Home      Discussion      Topics      Dictionary      Almanac
Signup       Login
Ruminant

Ruminant

Overview
A ruminant is a mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

 of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...

, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud
Cud
Cud is a portion of food that returns from a ruminant's stomach in the mouth to be chewed for the second time. More accurately, it is a bolus of semi-degraded food regurgitated from the reticulorumen of a ruminant. Cud is produced during the physical digestive process of rumination, or "chewing the...

, and chewing it again. The process of rechewing the cud to further break down plant matter and stimulate digestion is called "ruminating".

There are about 150 species of ruminants which include both domestic and wild species.
Discussion
Ask a question about 'Ruminant'
Start a new discussion about 'Ruminant'
Answer questions from other users
Full Discussion Forum
 
Unanswered Questions
Encyclopedia
A ruminant is a mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

 of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...

, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud
Cud
Cud is a portion of food that returns from a ruminant's stomach in the mouth to be chewed for the second time. More accurately, it is a bolus of semi-degraded food regurgitated from the reticulorumen of a ruminant. Cud is produced during the physical digestive process of rumination, or "chewing the...

, and chewing it again. The process of rechewing the cud to further break down plant matter and stimulate digestion is called "ruminating".

There are about 150 species of ruminants which include both domestic and wild species. Ruminating mammals include cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...

, goat
Goat
The domestic goat is a subspecies of goat domesticated from the wild goat of southwest Asia and Eastern Europe. The goat is a member of the Bovidae family and is closely related to the sheep as both are in the goat-antelope subfamily Caprinae. There are over three hundred distinct breeds of...

s, sheep, giraffe
Giraffe
The giraffe is an African even-toed ungulate mammal, the tallest of all extant land-living animal species, and the largest ruminant...

s, bison
Bison
Members of the genus Bison are large, even-toed ungulates within the subfamily Bovinae. Two extant and four extinct species are recognized...

, moose
Moose
The moose or Eurasian elk is the largest extant species in the deer family. Moose are distinguished by the palmate antlers of the males; other members of the family have antlers with a dendritic configuration...

, elk
Elk
The Elk is the large deer, also called Cervus canadensis or wapiti, of North America and eastern Asia.Elk may also refer to:Other antlered mammals:...

, yak
Yak
The yak, Bos grunniens or Bos mutus, is a long-haired bovine found throughout the Himalayan region of south Central Asia, the Tibetan Plateau and as far north as Mongolia and Russia. In addition to a large domestic population, there is a small, vulnerable wild yak population...

s, water buffalo
Bubalus
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...

, deer
Deer
Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...

, camel
Camel
A camel is an even-toed ungulate within the genus Camelus, bearing distinctive fatty deposits known as humps on its back. There are two species of camels: the dromedary or Arabian camel has a single hump, and the bactrian has two humps. Dromedaries are native to the dry desert areas of West Asia,...

s, alpaca
Alpaca
An alpaca is a domesticated species of South American camelid. It resembles a small llama in appearance.Alpacas are kept in herds that graze on the level heights of the Andes of southern Peru, northern Bolivia, Ecuador, and northern Chile at an altitude of to above sea level, throughout the year...

s, llama
Llama
The llama is a South American camelid, widely used as a meat and pack animal by Andean cultures since pre-Hispanic times....

s, antelope
Antelope
Antelope is a term referring to many even-toed ungulate species indigenous to various regions in Africa and Eurasia. Antelopes comprise a miscellaneous group within the family Bovidae, encompassing those old-world species that are neither cattle, sheep, buffalo, bison, nor goats...

, pronghorn
Pronghorn
The pronghorn is a species of artiodactyl mammal endemic to interior western and central North America. Though not an antelope, it is often known colloquially in North America as the prong buck, pronghorn antelope, or simply antelope, as it closely resembles the true antelopes of the Old World and...

, and nilgai
Nilgai
The nilgai , sometimes called nilgau, is an antelope, and is one of the most commonly seen wild animals of central and northern India and eastern Pakistan; it is also present in parts of southern Nepal. The mature males appear ox-like and are also known as blue bulls...

