Investigation of Metabolites in Feces and Plasma Associated with the Number of Piglets Weaned per Sow per Year

<b>Background</b>: 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. <b>Methods</b>: 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. <b>Results</b>: 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 (<i>p</i> < 0.05) in group H. The concentrations of plasma metabolites <i>p</i>-cresyl sulfate, <i>p</i>-cresyl glucuronide and trimethylamine <i>N</i>-oxide (TMAO) were higher (<i>p</i> < 0.05) in group L than in group H, while the opposite was true for the acetate concentration (<i>p</i> < 0.05). Among plasma biochemicals, tumor necrosis factor (TNF)-alpha and potassium concentrations were higher (<i>p</i> < 0.05) in group L. <b>Conclusions</b>: Blood metabolites, especially gut microbiota-derived metabolites, seemed to be associated with the performance related to sow reproduction. Particularly, harmful metabolites such as <i>p</i>-cresyl glucuronide, <i>p</i>-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 <i>p</i>-cresyl glucuronide, <i>p</i>-cresyl sulfate, TMAO and TNF-alpha could be useful physiological indicators to understand sow reproductive performance.