Gut microbiome-produced metabolites in pigs: a review on their biological functions and the influence of probiotics

Abstract

The gastrointestinal tract is a complex ecosystem that contains a large number of microorganisms with different metabolic capacities. Modulation of the gut microbiome can improve the growth and promote health in pigs. Crosstalk between the host, diet, and the gut microbiome can influence the health of the host, potentially through the production of several metabolites with various functions. Short-chain and branched-chain fatty acids, secondary bile acids, polyamines, indoles, and phenolic compounds are metabolites produced by the gut microbiome. The gut microbiome can also produce neurotransmitters (such as γ-aminobutyric acid, catecholamines, and serotonin), their precursors, and vitamins. Several studies in pigs have demonstrated the importance of the gut microbiome and its metabolites in improving growth performance and feed efficiency, alleviating stress, and providing protection from pathogens. The use of probiotics is one of the strategies employed to target the gut microbiome of pigs. Promising results have been published on the use of probiotics in optimizing pig production. This review focuses on the role of gut microbiome-derived metabolites in the performance of pigs and the effects of probiotics on altering the levels of these metabolites.

Keywords: Gut microbiome; Metabolome; Microbiome-derived metabolite; Pig; Probiotics.

Fig. 1.. Microbiome-derived metabolites and their effects on swine health.

The gut microbiome, influenced by diet, produces various metabolites. SCFAs, bile acids, by-products of amino acid metabolism (BCFAs, polyamines, indolic compounds, and phenolic compounds), neurotransmitters, and vitamins are some of the metabolites produced by the gut microbiome. These metabolites are responsible for regulating intestinal health, immune function, metabolism, intestinal homeostasis, and cognitive function. However, high levels of some metabolites, such as ammonia and hydrogen sulfide, may not be beneficial to the host. Ultimately, the gut microbiome and its metabolites affect the growth performance, feed efficiency, and overall health of pigs. GABA, Y-aminobutyric acid; 5-HT, 5-hydroxytryptamine; BCFA, branched-chain fatty acid; SCFA, short-chain fatty acid; GPR/TGR, G-protein-coupled receptor; AhR, aryl hydrocarbon receptor; ATP, adenosine triphosphate; GLP-1, glucagon-like peptide 1; PYY, peptide YY; TNF, tumor necrosis factor; IL, interleukin; FXR, Farnesoid X receptor.