.
Taxonomically, the suborder Ruminantia
Ruminantia
Ruminantia includes many of the well-known large grazing or browsing mammals: among them cattle, goats, sheep, deer, and antelope. All members of the Ruminantia are ruminants: they digest food in two steps, chewing and swallowing in the normal way to begin with, and then regurgitating the...

 includes all those species except the camels, llamas, and alpacas, which are Tylopoda
Tylopoda
Tylopoda is a suborder of terrestrial herbivorous even-toed ungulates belonging to Artiodactyla. They are extant in the wild in their native ranges of South America and Asia, while Australian feral camels are an introduced species. The group has a long fossil history in North America and Europe...

. Therefore, the term 'ruminant' is not synonymous with Ruminantia
Ruminantia
Ruminantia includes many of the well-known large grazing or browsing mammals: among them cattle, goats, sheep, deer, and antelope. All members of the Ruminantia are ruminants: they digest food in two steps, chewing and swallowing in the normal way to begin with, and then regurgitating the...

. The word "ruminant" comes from the Latin ruminare, which means "to chew over again".

Explanation



The primary difference between a ruminant and non-ruminant (called monogastric
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...

s, such as humans, dogs, and pigs) is that ruminants have a four-compartment stomach. The four parts of the stomach are rumen, reticulum, omasum, and abomasum. In the first two chambers, the rumen and the reticulum, the food is mixed with saliva and separates into layers of solid and liquid material. Solids clump together to form the cud or bolus
Bolus
-Medicine:* Bolus , the administration of a drug, medication or other substance in the form of a single, large dose* Bolus , a tissue equivalent substance used in radiation therapy...

.

The cud is then regurgitated, chewed slowly to completely mix it with saliva and to break down the particle size. Fiber, especially cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

 and hemi-cellulose, is primarily broken down into the three volatile fatty acids
Volatile fatty acids
Volatile fatty acids are fatty acids with a carbon chain of six carbons or fewer. They are now usually referred to as short-chain fatty acids .They can be created through fermentation in the intestine.Examples include:* Acetic acid...

, acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

, propanoic acid and beta-hydroxybutyric acid, in these chambers by microbes (bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, archaea
Archaea
The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

, protozoa
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...

, and fungi). Protein and non-structural carbohydrate (pectin
Pectin
Pectin is a structural heteropolysaccharide contained in the primary cell walls of terrestrial plants. It was first isolated and described in 1825 by Henri Braconnot...

, sugars, starches) are also fermented.

Even though the rumen and reticulum have different names they represent the same functional space as digesta can move back and forth between them. Together these chambers are called the reticulorumen. The degraded digesta, which is now in the lower liquid part of the reticulorumen, then passes into the next chamber, the omasum, where water and many of the inorganic mineral elements are absorbed into the blood stream.

After this the digesta is moved to the true stomach, the abomasum. The abomasum is the direct equivalent of the monogastric stomach (for example that of the human or pig), and digesta is digested here in much the same way. Digesta is finally moved into the small intestine, where the digestion and absorption of nutrients occurs. Microbes produced in the reticulorumen are also digested in the small intestine. Fermentation continues 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...

 in the same way as in the reticulorumen.

Almost all the glucose produced by the breaking down of cellulose and hemi-cellulose is used by microbes in the rumen, and as such ruminants usually absorb little glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

 from the small intestine
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...

. Rather, ruminants' requirement for glucose (for brain function and lactation if appropriate) is made by the liver from propionate, one of the volatile fatty acids made in the rumen.

Classification


Hofmann and Stewart divided ruminants into three major categories based on their feed type and feeding habits: concentrate selectors; intermediate types; and grass/roughage eaters, with the assumption that feeding habits in ruminants cause morphological differences in their digestive systems, including salivary glands, rumen size, and rumen papillae.

