Difference between revisions of "Ruminant" - New World Encyclopedia

From New World Encyclopedia
 
(23 intermediate revisions by 3 users not shown)
Line 1: Line 1:
{{Images OK}}
+
{{Images OK}}{{Approved}}{{Copyedited}}
 
{{Taxobox
 
{{Taxobox
| image = Abomasum (PSF).png
+
| image = White-tailed deer.jpg
| image_width = 250px
+
| image_width = 240px
| image_caption = Rough illustration of a ruminant digestive system
+
| image_caption = White-tailed deer
 
| name = Ruminants
 
| name = Ruminants
 
| regnum = [[Animal]]ia
 
| regnum = [[Animal]]ia
Line 19: Line 19:
 
[[Tragulidae]]<br/>
 
[[Tragulidae]]<br/>
 
}}
 
}}
A '''ruminant''' is any even-toed, hooved [[mammal]] (order [[Ungulate#Artiodactyla: Even-toed ungulates|Artiodactyla]]) that digests its food in two steps, first by softening it within the animal's first stomach, known as the [[rumen]], then regurgitating the semi-digested mass, now known as [[cud]], and chewing it again. Most ungulates have a four-chambered stomach ([[Camelidae|camelids]] have three chambers), lack upper incisors (camelids have an upper incisor), and have two-toed feet (chevrotains have four toes). Among ruminating mammals are [[cattle]], [[goat]]s, [[sheep]], [[giraffe]]s, [[American Bison]], [[Wisent|European bison]], [[yak]]s, [[Bubalus|water buffalo]], [[deer]], [[camel]]s, [[alpaca]]s, [[llama]]s, [[wildebeest]], [[antelope]], [[pronghorn]], and [[nilgai]].
+
A '''ruminant''' is any even-toed, hooved [[mammal]] (order [[Ungulate#Artiodactyla: Even-toed ungulates|Artiodactyla]]) that digests its food in two steps, first by softening it within the animal's first [[stomach]], known as the [[rumen]], then regurgitating the semi-digested mass, now known as [[cud]], and chewing it again. Most ungulates have a four-chambered stomach ([[Camelidae|camelids]] have three chambers), lack upper incisors (camelids have an upper incisor), and have two-toed feet (chevrotains have four toes). Among ruminating mammals are [[cattle]], [[goat]]s, [[sheep]], [[giraffe]]s, [[American Bison]], [[Wisent|European bison]], [[yak]]s, [[Bubalus|water buffalo]], [[deer]], [[camel]]s, [[alpaca]]s, [[llama]]s, [[wildebeest]], [[antelope]], [[pronghorn]], and [[nilgai]].
  
 
Taxonomically, the suborder [[Ruminantia]] includes all those species except the camelids (camels, llamas, alpacas, etc.), which are in [[Tylopoda]]. Therefore, the term "ruminant" is not synonymous with Ruminantia. The process of again chewing the cud to further break down plant matter and stimulate digestion is called "ruminating."   
 
Taxonomically, the suborder [[Ruminantia]] includes all those species except the camelids (camels, llamas, alpacas, etc.), which are in [[Tylopoda]]. Therefore, the term "ruminant" is not synonymous with Ruminantia. The process of again chewing the cud to further break down plant matter and stimulate digestion is called "ruminating."   
  
