Table 1 The composition of the microbiota in broiler chickens, considering the sections of the digestive tract and the compounds produced by the bacteria
From: State of the art in research on the gut-liver and gut-brain axis in poultry
Bacteria | Place of occurrence in the digestive system | Compounds produced by bacteria | Compounds description | Reference |
|---|---|---|---|---|
Bifidobacterium | Caeca, crop, gizzard, esophagus, proventriculus | Vitamins K, B1, and B2, lactic acid | Lactic acid reduces pH, facilitates digestion and absorption of metabolic products, improves intestinal peristalsis, reduces cholesterol levels, and prevents diarrhea and indigestion. | [19] |
Clostridium | Caeca, ileum | Propionate, butyrate | The ability to strongly bind propionate to Olfr78 receptors and G-protein-coupled receptor 41 (GPR41) is associated with the hypotensive effect of propionate, while Olfr78, in combination with propionate, increases blood pressure. Propionate, by interacting with the GPR43 protein present on adipose tissue cells and intestinal endocrine cells, stimulates the secretion of the intestinal hormones PYY (peptide YY) and GLP-1 (glucagon-like peptide-1), which consequently reduces the appetite and slows down the absorption of glucose. | |
Enterobacter | Caeca, crop, gizzard, ileum | Histamine | The action of histamine is related to H receptors (H1-H4). It acts as a neurotransmitter and local hormone, modulates the work of the stomach, and heart work, smooths muscle contractions and circadian rhythm, and maintains body temperature. | [22] |
Escherichia coli | Ileum | Hydrogen sulfide | It is a toxic gas secreted by the E. coli in the ileum. Excess H2S is a problem in commercial poultry houses; exposure of the hen’s internal organs to it causes immune dysregulation in hens. | [23] |
Faecalibacterium | Caeca, large intestine | Butyrate | Its reduction contributes to a decrease in the integrity of the gastrointestinal barrier. The increase in the abundance of butyrate restores bone density and osteocyte activity and reduces inflammation in the skeletal system. | [24] |
Lactobacillus | Caeca, crop, gizzard, esophagus, ileum, proventriculus | Acetylcholine, serotonin, dopamine, gamma-aminobutyric acid (GABA) | Vagus nerve GABA receptor expression and hyperpolarization of enteric nervous system neurons affect pain sensation by the nervous system. Serotonin, as a neurotransmitter and tissue hormone, participates in the transmission of impulses between cells of the nervous system; it affects emotional states, concentration, and memory. | [25] |