Phytobiotics as potential regulators of the gut microbiome composition and functional activity in broiler chickens - a mini-review

The efficiency of raising broiler chickens directly depends on the functional state of the gastrointestinal tract (N. Abdelli et al., 2021). The gut microbiome plays a key role in modulating the immune system and regulating digestive function. The relationship between diet and taxonomic profile is of particular interest to functional foods that have a positive effect on the microbiome (S. Khan et al., 2020). Metabolites synthesized by intestinal microorganisms serve as the main modulators of cross-communication between the host and the microbiome. Among these are short-chain fatty acids, tryptamine, conjugated linoleic acids, indole and its derivatives, as well as bile acids (S.A. Lee et al., 2017; S. Khan et al., 2020). Consequently, the microbiome is a fundamental link in maintaining productive interactions between the host and the intestine (S.A. Lee et al., 2017). Phytobiotics (FB) serve as a safe and effective alternative to feed antibiotics (M. Kikusato et al., 2021). The purpose of this review is to systematize information on the effectiveness of FB as potential regulators of the intestinal microbiome of broiler chickens. The beneficial functions of plant extracts mainly depend on their specific bioactive components (organic acids, polysaccharides, flavones), which can be synthesized as antimicrobial agents against pathogenic microorganisms (O.A. Bagno et al., 2018; J.J. Flees et al., 2021). It is known that the mechanism of action of FB consists in the destruction of the membrane of pathogenic microorganisms, modification of the cell surface with a change in virulence, stimulation of the immune system (S. Diaz-Sanchez et al., 2015). The contact of the microbiome and phytochemicals is a two-way process in which bacteria metabolize polyphenols into simpler metabolites, in turn, polyphenols affect the population of intestinal microorganisms, leading to a shift in metabolic activity (Y. Iqbal et al., 2020). FB control the growth and taxonomic composition of the intestinal microbiome, since phytochemicals, like prebiotics, have a positive effect on the state of the gastrointestinal tract even with minimal absorption in the small intestine (J. Martel et al., 2020). The feeding of phytochemicals is associated with high productivity indicators. It was found that the addition of the FB diet has a positive effect on the state of the metabolic activity of the organism and an increase in its adaptive potential, which is caused by the activation of the expression of certain genes ( IL6 and BPIFB3 ) in both infected and uninfected birds (G.Y. Laptev et al., 2021). Plant compounds can not only directly improve the health of broiler chickens, but also modulate the microbiota of the gastrointestinal tract and enhance the stimulating effect of productivity (O.A. Bagno et al., 2018). A review of the studies conducted on this topic demonstrates contradictory results. At this stage, it is important to understand the dynamics of the complex relationship between the environment, the host and the microbiome. Additional studies of the mechanisms of action of FB on the ecosystem of the gastrointestinal tract of broilers are needed.