Rumination involves a symbiotic relationship between ruminants and many [[microorganism|microbes]] in their digestive tract. Through producing [[cellulase]]s, he microbes are able to digest dietary [[cellulose]], the primary structural component of green plants, and other plant wall materials. In the process, the ruminants are able to obtain some of the end products of this [[fermentation]] for their own use, such as various [[fatty acid]]s. The microbes receive a habitat and a food source, while the ruminant benefits from being able to digest the most abundant organic (carbon-containing) compound on Earth (cellulose).
+
Rumination involves a symbiotic relationship between ruminants and many [[microorganism|microbes]] in their [[digestive tract]]. Through producing [[cellulase]]s, the microbes are able to digest dietary [[cellulose]], the primary structural component of green plants, and other plant wall materials. In the process, the ruminants are able to obtain some of the end products of this [[fermentation]] for their own use, such as various [[fatty acid]]s. The microbes receive a habitat and a food source, while the ruminant benefits from being able to digest the most abundant organic (carbon-containing) compound on Earth (cellulose).
 +
{{toc}}
 +
The verb ''to ruminate'' also has been extended [[metaphor]]ically to mean ''to thoughtfully ponder'' or ''to [[meditation|meditate]]'' on some topic. Similarly, ideas may be ''chewed on'' or ''digested.'' ''Chew the (one's) cud'' is to reflect or meditate.
  
The verb ''to ruminate'' also has been extended [[metaphor]]ically to mean ''to thoughtfully ponder'' or ''to [[meditation|meditate]]'' on some topic. Similarly, ideas may be ''chewed on'' or ''digested''. ''Chew the (one's) cud'' is to reflect or meditate.
+
==Overview==
 
 
==Overview and description==
 
 
Ruminants belong to the order [[Ungulate#Artiodactyla: Even-toed ungulates|Artiodactyla]]. Known as even-toed [[ungulate]]s, the axis of the leg passes between the third and fourth toes. The weight of most even-toed ungulates is born evenly on the third and fourth toe of each foot with the other toes being absent, or vestigial in the case of most [[deer]]. Except for [[hippopotamus]]es, [[peccary|peccaries]], and [[pig]]s, all even-toed ungulates digest their food by the process of rumination.
 
Ruminants belong to the order [[Ungulate#Artiodactyla: Even-toed ungulates|Artiodactyla]]. Known as even-toed [[ungulate]]s, the axis of the leg passes between the third and fourth toes. The weight of most even-toed ungulates is born evenly on the third and fourth toe of each foot with the other toes being absent, or vestigial in the case of most [[deer]]. Except for [[hippopotamus]]es, [[peccary|peccaries]], and [[pig]]s, all even-toed ungulates digest their food by the process of rumination.
  
Most ruminants belong to the suborder '''Ruminantia'''. Extant members of this suborder include the families Tragulidae (chevrotains), Moschidae (musk deer), Cervidae (deer), Giraffidae (giraffe and okapi), Antilocapridae (pronghorn), and Bovidae (cattle, goats, sheep, and antelope). Members of the Ruminantia suborder have a fore-stomach with four chambers. The nine extant species of chevrotain, also known as mouse deer and comprising the family Tragulidae, have four chambers, but the third is poorly developed. Chevrotains also have other features that are closer to non-ruminants such as pigs. They do not have [[horn (anatomy)|horns]] or [[antler]]s, and like the pigs, they have four toes on each foot.  
+
Most ruminants belong to the suborder '''Ruminantia'''. Extant members of this suborder include the families Tragulidae (chevrotains), Moschidae (musk deer), Cervidae (deer), Giraffidae (giraffe and okapi), Antilocapridae (pronghorn), and Bovidae (cattle, goats, sheep, and antelope). Members of the Ruminantia suborder have a fore-stomach with four chambers. The nine extant species of chevrotain, also known as mouse deer and comprising the family Tragulidae, have four chambers, but the third is poorly developed. Chevrotains also have other features that are closer to non-ruminants such as [[pig]]s. They do not have [[horn (anatomy)|horns]] or [[antler]]s, and like the pigs, they have four toes on each foot.  
  
