Gut microbiota and bile acid profiles in purebred vs. crossbred sows: links to oxidative stress and inflammation in late gestation

Understanding the interactions between gut microbiota, bile acid (BA) metabolism and systemic health is critical for supporting gestational physiological stability in sows, especially during the physiologically demanding late gestation period. Although physiological advantages vary by breed in late-gestation sows, the microbiota-related mechanisms underlying these differences remain poorly understood. This study compared serum antioxidant enzyme activity, oxidative damage markers, inflammatory cytokine levels, gut microbiota composition (analysed via 16S rRNA sequencing), and BA profiles (assessed through targeted metabolomics) between purebred large white (LW) and large white×landrace (LW×LR) crossbred sows during late gestation. Results showed that LW×LR crossbred sows exhibited significantly higher serum superoxide dismutase (SOD) activity and IL-10 levels, alongside reduced IL-6 levels (<i>P</i><0.05), indicating enhanced antioxidant and anti-inflammatory capacity. Gut microbiota analysis revealed greater alpha diversity (Shannon indices) and a lower Simpson index, along with distinct beta diversity (<i>P</i><0.05) in crossbred sows, with notable enrichment of functional taxa such as <i>Treponema</i> and <i>Prevotella</i>. Additionally, faecal concentrations of modified BAs, specifically 3-oxolithocholic acid and 7-ketolithocholic acid, were significantly elevated, correlating with increased abundance of gut microbiota encoding BA: Na⁺ symporter (BASS family) proteins, as well as the increased 7-<i>α</i>-hydroxysteroid dehydrogenase activity (<i>P</i><0.05). In contrast, LW sows exhibited enrichment of <i>Terrisporobacter</i> and <i>Clostridium sensu</i> stricto 1, alongside accumulation of primary (e.g. chenodeoxycholic acid) and unconjugated BAs (e.g. deoxycholic acid) (<i>P</i><0.05). Correlation analysis demonstrated that the accumulation of <i>Terrisporobacter</i> and primary BAs was positively correlated with exacerbation of inflammation. In conclusion, under intensive production conditions, significant differences in the gut microbiota-BA axis between LW and LW×LR crossbred sows may underlie variations in oxidative stress and inflammatory status during late pregnancy. These findings provide valuable insights into microbiome-BA-host associations underlying the physiological advantages (enhanced antioxidant and anti-inflammatory capacity) of crossbred sows.