Effects of Ligilactobacillus salivarius on the control of pullorum disease and cecal microbiota in red-feathered native chickens

Pullorum disease (PD), caused by Salmonella Pullorum (SP), remains a persistent challenge in native chicken production in Asia. Recurrent outbreaks and reliance on antibiotics have raised concerns about antimicrobial resistance. This study established a reproducible clinical PD model in red-feathered native chickens (RFCs) and evaluated Ligilactobacillus salivarius (LS) as a potential alternative to antibiotic. Oral administration of a field SP isolate (SPB6) at 1 × 10⁸ CFU per chick for four consecutive days induced typical PD signs and persistent bacterial colonization, whereas a single-dose challenge failed to produce consistent disease. Using this model, 100 SP-free RFCs were randomly assigned to five groups of 20 RFCs each: SP challenge only (A), SP + amoxicillin treatment (B), LS prophylaxis + SP (C), SP + nine-day LS treatment (D), and an unchallenged control group (E). Both amoxicillin and LS treatments reduced SP shedding and tissue colonization; notably, nine-day LS regimen achieved sustained suppression of SP isolation rates and bacterial loads comparable to those observed with amoxicillin on days 7, 10, and 17 after infection. Metagenomic analysis in cecal microbiota revealed that nine-day LS treatment enriched the abundance of short-chain fatty acid-producing species, such as Faecalicatena contorta and Lacrimispora saccharolytica, which are associated with intestinal integrity and immune resilience. In conclusion, LS reduced SP shedding and intestinal colonization, with greater efficacy following prolonged administration. LS also modulated the cecal microbiota in PD-affected RFCs by increasing the relative abundance of beneficial taxa. These findings provide experimental support for the evaluation of LS as a potential alternative to antibiotics for PD control. Further studies that extend the duration of LS administration are warranted and are likely to enhance its protective effects.