Preventive effects of synbiotic supplementation against Salmonella Enteritidis infection in broiler chickens

The restriction of antibiotics as growth promoters in poultry has intensified the search for alternative strategies to control enteric pathogens. This study aimed to develop a multi-strain probiotic composed of Enterococcus faecium CRL 1385, Ligilactobacillus salivarius subsp. salivarius CRL 1417, and Lactobacillus crispatus CRL 1453, formulate a synbiotic by combining this mixture with raffinose and molasses, and evaluate their preventive efficacy against Salmonella infection in broiler chicks. Strain compatibility was assessed using a well-diffusion assay with cell-free supernatants, confirming absence of antagonism among strains. In vitro co-culture assays demonstrated a clear bactericidal effect, with inactivation of Salmonella Enteritidis PT4 1222 and Salmonella Gallinarum INTA 91/A1. Ex vivo assays using intestinal explants showed that pre-treatment with probiotic or synbiotic formulations significantly reduced Salmonella adhesion, suggesting that the primary protective mechanism involved inhibition of pathogen attachment to epithelial surfaces. For in vivo evaluation, chicks received daily treatments from day 1 post-hatch and were challenged via crop injection on day 3. Synbiotic administration significantly reduced S. Enteritidis infection rates (30% vs. 100% in controls), while all treatments failed to reduce S. Gallinarum prevalence. These findings highlight the potential of early-life synbiotic administration as a sustainable strategy to prevent S. Enteritidis infections in poultry.