BackgroundLactulose as an effective prebiotic protects intestinal mucosal injury.Bacillus coagulansis widely used in feed additives because of its ability to promote intestinal health. Our previous study suggests that the combination of lactulose andBacillus coagulansmay be a good candidate as alternative for antibiotic growth promoters. However, the in vivo effects of lactulose andBacilluscoagulanson growth and intestinal health under immune challenge in piglets remains unclear. The objective of this study is to explore the protective effects of synbiotic containing lactulose andBacillus coagulanson the intestinal mucosal injury and barrier dysfunction under immune challenge in weaned piglets.MethodsTwenty four weaned piglets were assigned to 4 groups. Piglets in the CON-salineand LPS-LPSgroup were fed the basal diet, while others were fed either with chlortetracycline (CTC) or synbiotic mixture of lactulose andBacillus coagulansfor 32 d before injection of saline or lipopolysaccharide (LPS). Piglets were sacrificed 4 h after LPS injection to collect samples to determine intestinal morphology, integrity and barrier functions as well as relative genes and proteins.ResultsOur data showed that no differences were observed in the growth performance of the four test groups. LPS injection induced higher serum diamine oxidase activities,D-lactic acid levels, and endotoxin status, lower villus height and ratio of villus height to crypt depth, greater mRNA and lower protein expression related tight junction in both jejunum and ileum. In addition, a higher apoptosis index, and protein expression of Bax and caspase-3 were also observed in the LPS challenge group. Interestingly, dietary synbiotic mixture with lactulose andBacillus coagulansprotected against LPS-induced intestinal damage, barrier dysfunction and higher apoptosis as well as CTC.ConclusionsOur data suggest that dietary supplementation of synbiotic mixture with lactulose andBacillus coagulansshowed resilience to LPS-induced intestinal morphological damage, barrier dysfunction and aggressive apoptosis in piglets as well as the protective effects of CTC. These results indicate that synbiotic mixture of lactulose andBacillus coagulansshowed beneficial effects on performance and resilience to acute immune stress in weaned piglets.Supplementary InformationThe online version contains supplementary material available at 10.1186/s40104-023-00882-9.