There are also pseudo-ruminants having three-compartment stomach instead of four like ruminants. Monogastric
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 Guinea pigs, horses and rabbits are not ruminants as they have a simple single-chambered stomach and digest cellulose via an enlarged cecum
Cecum
The cecum or caecum is a pouch, connecting the ileum with the ascending colon of the large intestine. It is separated from the ileum by the ileocecal valve or Bauhin's valve, and is considered to be the beginning of the large intestine. It is also separated from the colon by the cecocolic...

 allowing the easy digestion of fibrous materials. Such animals are called hindgut fermenters
Hindgut fermentation
Hindgut fermentation is a digestive process seen in monogastric herbivores, animals with a simple, single-chambered stomach. Cellulose is digested with the aid of symbiotic bacteria. The microbial fermentation occurs in the digestive organs that follow the small intestine, namely the large...

.

Abundance, distribution, and domestication


Wild ruminants number at least 75 million and are native to all continents except Australia and Antarctica. Nearly 90% of all species are found in Eurasia and Africa alone. Species inhabit a wide range of climates (from tropic to arctic) and habitats (from open plains to forests).

The population of domestic ruminants is greater than 3.5 billion, with cattle, sheep, and goats accounting for about 95% of the total population. Goats were domesticated in the Near East at approximately 8,000 B.C. Most other species were domesticated by 2,500 B.C., either in the Near East or southern Asia.

Ruminant physiology


Ruminating animals have various physiological features which enable them to survive in nature. One feature of ruminants is their continuously growing teeth. During grazing, the silica content in forage
Forage
Forage is plant material eaten by grazing livestock.Historically the term forage has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used more loosely to include similar plants cut for fodder and carried to the animals, especially...

 causes abrasion of teeth. Abrasion of the teeth is compensated by continuous tooth growth throughout the ruminant's life, as opposed to humans or other non-ruminants whose teeth stop growing after a particular age. Ruminants do not have upper incisors, instead they have a thick dental pad to thoroughly bite food.

Rumen microbiology


Vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s lack the ability to hydrolyse beta [1-4] glycosidic bond of plant cellulose due to the lack of an enzyme celulase
Cellulase
400px|thumb|right|alt = Colored dice with checkered background|Ribbon representation of the Streptomyces lividans beta-1,4-endoglucanase catalytic domain - an example from the family 12 glycoside hydrolases...

. Thus ruminants must completely depend upon the microbial flora, present in rumen or hindgut, so as to digest cellulose. Digestion of food in rumen is primarily carried out by the rumen microflora which contain dense populations of several species of bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, protozoa
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...

, sometimes yeasts and fungi. It is estimated that 1mm of rumen contains 10-50 billion bacteria, 1 million protozoa and several yeasts, fungi.

As the environment inside a rumen is anaerobic
Anaerobic
Anaerobic is a word which literally means without oxygen, as opposed to aerobic.In wastewater treatment the absence of oxygen is indicated as anoxic; and anaerobic is used to indicate the absence of a common electron acceptor such as nitrate, sulfate or oxygen.Anaerobic may refer to:*Anaerobic...

, most of these microbial species are obligate
Obligate anaerobe
Obligate anaerobes are microorganisms that live and grow in the absence of molecular oxygen; some of these are killed by oxygen. -Metabolism:...

 or facultative
Facultative anaerobic organism
A facultative anaerobic organism is an organism, usually a bacterium, that makes ATP by aerobic respiration if oxygen is present but is also capable of switching to fermentation...

 anaerobes which can decompose complex plant material such as cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

, hemicellulose
Hemicellulose
A hemicellulose is any of several heteropolymers , such as arabinoxylans, present along with cellulose in almost all plant cell walls. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength...

, starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...

, proteins. Hydrolysis of cellulose results in sugars which are further fermentated to acetate, lactate, propionate, butyrate, carbon dioxide and methane.

