Dietary fiber supplementation during late gestation affects steroidogenesis, antioxidant capacity, gut microbiota and placental metabolomics of Rongchang sows

Oxidative stress can impair placental function and sow health. This experiment aimed to explore the impacts of inulin and cellulose as sources of dietary fiber (DF) on reproductive performance, steroidogenesis, antioxidant capacity, placental metabolomics, and fecal microbiota of Rongchang sows from d 85 of gestation to parturition. Sixty sows (parity: 5.07 ± 0.24, backfat thickness: 43.06 ± 0.78 mm) were randomly assigned to 4 groups ( n = 15): the control group fed a basal diet (CON), and the other 3 groups receiving diets supplemented with 21.8%, 43.6% or 65.5% more DF than the CON group, named as DF1, DF2, and DF3, respectively. The DF supplementation had no significant effect on total litter size, number of piglets born alive, and piglet birth weight ( P > 0.05). Compared with the CON group, the concentrations of serum estradiol (E2) and progesterone (P4) on d 108 of gestation increased in linear and quadratic manners and reached their maximums in the DF1 group, while those in the placenta increased quadratically and also maximized in the DF1 group ( P < 0.001). Maternal DF supplementation quadratically increased the serum glutathione peroxidase (GSH-Px) activity on d 108 of gestation ( P = 0.036), with the highest activity observed in the DF1 group, while the superoxide dismutase (SOD) activity tended to increase quadratically ( P = 0.066) and peaked in the DF2 group. In addition, compared with the CON group, DF supplementation quadratically increased the fecal concentrations of acetate, butyrate, and total short-chain fatty acids (SCFAs) on d 108 of gestation ( P < 0.05), all of which maximized in the DF1 group. The relative abundances of SCFAs-producing genera Parabacteroides , norank_f_F082 , and norank_f_UCG-010 were significantly higher in the DF-supplemented groups than in the CON group ( P < 0.05). Correlation analysis indicated that the abundance of Parabacteroides was negatively correlated with serum IL-6 concentrations ( P = 0.027), while serum E2 and P4 concentrations were positively correlated with fecal concentrations of propionate, butyrate, and total SCFAs ( P < 0.01). Untargeted metabolic analysis further revealed that the DF1 group significantly affected placental metabolites associated with linoleic acid metabolism, the PPAR signaling pathway, and cholesterol metabolism. These findings suggest that moderate DF supplementation optimally enhances the health status of late-gestating sows by modulating gut microbiota-derived SCFAs and placental metabolism.