Submitted to: Encyclopedia of Animal Science
Publication Type: Book / Chapter
Publication Acceptance Date: June 25, 2003
Publication Date: November 1, 2004
Citation: Wells, J., Varel, V.H. 2005. Gi tract: Animal/microbial symbiosis. In: Pond, W.G., Bell, A.W., editors. Encyclopedia of Animal Science. Marcel Dekker,Inc., New York, NY. p. 449-452. Technical Abstract: The gastrointestinal tract is indispensable for the animal's well-being. Food is consumed through the mouth and digested by host enzymes in the stomach and small intestine, and nutrients are extracted and absorbed in the small and large intestines. Bacteria are ubiquitous in nature and the presence of bacteria in the gastrointestinal system is common. In this nutrient-rich environment, microorganisms can colonize and grow, and as a result, numerous interactions (symbioses) between microorganisms and the animal exist that impact the health and well-being of the host animal. Interactions that negatively impact the host animal are defined as being parasitic and include many pathogens, whereas positive impacts to the host are defined as being mutualistic. Most host/microbial interactions have not been demonstrated to be positive or negative to the host, and these are commonly referred as commensal. However, using advances in molecular techniques and better understanding of complex biological interactions, scientists are just starting to understand the complexities of these relationships and their implications. In the future, animal diets and supplementation may be adjusted to exploit or hinder certain animal/microbial interaction(s).