During grazing, ruminants produce large amount of saliva. Estimates are within 100 to 150 litres of saliva per day for an adult cow. The role of saliva is to provide ample fluid for rumen fermentation and as a buffering agent. Rumen fermentation produces large amounts of organic acids and thus maintaining the appropriate pH of rumen fluids is a critical factor in rumen fermentation.

Tannin toxicity in ruminant animals


Tannin
Tannin
A tannin is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids.The term tannin refers to the use of...

s are phenolic compounds
Polyphenol
Polyphenols are a structural class of natural, synthetic, and semisynthetic organic chemicals characterized by the presence of large multiples of phenol structural units...

 that are commonly found in plants. These compounds play a role in protection from predation, as well as growth regulation, when they are digested by herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

s. Found in the leaf, bud, seed, root, and stem tissues, tannins are widely distributed in many different species of plants. Tannins are separated into two classes: hydrolysable tannins and condensed tannins. Depending on their concentration and nature either class can have adverse or beneficial effects. When ruminants digest some plants, they acquire a surplus of tannins and rumen microbes do not have the enzymatic ability for degrading condensed tannins. In fact, digestion of tannins by ruminants in large amounts can reduce the activity and the proliferation of ruminal microorganisms reducing ruminal biohydrogenation.

Tannins can also precipitate proteins and inhibit the absorption of nutrients. Very high levels of tannin intake can produce toxicity
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...

 that can even cause death. Animals normally consuming tannin-rich plants can develop defensive mechanisms against tannins, such as the strategic deployment of lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...

s and extracellular
Extracellular
In cell biology, molecular biology and related fields, the word extracellular means "outside the cell". This space is usually taken to be outside the plasma membranes, and occupied by fluid...

 polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

s that have a high affinity to binding to tannins. These mechanisms prevent tannins from causing adverse effects on rumen microbes.

Religious importance


In Abrahamic religions, a distinction between clean and unclean animals approximately falls according to whether the animal ruminates. The Law of Moses
613 mitzvot
The 613 commandments is a numbering of the statements and principles of law, ethics, and spiritual practice contained in the Torah or Five Books of Moses...

 in the Bible
Bible
The Bible refers to any one of the collections of the primary religious texts of Judaism and Christianity. There is no common version of the Bible, as the individual books , their contents and their order vary among denominations...

 allowed only the eating of animals that had cloven hooves and "that chew the cud", a stipulation preserved to this day in the Jewish laws of Kashrut
Kashrut
Kashrut is the set of Jewish dietary laws. Food in accord with halakha is termed kosher in English, from the Ashkenazi pronunciation of the Hebrew term kashér , meaning "fit" Kashrut (also kashruth or kashrus) is the set of Jewish dietary laws. Food in accord with halakha (Jewish law) is termed...

.

Other uses


The verb to ruminate has been extended metaphor
Metaphor
A metaphor is a literary figure of speech that uses an image, story or tangible thing to represent a less tangible thing or some intangible quality or idea; e.g., "Her eyes were glistening jewels." Metaphor may also be used for any rhetorical figures of speech that achieve their effects via...

ically to mean to ponder thoughtfully or to meditate
Meditation
Meditation is any form of a family of practices in which practitioners train their minds or self-induce a mode of consciousness to realize some benefit....

on some topic. Similarly, ideas may be chewed on or digested. Chew the (one's) cud is to reflect or meditate. In psychology, "rumination"
Rumination (psychology)
Rumination is a way of responding to distress that involves repetitively focusing on the symptoms of distress, and on its possible causes and consequences. Rumination is more common in people who are pessimistic, neurotic, and who have negative attributional styles. The tendency to ruminate is a...

 refers to a pattern of thinking, and is unrelated to digestive physiology.

Ruminants and climate change


Methane
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...

 has 23 times the warming potential of carbon dioxide and its production by ruminants may contribute to a greenhouse effect
Greenhouse effect
The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface, energy is transferred to the surface and the lower atmosphere...

 or climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

. Methane production by animals, principally ruminants, is estimated 15-20% global production of methane. The rumen is the major site of methane production in ruminants.

External links