Submitted to: Encyclopedia of Animal Science
Publication Type: Book / Chapter
Publication Acceptance Date: November 18, 2003
Publication Date: November 1, 2004
Citation: Varel, V.H., Wells, J. 2005. Lower digestive tract microbiology. In: Pond, W.G., Bell, A.W., editors. Encyclopedia of Animal Science. Marcel Dekker,Inc., New York, NY. p. 585-587. Technical Abstract: The lower digestive tract of animals is often referred to as the hindgut and normally denotes the large intestine which includes the cecum, colon, and rectum. The cecum is a branch from the junction of the small intestine and colon. There is a great diversity among animals in hindgut morphology, mainly in relation to diet of the animal. Carnivores have a small hindgut and a cecum may be absent. However, herbivores, such as the horse, have a large hindgut capacity. The hindgut of nonruminant animals is the primary site for retention of food residues and endogenous substrates for microbial fermentation. Conditions in the hindgut include a constant temperature, pH between 6.5 and 7.5, and low concentrations of oxygen, thus providing an environment for 10**9 to 10**11 microorganisms of up to 400 different species per gram of lumen contents. The microflora in the hindgut are critical to the well-being of an animal and provide nutrients (volatile fatty acids, vitamins) and protection from invading pathogens which constantly enter the open ecosystem with food and water. Currently, a large population of hindgut microorganisms is unknown (50%). New methods and techniques are needed to identify this large mass of diverse microorganisms. Once this capability is obtained, efforts are needed to follow the changing population of microorganisms on a short-term basis. This will allow us to more fully understand the significance of the microflora in animal growth efficiency and health.