Host-derived Limosilactobacillus reuteri supplementation improves piglet growth and gut integrity in heat-stressed sows.

Heat stress during late gestation and lactation impairs sow physiology and productivity, partly through altered stress responses, inflammation, and intestinal integrity. This study evaluated whether novel Limosilactobacillus reuteri strains isolated from high-performing sows under heat stress could mitigate these effects. Forty multiparous sows (twenty sows in parity three and twenty in parity four; average initial BW: 243.1 ± 18.2 kg) were assigned to a thermoneutral control (TN) or three heat-stress treatments: unsupplemented heat stress (HS), heat stress with a 4.65 log CFU/g L. reuteri (HS5), or heat stress with a 4.95 log CFU/g L. reuteri (HS10). Sow performance, stress indicators, inflammatory cytokines, antioxidant status, gut integrity markers, and fecal microbiota were assessed. Feed intake during lactation was higher in the TN and HS10 compared with the HS. Litter performance parameters showed no significant differences among groups. Piglet weight at weaning was increased (p = 0.015) in the TN and HS10 compared with the HS and HS5. Respiratory rate increased in heat-stressed sows. Hair cortisol concentrations were lower in the TN compared with the heat-stressed treatments. Serum tumor necrosis factor-alpha, interleukin (IL)-10, and IL-1β concentrations were lower in TN compared with heat-stressed groups. Serum zonulin was higher in HS than in TN and HS10, while occludin concentration was lower in TN compared with all heat-stress treatments. At the phylum level, the relative abundance of Firmicutes, Bacteroidota, and Spirochaetota was similar among groups. At the family level, the Pirellulaceae family was tended to be higher in HS than HS5 and HS10. At the genus level, the relative abundance of Terrisporobacter was higher in the HS10 compared with HS and HS5. Abundance of CPla-4_termite_group tended to increase in the HS. Supplementation with 4.95 log CFU/g host-derived L. reuteri strains improved feed intake and piglet growth under heat stress and modulated inflammatory and gut barrier markers, despite minimal effects on overall microbiota structure.