Gut health in poultry.

Abstract Although the gastrointestinal tract is frequently described simply as 'the gut', it is actually made up of: (1) an epithelium; (2) a diverse and robust immune arm, which contains most of the immune cells in the body; and (3) the commensal bacteria, which contain more cells than are present in the entire host organism. Understanding of the crosstalk between ALL of these interrelated components of the gut is what cumulatively makes the gut the basis for the well-being of animals and the motor that drives their performance. Optimal gut health is of vital importance to the performance of production animals and is synonymous in animal production industries with animal health. There does appear to be a direct relationship between animal performance and a 'healthy' gut, there is no clear definition that includes all the physiological functions of the intestinal tract, including nutrient digestion and absorption, host metabolism and energy generation, a stable microbiome, mucus layer development, barrier function and mucosal immune responses. The most basic function of the gut is regulating physiological homeostasis that provides the host the ability to withstand infectious and non-infectious stressors. This review updates our understanding of the interactions between the diverse physiological features of the gut and emphasizes the extent of areas encompassed by gut health and the ability to regulate animal production.