The remaining ruminants belong to the suborder '''Tylopoda'''. Meaning "padded foot," this suborder contains the camel family, Camelidae. Included in Camelidae are [[camel]]s and the South American [[llama]]s, [[alpaca]]s, [[guanaco]]s, and [[vicuña]]s. Although considered ruminants&mdash;any [[ungulate]] of the order Artiodactyla that chews its cud&mdash;camelids differ from those members of Ruminantia in several ways. They have a three-chambered rather than a four-chambered digestive tract; an upper lip that is split in two with each part separately mobile; an isolated incisor in the upper jaw; and, uniquely among mammals, elliptical red blood cells and a special type of antibodies lacking the light chain, besides the normal antibodies found in other species.
+
The remaining ruminants belong to the suborder '''Tylopoda'''. Meaning "padded foot," this suborder contains the camel family, Camelidae. Included in Camelidae are [[camel]]s (''Camelus dromedarius'' and ''Camelus bactrianus''), and the South American [[llama]]s ''(Lama glama),'' [[alpaca]]s (''Lama pacos'' or ''Vicugna pacos''), [[guanaco]]s ''(Lama guanicoe),'' and [[vicuña]]s ''(Vicugna vicugna)''. Although considered ruminants&mdash;any [[ungulate]] of the order Artiodactyla that chews its cud&mdash;camelids differ from those members of Ruminantia in several ways. They have a three-chambered rather than a four-chambered digestive tract; an upper lip that is split in two with each part separately mobile; an isolated incisor in the upper jaw; and, uniquely among mammals, elliptical red blood cells and a special type of antibodies lacking the light chain, besides the normal antibodies found in other species.
  
 
==Structure and process of digestion==
 
==Structure and process of digestion==
 
+
[[Image:Abomasum (PSF).png|thumb|right|300px|Rough illustration of a ruminant digestive system]]
 
The basic four chambers of the stomach in members of Ruminantia are the [[rumen]], [[Reticulum (anatomy)|reticulum]], [[omasum]], and [[abomasum]]. Together, these compartments occupy about three-quarters of the abdominal cavity, filling almost all of the left side and extensive portions of the right (Bowen 2003).
 
The basic four chambers of the stomach in members of Ruminantia are the [[rumen]], [[Reticulum (anatomy)|reticulum]], [[omasum]], and [[abomasum]]. Together, these compartments occupy about three-quarters of the abdominal cavity, filling almost all of the left side and extensive portions of the right (Bowen 2003).
  
The first two chambers, the '''rumen''' and the '''reticulum''', while having different names, represent the same functional space as digesta, or ingesta, can move back and forth between them. Together, these chambers are called the reticulorumen. In some respects, the reticulum can be viewed as a "cranioventral sac of the rumen" (Bowen 2003). The reticulum lies next the diaphragm and is connected to the rumen by a fold of tissue. The rumen is by far the largest of the fore-stomachs; it itself is divided by muscular pillars into the dorsal, ventral, caudodorsal, and caudoventral sacs (Bowen 2003).  
+
The first two chambers or the ruminant stomach, the '''rumen''' and the '''reticulum''', while having different names, represent the same functional space, as digesta (or ingesta) can move back and forth between them. Together, these chambers are called the reticulorumen. In some respects, the reticulum can be viewed as a "cranioventral sac of the rumen" (Bowen 2003). The reticulum lies next the diaphragm and is connected to the rumen by a fold of tissue. The rumen is by far the largest of the fore-stomachs; it itself is divided by muscular pillars into the dorsal, ventral, caudodorsal, and caudoventral sacs (Bowen 2003).  
  
In these 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]]). The cud is then regurgitated, chewed slowly to completely mix it with saliva and to break down the particle size. Fiber, especially [[cellulose]] and [[hemi-cellulose]], is primarily broken down into the three [[volatile fatty acids]], [[acetic acid]], [[propionic acid]], and [[butyric acid]] in these chambers by microbes ([[bacteria]], [[protozoa]], and [[fungi]]). Protein and non-structural carbohydrate ([[pectin]], [[sugars]], [[starches]]) are also fermented.
+
In these first two chambers, the food is mixed with [[saliva]] and separates into layers of solid and liquid material. Solids clump together to form the cud (or [[bolus]]). The cud is then regurgitated, chewed slowly to completely mix it with saliva and to break down the particle size. Fiber, especially [[cellulose]] and [[hemi-cellulose]], is primarily broken down into the three [[volatile fatty acids]], [[acetic acid]], [[propionic acid]], and [[butyric acid]] in these chambers by microbes ([[bacteria]], [[protozoa]], and [[fungi]]). Protein and non-structural carbohydrate ([[pectin]], [[sugars]], [[starches]]) are also fermented.
  
