Enteric fermentation

Enteric fermentation

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Enteric fermentation is a digestive process by which carbohydrates are broken down by microorganisms into simple molecules for absorption into the bloodstream of an animal.

It is one of the factors in increased methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...


Ruminant animals are those that have a rumen
The rumen, also known as a paunch, forms the larger part of the reticulorumen, which is the first chamber in the alimentary canal of ruminant animals. It serves as the primary site for microbial fermentation of ingested feed...

. A rumen is a special stomach found in cows, sheep, and water buffalo
Bubalus is a genus of bovines, whose English name is buffalo. Species that belong to this genus are:* Subgenus Bubalus** Water Buffalo, Bubalus bubalis*** Carabao, Bubalus bubalis carabanesis...

 that enables them to eat tough plants and grains that monogastric
A monogastric organism has a simple single-chambered stomach, whereas ruminants have a four-chambered complex stomach. Examples of monogastric animals include omnivores such as humans, rats and pigs, carnivores such as dogs and cats, and herbivores such as Horses and rabbits. Herbivores with...

 animals, such as human
Humans are the only living species in the Homo genus...

s, dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...

s, and cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...

s, cannot digest.

Enteric fermentation occurs when methane (CH4) is produced in the rumen as microbial fermentation takes place. Over 200 species of microorganisms are present in the rumen, although only about 10% of these play an important role in digestion. Most of the CH4 byproduct is belched by the animal, however, a small percentage of CH4 is also produced in the large intestine
Large intestine
The large intestine is the third-to-last part of the digestive system — — in vertebrate animals. Its function is to absorb water from the remaining indigestible food matter, and then to pass useless waste material from the body...

 and passed out as flatulence.

Methane emissions are an important contribution to global greenhouse gas emmissions. The IPCC reports that methane is more than twenty times as effective as CO2 at trapping heat in the atmosphere. In Australia ruminant animals account for over half of their green house gas contribution from methane. Australia has implemented a voluntary immunization program for cattle in order to help reduce flatulence
Flatulence is the expulsion through the rectum of a mixture of gases that are byproducts of the digestion process of mammals and other animals. The medical term for the mixture of gases is flatus, informally known as a fart, or simply gas...

-produced CH4.

Enteric fermentation is the second largest anthropogenic source of methane emissions in the United States from 2000 through 2009. In 2007, methane emissions from enteric fermentation were 2.5% of net greenhouse gases produced in the United States at 139 teragram
Teragram may refer to:* 1012 grams, equivalent to a megatonne. See Orders of magnitude * Teragram Corporation...

s of carbon dioxide equivalents (Tg CO2) out of a total net emission of 5618 Tg C)2.

Un-cited References

  1. M. J. Gibbs and R. A. Leng, "Methane Emissions From Livestock", Methane And Nitrous Oxide, Proceedings Of The International IPCC Workshop, Amersfoort, The Netherlands, pp. 73-79, February 1993.
  2. State Workbook: Methodology For Estimating Greenhouse Gas Emissions, EPA 230-B-92-002, U. S. Environmental Protection Agency, Office of Policy, Planning and Evaluation, Washington, DC, 1995.
  3. International Anthropogenic Methane Emissions: Estimates for 1990, EPA-230-R-93-010. U. S. Environmental Protection Agency, Global Change Division, Office of Air and Radiation, Washington, DC, 1994.
  4. P. Crutzen, et al., Methane Production By Domestic Animals, Wild Ruminants, Other Herbivorous Fauna, and Humans, Tellus, 38B(3-4): 271-284, 1986.
  5. Anthropogenic Methane Emissions In The United States: Estimates For 1990, Report to Congress, U. S. Environmental Protection Agency, Office of Air and Radiation, Washington, DC, 1993.
  6. Greenhouse Gas Inventory Workbook, Intergovernmental Panel On Climate Change/Organization For Economic Cooperation And Development, Paris, France, pp. 4.1-4.5, 1995.