Quorum sensing inhibitors (QSIs) are an attractive alternative to antibiotic growth promoters in farmed animal nutrition. The goal of the study was the diet supplementation of Arbor Acres chickens with quercetin (QC), vanillin (VN), and umbelliferon (UF), which are plant-derived QSIs preliminarily showing cumulative bioactivity. Chick cecal microbiomes were analyzed by 16s rRNA sequencing, inflammation status was assessed by blood sample analyses, and zootechnical data were summarized in the European Production Efficiency Factor (EPEF). When compared to the basal diet control group, a significant increase in the Bacillota:Bacteroidota ratio in the cecal microbiome was found in all experimental subgroups, with the highest expression > 10 at VN + UV supplementation. Bacterial community structure in all experimental subgroups was enriched with Lactobacillaceae genera and also changed in the abundance of some clostridial genera. Indices of richness, alpha diversity, and evenness of the chick microbiomes tended to increase after dietary supplementation. The peripheral blood leukocyte content decreased by 27.9–45.1% in all experimental subgroups, likely due to inflammatory response reduction following beneficial changes in the cecal microbiome. The EPEF calculation showed increased values in VN, QC + UF, and, especially, VN + UF subgroups because of effective feed conversion, low mortality, and broiler weight daily gain.
Coumarins are class of natural aromatic compounds based on benzopyrones (2H-1-benzopyran-2-ones). They are identified as secondary metabolites in about 150 different plant species. The ability of coumarins to inhibit cell-to-cell communication in bacterial communities (quorum sensing; QS) has been previously described. Coumarin and its derivatives in plant extracts are often found together with other small molecules that show anti-QS properties too. The aim of this study was to find the most effective combinations of coumarins and small plant-derived molecules identified in various plants extracts that inhibit QS in Chromobacterium violaceum ATCC 31532 violacein production bioassay. The coumarin and its derivatives: 7-hydroxycoumarin, 7.8-dihydroxy-4-methylcoumarin, were included in the study. Combinations of coumarins with gamma-octalactone, 4-hexyl-1.3-benzenediol, 3.4.5-trimethoxyphenol and vanillin, previously identified in oak bark (Quercus cortex), and eucalyptus leaves (Eucalyptus viminalis) extracts, were analyzed in a bioassay. When testing two-component compositions, it was shown that 7.8-dihydroxy-4-methylcoumarin, 4-hexyl-1.3-benzendiol, and gamma-octalactone showed a supra-additive anti-QS effect. Combinations of all three molecules resulted in a three- to five-fold reduction in the concentration of each compound needed to achieve EC50 (half maximal effective concentration) against QS in C. violaceum ATCC 31532.
The prohibition of antibiotic drugs in animal husbandry to stimulate animal productivity has provoked an active study of alternative substances, including plant extracts. No less interesting for a detailed study of the extracts of plants Eucalyptus viminalis and Scutellaria baicalensis, as information about their effect on ruminant microbiome is extremely scarce. According to the results of phytochemical analysis, 14 small molecules were found in the extract of Scutellaria baicalensis. and 13 in the composition of the extract of the leaves of Eucalyptus viminalis. Analysis of metagenomic sequencing when plant extracts are included in the feed indicates a significant change in the rumen microbiome. The absence of Proteobacteria and Fibrobacteres phyla in the experimental groups, a decrease in the content of Bacteroidetes by 12.0–17.0% and an increase in Firmicutes (p<0.05) and Saccharibacteria (p<0.05) were noted. An increase in the class Clostridia (p<0.05), due to the family Ruminococcaceae (p<0.05) and the genus Ruminococaceace, was found. In the Bacteroidia class in all groups, the family Prevotellaceae, the genus Prevotella, prevailed in most of the groups. Additional inclusion in the diet of plant extracts of Eucalyptus viminalis and Scutellaria baicalensis have a significant impact on the rumen microbiome of the cattle, the taxonomic identification of microorganisms indicates the prevalence of phyloma Firmicutes, Clostridia class and the Ruminococcaceae family, which are responsible for the separation of imperfect migration. Further evaluation of plant matter is needed in the direction of the overall effect on fermentation of feed in the rumen.
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