 
The degraded digesta, which is now in the lower liquid part of the reticulorumen, then passes into the next chamber, the '''omasum'''. The spherical omasum is connected to the reticulum by a short tunnel. It is in the omasum where water and many of the inorganic mineral elements are absorbed into the blood stream (Bowen 2003).  
 
The degraded digesta, which is now in the lower liquid part of the reticulorumen, then passes into the next chamber, the '''omasum'''. The spherical omasum is connected to the reticulum by a short tunnel. It is in the omasum where water and many of the inorganic mineral elements are absorbed into the blood stream (Bowen 2003).  
Line 46: Line 46:
 
After this, the digesta is moved to the last chamber, the '''abomasum'''. The abomasum is the direct equivalent of the monogastric stomach (for example that of the human or pig), to which it is very similar histologically (Bowen 2003), and digesta is digested here in much the same way.  
 
After this, the digesta is moved to the last chamber, the '''abomasum'''. The abomasum is the direct equivalent of the monogastric stomach (for example that of the human or pig), to which it is very similar histologically (Bowen 2003), 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 intestine in the same way as in the reticulorumen.
+
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 in the same way as in the reticulorumen.
  
The forestomach anatomy of camelids is different, in having an omasum that is tubular and almost indistinct, and having a reticulum with areas of gland-like cells. For such a reason, camelids are sometimes referred to as "pseudoruminants" or as having "three stomach" instead of four (Bowen 2003).
+
The fore-stomach anatomy of camelids is different, in having an omasum that is tubular and almost indistinct, and having a reticulum with areas of gland-like cells. For such a reason, camelids are sometimes referred to as having "three stomachs" instead of four (Bowen 2003). While camelids regurgitate and rechew ingested forage as do all ruminants, their method of extracting protein and energy is more efficient. These differences have led some to claim that the camelids are not true ruminants (Fowler 2010).
  
The fermentation in the ruminant digestive system depends on [[bacteria]], [[protozoa[[, and [[fungi]]. Bowen (1998) notes that each milliliter of rumen content has roughly 10 to 50 billion bacteria, one million protozoa, and variable numbers of yeasts and fungi, almost all of which are anaeobes or faculative anaerobes, given that the environment of the rumen is anaeobic. There are a wide variety of bacteria, including those that are cellulolytic (digest cellulose), hemicellulolytic (digest hemicellulose), amylolytic (digest starch), and so forth. Protozoans, mainly ciliates, contribute substantially to fermentation, with experiments demonstrating that lambs and calves deprived of ruminal protozoa show poor growth rates, among other indicators of doing poorly (Bowen 1998).
+
The fermentation in the ruminant digestive system depends on [[bacteria]], [[protozoa]], and [[fungi]]. Bowen (1998) notes that each milliliter of rumen content has roughly 10 to 50 billion bacteria, one million protozoa, and variable numbers of [[yeast]]s and fungi, almost all of which are anaeobes or faculative anaerobes, given that the environment of the rumen is anaerobic. There are a wide variety of bacteria, including those that are cellulolytic (digest cellulose), hemicellulolytic (digest hemicellulose), amylolytic (digest [[starch]]), and so forth. Protozoans (mainly ciliates) contribute substantially to fermentation, with experiments demonstrating that lambs and calves deprived of ruminal protozoa show poor growth rates, among other indicators of doing poorly (Bowen 1998).
  
 
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 glucose from the [[small intestine]]. 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.
 
