Abstract
Short-chain fatty acids (SCFAs) are metabolites generated by bacterial fermentation of dietary fiber (DF) in the hindgut. SCFAs are mainly composed of acetate, propionate and butyrate. Many studies have shown that SCFAs play a significant role in the regulation of intestinal health in poultry. SCFAs are primarily absorbed from the intestine and used by enterocytes as a key substrate for energy production. SCFAs can also inhibit the invasion and colonization of pathogens by lowering the intestinal pH. Additionally, butyrate inhibits the expression of nitric oxide synthase (NOS), which encodes inducible nitric oxide synthase (iNOS) in intestinal cells via the PPAR-γ pathway. This pathway causes significant reduction of iNOS and nitrate, and inhibits the proliferation of Enterobacteriaceae to maintain overall intestinal homeostasis. SCFAs can enhance the immune response by stimulating cytokine production (e.g. TNF-α, IL-2, IL-6, and IL-10) in the immune cells of the host. Similarly, it has been established that SCFAs promote the differentiation of T cells into T regulatory cells (Tregs) and expansion by binding to receptors, such as Toll-like receptors (TLR) and G protein-coupled receptors (GPRs), on immune cells. SCFAs have been shown to repair intestinal mucosa and alleviate intestinal inflammation by activating GPRs, inhibiting histone deacetylases (HDACs), and downregulating the expression of pro-inflammatory factor genes. Butyrate improves tight-junction-dependent intestinal barrier function by promoting tight junction (TJ) assembly. In recent years, the demand for banning antibiotics has increased in poultry production. Therefore, it is extremely important to maintain the intestinal health and sustainable production of poultry. Taking nutrition strategies is important to regulate SCFA production by supplementing dietary fiber and prebiotics, SCFA-producing bacteria (SPB), and additives in poultry diet. However, excessive SCFAs will lead to the enteritis in poultry production. There may be an optimal level and proportion of SCFAs in poultry intestine, which benefits to gut health of poultry. This review summarizes the biological functions of SCFAs and their role in gut health, as well as nutritional strategies to regulate SCFA production in the poultry gut.
Highlights
Increasing evidence has revealed that the gut microbiota is a key contributor to health and gut homeostasis of the host
Research has indicated that 0.05% xylooligosaccharides simultaneously stimulate acetate and butyrate production in the cecum of laying hens, but the propionate content was not affected by xylooligosaccharides [124]. These findings suggest that the structure and chemical properties of dietary fibers are associated with the metabolism of the gut microbiota, and that specific feeding pattern and doses may impact SCFA production
The influence of dietary factors, through dietary interventions such as increasing dietary fiber, butyric acid, and acid-producing bacteria, can increase the SCFAs in the intestine, excessive SCFAs in the hindgut will promote the development of metabolic syndrome via the gut microbiota–brain–β-cell axis
Summary
Increasing evidence has revealed that the gut microbiota is a key contributor to health and gut homeostasis of the host. Butyrate as a preventive treatment can effectively decrease gut permeability characterized by reduced concentrations of D (–)-lactate in DSS-induced broilers, and this beneficial changes are closely related to restoration of tight junction function [56]. Regulation of SCFAs on the gut mechanical barrier is mainly through promoting the gene expression of relevant junction tight proteins, thereby reducing intestinal permeability and improving the animal’s gut barrier functions.
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