The efficacy of probiotics and prebiotics in reducing fecal and cloacal colonization of <i>Salmonella</i> spp. in chickens: a systematic review and meta-analysis

Researchers have studied probiotics and prebiotics as potential dietary therapies to address this condition. This study aims to assess the efficacy of prebiotics and probiotics in reducing <i>Salmonella</i> in broiler chickens’ faeces and cloacae. On 15 January 2024, we followed PRISMA procedures and searched five databases – PubMed, Web of Science, Scopus, Agricola, and VHL – for relevant papers. The inclusion criteria centred on studies that employed prebiotics, probiotics, or both as treatments for broiler chickens infected with <i>Salmonella</i>. The authors extracted the data and evaluated the risk of bias using the SYRCLE program. We conducted meta-analyses using a random-effects model, reporting the results as relative risk (RR) and standardised mean difference (SMD), accompanied by 95% confidence intervals. We examined twenty-nine studies, each with an average sample size of 201 broiler chicks. It took a lot longer for <i>Salmonella</i> to grow and shed when prebiotics, especially mannan-oligosaccharides (MOS) (SMD −1.43; 95% CI [−2.30, −0.56]; I² = 99%), were present. Probiotics helped a lot (SMD −1.93; 95% CI [−3.13, −0.46]; I² = 99%), but their overall effectiveness was affected by strain specificity and dose differences. The combination of prebiotics and probiotics tended to benefit but did not reach statistical significance (SMD −2.09; 95% confidence interval [−4.22, 0.04]). <i>Salmonella</i> prevalence decreased significantly in the experimental groups (RR 0.59; 95% CI [0.45, 0.79]; I² = 83%). Both prebiotics and probiotics reduce <i>Salmonella</i> colonisation and shedding in broiler hens’ faeces and cloacae, but prebiotics, especially MOS, have slightly stronger effects. Future research should try to standardise the intervention methods and how results are measured, focusing on faecal and cloacal colonisation.