Chicken intestinal microbiome: Development and function

Abstract

Chicken ceca contain an immense number of microorganisms collectively known as the microbiome. This community is now recognized as an essential component of the intestinal ecosystem and referred to as a metabolic organ exquisitely tuned to the host’s physiology. These functions include the ability to process otherwise indigestible components of the feed, converting them into energy and body mass. The gut microbiome can also affect intestinal morphology and modulate the development and function of the immune system. This microbiota contains a rich collection of genes encoding enzymes necessary for decomposition of dietary polysaccharides and oligosaccharides, nitrogen metabolism, fatty acid and lipid metabolism, and pathways involved in a hydrogen sink. Chickens, like most animals, lack the genes for glycoside hydrolase, polysaccharide lyase, and carbohydrate esterase enzymes that are necessary to facilitate the degradation of non-starch polysaccharides. During the decomposition of dietary polysaccharides, bacteria produce short-chain (volatile) fatty acids (SCFAs), such as acetic, propionic and butyric acid. These SCFASs are absorbed transepithelially and serve as a source of energy for the host. The accumulation of molecular hydrogen released during fermentation leads to fermentation slowdown or to the production of less energy-efficient substances, such as ethanol, butyrate and propionate. The presence of bacteria that act as a hydrogen sink results in a switch to the more productive fermentation into acetate and increased production of SCFAs. Such activity could lead to a significant improvement in poultry production and the associated economics.