Comparative efficacy of oral and cloacal administration of Lactobacillus probiotics and postbiotics against Campylobacter jejuni colonization in broiler chickens

Campylobacter jejuni remains a major cause of foodborne illness worldwide, with poultry serving as the primary reservoir. In the absence of commercial vaccines or effective feed additives, probiotics and their byproducts (postbiotics) represent a promising and sustainable approach to reducing Campylobacter colonization in poultry. This study compared the efficacy of oral and cloacal administration of probiotic lactobacilli and their postbiotics in reducing Campylobacter colonization and modulating the cecal microbiome in broiler chickens. Day-old chicks were assigned to seven treatment groups that received either probiotics (live cells of four poultry-derived Lactobacillus strains: L. reuteri P43, L. acidophilus P42, L. animalis P38, and L. crispatus C25) or postbiotics (Lactobacillus supernatants) or their combination (whole cultures) orally or intracloacally, with a non-treated group serving as a control. Chickens were challenged with C. jejuni strain 81-176 at the second week of age, and cecal contents were collected at the fifth week for Campylobacter enumeration and microbiome profiling. The results revealed that both oral and cloacal administration of Lactobacillus cells significantly reduced Campylobacter cecal loads by 0.34 and 0.78 log₁₀, respectively, compared to the control. Significant differences in microbial richness and evenness were observed among treatment groups, with groups administered orally with probiotics, postbiotics, or their combination consistently showing higher alpha diversity indices than controls. NMDS ordination confirmed distinct community clustering among the treatment groups. Differential abundance analysis (MaAsLin2) further revealed that Ruminococcus was significantly enriched in the group receiving intracloacal postbiotic treatment, whereas the genus unclassified Firmicutes was more abundant in the group that received the combined probiotic-postbiotic treatment orally. Opportunistic genera, such as Escherichia-Shigella and Faecalicoccus, were significantly higher in the control group compared to all treated groups. Overall, while probiotics and postbiotics, whether given alone or together, modulated the gut microbial composition in Campylobacter-infected broilers, the administration of probiotic cells offered additional benefits by reducing Campylobacter colonization.