A multi-species synbiotic improves growth performance in broiler chickens under conventional and enteric-challenge...

This study evaluated the efficacy of a multi-species synbiotic (SYN) comprising Bifidobacterium animalis, Enterococcus faecium, Ligilactobacillus salivarius, Limosilactobacillus reuteri, Pediococcus acidilactici, and fructo-oligosaccharides on broiler growth performance and footpad dermatitis across multiple trials conducted under conventional conditions and under experimentally induced enteric challenges. Challenge models included Eimeria spp. (with or without Clostridium perfringens) and Salmonella Enteritidis exposure, alongside comparisons against antibiotic growth promoters (AGP) or coccidiostats in selected studies. Fifteen independent studies contributed to the growth performance meta-analyses, of which three also contributed to the footpad dermatitis analysis. The analysis included trials from 2011 to 2023 with well-defined designs, duration ≥40 days, and reported sample sizes and standard deviations, categorizing them into conventional studies, enteric challenges (Eimeria spp. ± C. perfringens or Salmonella Enteritidis), and comparisons with AGP or coccidiostats. Meta-analysis results, corrected by Hedges' g, showed standardized mean differences (SMD) indicating medium effect sizes for body weight (BW, SMD = 0.74, P < 0.001), average daily gain (ADG, SMD = 0.59, P = 0.003), and feed conversion ratio (FCR, SMD = -0.56, P < 0.001) in broilers under conventional conditions. In challenged birds under experimental conditions, SYN exhibited medium to large effects on BW (SMD = 0.90, P = 0.007), ADG (SMD = 1.26, P = 0.002) and FCR (SMD = -0.56, P = 0.006), significantly outperforming untreated controls. Moreover, growth performance did not differ significantly between SYN and AGP or coccidiostat treatments in the available trials. SYN supplementation was associated with lower odds of footpad dermatitis (OR = 0.52; 95% CI = [0.28, 0.98]; P = 0.046), although heterogeneity was substantial. These results demonstrate that SYN supplementation enhances broiler growth performance, while the pooled footpad dermatitis analysis indicated lower odds of lesions. These findings suggest that SYN may have potential within strategies aimed at reducing reliance on antimicrobial growth promoters.