Impact of postbiotics and probiotics on the cecal microbiome of broilers challenged with Salmonella

This study evaluated the effects of postbiotics on bacterial communication among lactic acid bacteria (LAB) and their antagonism against Salmonella. In vitro, the Spot-on-the-Lawn test showed that a single Enterococcus sp. strain produced the most effective postbiotic, increasing (P=0.05) the inhibition of 15 LAB strains against Salmonella. A single Pediococcus sp. strain exhibited the highest probiotic potential, with its antagonism enhanced (P=0.05) by 16 different postbiotics. In vivo, 240 day-of-hatch broilers were divided into six groups: A (negative control, basal diet), B (positive control, basal diet), C (basal diet + LAB A), D (LAB A + postbiotic), E (basal diet + LAB B), and F (basal diet + postbiotic). All groups except the negative control were challenged with S. Heidelberg at day 7. No significant reduction in cecal Salmonella was observed; prophylactic and therapeutic postbiotic treatments increased (P=0.05) Salmonella levels. Microbiome analysis showed high bacterial diversity in all groups (Simpson >0.8), significant differences in beta diversity after challenge (P=0.05), and similar relative abundance patterns, with Firmicutes predominating except in group F, which had higher Proteobacteria and Actinobacteria. These results highlight the complexity of the poultry microbiome and the importance of in vivo evaluation of postbiotics, which may yield different effects than in vitro studies.