN) was used to examine the directional interactions among the microbiotas evaluated (seven mucosal and seven digesta microbiotas). Based on edge connectivity frequency, the microbiota in jejunal mucosa was the central hub node, influencing other microbiotas, especially the mucosal microbiotas of the ileum, cecum, distal colon, and rectum. The jejunal mucosa was dominated by Prevotella and lactobacilli, both recognized for their contributions to pig health. Among Prevotella, Prevotella copri and Prevotella sp. were predominant in jejunal mucosa (4.6% and 2.9%, respectively). Lactobacilli, including eight distinct species, were distributed throughout the gastrointestinal tract. Notably, Ligilactobacillus salivarius and Lactobacillus amylovorus, known as immune-enhancing bacteria, were abundant in jejunal mucosa (1.0% and 0.8%) and digestas (0.9% and 19.2%), respectively. The BN identified rectal mucosa and digestas as two terminal nodes, influenced by upstream microbiotas in the gastrointestinal tract. This finding supports the link between fecal microbiota and pig productivity, as the fecal microbiota, closely resembling the rectal microbiota, reflects the conditions of the microbiota throughout the gastrointestinal tract.

Background: Sow reproductive performance is a critical parameter for the productivity of commercial pig farms. Gut microbiota is associated with performance in sow reproduction. At least, under healthy conditions, microbial metabolites from the gut microbiota are considered major contributors to host physiological regulation and productivity. However, information on the differences in gut-derived metabolites related to the sow reproductive performance remain scarce. Our aim was to investigate the relationship between the reproductive performance and microbial metabolite levels in sow’s feces and plasma. Methods: We selected four commercial farms: two with high- (group H) and two with low-reproductive performance (group L). Sows had their feces and blood collected. Results: Except for the iso-butyrate concentration, fecal short-chain fatty acid concentrations remained unchanged between groups. Among intestinal putrefactive metabolites, the indole concentration was higher (p < 0.05) in group H. The concentrations of plasma metabolites p-cresyl sulfate, p-cresyl glucuronide and trimethylamine N-oxide (TMAO) were higher (p < 0.05) in group L than in group H, while the opposite was true for the acetate concentration (p < 0.05). Among plasma biochemicals, tumor necrosis factor (TNF)-alpha and potassium concentrations were higher (p < 0.05) in group L. Conclusions: Blood metabolites, especially gut microbiota-derived metabolites, seemed to be associated with the performance related to sow reproduction. Particularly, harmful metabolites such as p-cresyl glucuronide, p-cresyl sulfate and TMAO were of importance, because they are potentially inflammation factors. In fact, TNF-alpha was stimulated in group L. According to our results, we estimated that p-cresyl glucuronide, p-cresyl sulfate, TMAO and TNF-alpha could be useful physiological indicators to understand sow reproductive performance.