Physiologically, a
ruminant is a
mammalMammals are a class of vertebrate animals whose females are characterized by the possession of mammary glands while both males and females are characterized by sweat glands, hair, three middle ear bones used in hearing, and a neocortex region in the brain.Mammals are divided into three main...
of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first stomach, known as the
rumenThe 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...
, then regurgitating the semi-digested mass, now known as
cudCud 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". Ruminating mammals include
cattleCattle 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...
,
goatThe 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: both are in the goat-antelope subfamily Caprinae. There are over three hundred distinct breeds of...
s, sheep,
giraffeThe giraffe is an African even-toed ungulate mammal, the tallest of all land-living animal species, and the largest ruminant. It is covered in large, irregular patches of yellow to black fur separated by white, off-white, or dark yellowish brown background. The average mass for an adult male...
s,
bisonMembers of the genus Bison are large even-toed ungulates within the subfamily Bovinae. Two extant species and four extinct species are recognized...
,
yakThe yak is a long-haired bovine found throughout the Himalayan region of south Central Asia, the Tibetan Plateau and as far north as Mongolia. In addition to a large domestic population, there is a small, vulnerable wild yak population. In Tibetan, the word gyag refers only to the male of the...
s,
water buffaloBubalus 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...
,
deerDeer are the ruminant mammals forming the family Cervidae. They include for example Moose, Red Deer, Reindeer, Roe and Chital. Animals from related families within the order Artiodactyla are often also considered to be deer – these include muntjac and water deer...
,
camelCamels are even-toed ungulates within the genus Camelus. The dromedary or Arabian camel has a single hump, and the Bactrian camel has two humps. They are native to the dry desert areas of western Asia, and central and east Asia, respectively...
s,
alpacaAlpaca is a domesticated species of South American camelid. It resembles a small llama in superficial appearance.Alpacas are kept in herds that graze on the level heights of the Andes of Ecuador, southern Peru, northern Bolivia, and northern Chile at an altitude of to above sea-level, throughout...
s,
llamaThe llama is a South American camelid, widely used as a pack animal by the Incas and other natives of the Andes mountains. In South America llamas are still used as beasts of burden, as well as for the production of fiber and meat....
s,
wildebeestThe wildebeest , also called the gnu , is an antelope of the genus Connochaetes. It is a hooved mammal. Wildebeest is Dutch for wild beast....
,
antelopeAntelope is a term referring to many even-toed ungulate species found in the family Bovidae. The term does not refer to a monophyletic group, as not all members of Bovidae are considered antelope. Instead, the term refers to a ‘miscellaneous’ group within the family encompassing the species which...
,
pronghornThe Pronghorn , is a species of ungulate mammal native to interior western and central North America. Though not a true antelope, it is often known colloquially as the Prong Buck, Pronghorn Antelope or simply Antelope , as it closely resembles the true antelopes of the Old World and fills a similar...
, and
nilgaiThe Nilgai 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
RuminantiaThe biological suborder Ruminantia includes many of the well-known large grazing or browsing mammals: among them cattle, goats, sheep, deer, and antelope...
includes all those species except the camels, llamas, and alpacas, which are
TylopodaTylopoda is a suborder of terrestrial herbivorous even-toed ungulates belonging to Artiodactyla, endemic more as extinct genera to North America and Europe. They are extant in South America, Africa, and Asia...
.
Physiologically, a
ruminant is a
mammalMammals are a class of vertebrate animals whose females are characterized by the possession of mammary glands while both males and females are characterized by sweat glands, hair, three middle ear bones used in hearing, and a neocortex region in the brain.Mammals are divided into three main...
of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first stomach, known as the
rumenThe 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...
, then regurgitating the semi-digested mass, now known as
cudCud 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". Ruminating mammals include
cattleCattle 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...
,
goatThe 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: both are in the goat-antelope subfamily Caprinae. There are over three hundred distinct breeds of...
s, sheep,
giraffeThe giraffe is an African even-toed ungulate mammal, the tallest of all land-living animal species, and the largest ruminant. It is covered in large, irregular patches of yellow to black fur separated by white, off-white, or dark yellowish brown background. The average mass for an adult male...
s,
bisonMembers of the genus Bison are large even-toed ungulates within the subfamily Bovinae. Two extant species and four extinct species are recognized...
,
yakThe yak is a long-haired bovine found throughout the Himalayan region of south Central Asia, the Tibetan Plateau and as far north as Mongolia. In addition to a large domestic population, there is a small, vulnerable wild yak population. In Tibetan, the word gyag refers only to the male of the...
s,
water buffaloBubalus 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...
,
deerDeer are the ruminant mammals forming the family Cervidae. They include for example Moose, Red Deer, Reindeer, Roe and Chital. Animals from related families within the order Artiodactyla are often also considered to be deer – these include muntjac and water deer...
,
camelCamels are even-toed ungulates within the genus Camelus. The dromedary or Arabian camel has a single hump, and the Bactrian camel has two humps. They are native to the dry desert areas of western Asia, and central and east Asia, respectively...
s,
alpacaAlpaca is a domesticated species of South American camelid. It resembles a small llama in superficial appearance.Alpacas are kept in herds that graze on the level heights of the Andes of Ecuador, southern Peru, northern Bolivia, and northern Chile at an altitude of to above sea-level, throughout...
s,
llamaThe llama is a South American camelid, widely used as a pack animal by the Incas and other natives of the Andes mountains. In South America llamas are still used as beasts of burden, as well as for the production of fiber and meat....
s,
wildebeestThe wildebeest , also called the gnu , is an antelope of the genus Connochaetes. It is a hooved mammal. Wildebeest is Dutch for wild beast....
