Abstract: Biologically active substances such as short-chain fatty acids (SCFAs) and bile acids produced by the metabolism of many microorganisms are present in animals.Among them,SCFAs are mainly produced by the fermentation of dietary fiber bacteria,which can be used as both an energy source for intestinal mucosal cells and a signaling substance.SCFAs can not only regulate the intestinal flora and enhance the intestinal barrier function,but also participate in the regulation of the nervous system through various pathways.Therefore,SCFAs are considered to be important factors affecting host health.In the context of a total antibiotic ban,finding suitable antibiotic alternatives has become a hot research topic.Exogenous addition of appropriate amounts of SCFAs can improve the enrichment of beneficial bacteria in the animal gut,increase the expression of tight junction proteins,and enhance the immune function of the body.In addition,SCFAs have some therapeutic potential in the study of central nervous system diseases,such as autism and depression.Most of SCFAs produced by gut microbial metabolism are acetic acid,propionic acid and butyric acid.Currently,the studies on SCFAs are dominated by butyric acid,while the studies on the combined effects of mixtures of SCFAs are relatively few,and the application areas are yet to be expanded.The authors summarized the potential effects of SCFAs on animal intestinal health and gut-brain signaling as well as the possible regulatory mechanisms,which provides a theoretical basis for the development of SCFAs as an exogenous additive or drug to be promoted in the modulation of animal health and disease treatment and other applications.

Key words: short-chain fatty acids; intestinal flora; intestinal barrier; gut-brain signaling