,
antelopeAntelope is a term referring to many even-toed ungulate species found in the family Bovidae. The term does not refer to a monophyletic group, as not all members of Bovidae are considered antelope. Instead, the term refers to a ‘miscellaneous’ group within the family encompassing the species which...
,
pronghornThe Pronghorn , is a species of ungulate mammal native to interior western and central North America. Though not a true antelope, it is often known colloquially as the Prong Buck, Pronghorn Antelope or simply Antelope , as it closely resembles the true antelopes of the Old World and fills a similar...
, and
nilgaiThe Nilgai 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
RuminantiaThe biological suborder Ruminantia includes many of the well-known large grazing or browsing mammals: among them cattle, goats, sheep, deer, and antelope...
includes all those species except the camels, llamas, and alpacas, which are
TylopodaTylopoda is a suborder of terrestrial herbivorous even-toed ungulates belonging to Artiodactyla, endemic more as extinct genera to North America and Europe. They are extant in South America, Africa, and Asia...
. Therefore, the term 'ruminant' is not synonymous with
RuminantiaThe biological suborder Ruminantia includes many of the well-known large grazing or browsing mammals: among them cattle, goats, sheep, deer, and antelope...
.
Explanation
The ruminant stomach consists of three fore-stomachs, which are the
rumenThe 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...
,
reticulumThe reticulum is the second chamber in the alimentary canal of a ruminant animal. Anatomically it is considered the smaller half of the reticulorumen along with the rumen....
, and
omasumThe omasum, also known as the bible, the fardel, the manyplies and the psalterium, is the third compartment of the stomach in ruminants...
, and a true stomach, the
abomasumThe abomasum, also known as the maw, and the rennet-bag, and the read, is the fourth and final stomach compartment in ruminants. It secretes rennet, an ingredient used in cheese creation....
. 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-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
celluloseCellulose 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 acidsVolatile fatty acids are fatty acids with a carbon chain of six carbons or fewer.They can be created through fermentation in the intestine.Examples include:* acetate* propionate* butyrate-External links:*...
,
acetic acidAcetic acid, CH
3COOH, also known as ethanoic acid, is an organic acid which gives vinegar its sour taste and pungent smell. It is a weak acid, in that it is only partially dissociated acid in aqueous solution...
,
propionic acidPropionic acid is a naturally-occurring carboxylic acid with chemical formula CH3CH2COOH. It is a clear liquid with a pungent odor...
and
butyric acidButyric acid , also known under the systematic name butanoic acid, is a carboxylic acid with the structural formula CH3CH2CH2-COOH. Salts and esters of butyric acid are known as butyrates or butanoates...
, in these chambers by microbes (
bacteriaThe bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
,
protozoaProtozoa or Cornelius protozoans Protozoa or Cornelius protozoans Protozoa or Cornelius protozoans (from Greek πρῶτον proton "first" and ζῷα zoa "animals"; singular protozoon; (the word "protozoan" is originally an adjective, used as a noun) are microorganisms classified as unicellular eukaryotes....
, and fungi). Protein and non-structural carbohydrate (
pectinPectin 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 reticulo-rumen are also digested in the small intestine. Fermentation continues in the
large intestineThe large intestine is the second to last part of the digestive system—the final stage of the alimentary canal is the anus —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 hemicellulose is used by microbes in the rumen, and as such ruminants usually absorb little
glucoseGlucose , a monosaccharide also known as - grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology. The living cell uses it as a source of energy and metabolic intermediate...
from the
small intestineIn vertebrates, the small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where the vast majority of digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large...
. 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 .
Religious importance
In Abrahamic religions, a distinction between clean and unclean animals approximately falls according to whether the animal ruminates. The
Law of MosesThe 613 Mitzvot are statements and principles of law and ethics contained in the Torah or Five Books of Moses...
in the
BibleThe Bible contains the central religious texts of Judaism and Christianity. Modern Judaism generally recognizes a single set of canonical books known as the Tanakh, or Hebrew Bible, as it is written almost entirely in the Hebrew language, with some small portions in Aramaic...
allowed only the eating of animals that had split hooves and "that chew the cud", a stipulation preserved to this day in the
KashrutKashrut 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"...
.
Other uses
The verb
to ruminate has been extended
metaphorA metaphor is a figure of speech concisely comparing two things, saying that one is the other. The English metaphor derives from the 16th c...
ically to mean
to thoughtfully ponder or
to meditateMeditation is used here as a broad term for practices done by a sole practitioner without much, if any, external aide, often for the purpose of self-transformation...
on some topic. Similarly, ideas may be
chewed on or
digested.
Chew the (one's) cud is to reflect or meditate.
See also
- Monogastric
A monogastric organism has a simple single-chambered stomach, whereas ruminants have a four-chambered complex stomach. Examples of monogastric animals include humans, pigs, dogs, and cats....
- Digestive Physiology of Herbivores - Colorado State University