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 glucose from the [[small intestine]]. 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.
 +
 +
==Taxonomy==
 +
Extant ruminants comprise the following families within Artiodactyla:
 +
 +
* '''ORDER [[artiodactyla|Artiodactyla]]'''
 +
** '''Suborder Tylopoda'''
 +
*** Family [[Camelidae]]: [[camel]], [[llama]], [[alpaca]], [[vicuña]], and [[guanaco]], 6 living species in three genera
 +
** '''Suborder Ruminantia'''
 +
*** Family †[[Amphimerycidae]]
 +
*** Infraorder [[Tragulina]] (paraphyletic)
 +
**** Family [[Tragulidae]]: [[chevrotain]], 6 living species in 4 genera
 +
*** Infraorder [[Pecora]]
 +
**** Family [[Moschidae]]: [[musk deer]], 4 living species in one genus
 +
**** Family [[Cervidae]]: [[deer]], 49 living species in 16 genera
 +
**** Family [[Giraffidae]]: [[giraffe]] and [[okapi]], 2 living species in 2 genera
 +
**** Family [[Antilocapridae]]: [[pronghorn]], one living species in one genus
 +
**** Family [[Bovidae]]: [[cattle]], [[capra (genus)|goat]], [[sheep]], and [[antelope]], 135 living species in 48 genera
  
 
==Religious importance==
 
==Religious importance==
In [[Abrahamic]] religions, a distinction between clean and [[unclean animal]]s approximately falls according to whether the animal ruminates. The [[Law of Moses]] in the [[Bible]] allowed only the eating of animals that had split hooves and "that chew the cud" (''Leviticus'' 11:6), a stipulation preserved to this day in the [[Kashrut]].  
+
In [[Abrahamic religions]], a distinction between clean and [[unclean animal]]s approximately falls according to whether the animal ruminates. The [[Law of Moses]] in the [[Bible]] allowed only the eating of animals that had split hooves and "that chew the cud" (''Leviticus'' 11:6), a stipulation preserved to this day in the [[Kashrut]].  
  
 
Some believe that the [[Koran]] considers a mammal [[halal]] only if it is ruminant. However, this is not true. (Halal means an object or an action that is permissible to use or engage in, according to Islamic law and custom (opposed to haraam), and the term is widely used to designate food seen as permissible according to Islamic law.)
 
Some believe that the [[Koran]] considers a mammal [[halal]] only if it is ruminant. However, this is not true. (Halal means an object or an action that is permissible to use or engage in, according to Islamic law and custom (opposed to haraam), and the term is widely used to designate food seen as permissible according to Islamic law.)
  
 
==References==   
 
==References==   
* Bowen, R. 1998. [http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/herbivores/microbes.html Fermentation microbiology and ecology]. ''Colorado State University''. Retrieved December 24, 2008.
+
* Bowen, R. 1998. [http://www.vivo.colostate.edu/hbooks/pathphys/digestion/herbivores/microbes.html Fermentation microbiology and ecology]. ''Colorado State University''. Retrieved July 22, 2019.
   
+
* Bowen, R. 2003. [http://www.vivo.colostate.edu/hbooks/pathphys/digestion/herbivores/rumen_anat.html Digestive anatomy in ruminants]. ''Colorado State University''. Retrieved July 22, 2019.
* Bowen, R. 2003. [http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/herbivores/rumen_anat.html Digestive anatomy in ruminants]. ''Colorado State University''. Retrieved December 24, 2008.
+
* Bowen, R. 2006. [http://www.vivo.colostate.edu/hbooks/pathphys/digestion/herbivores/index.html Digestive physiology of herbivores]. ''Colorado State University''. Retrieved July 22, 2019.
 
+
* Fowler, M.F. 2010. ''Medicine and Surgery of Camelids''. Wiley-Blackwell. ISBN 9780813806167.
* Bowen, R. 2006. [http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/herbivores/index.html Digestive physiology of herbivores]. ''Colorado State University''. Retrieved December 24, 2008.
+
* Nowak, R. M., and J. L. Paradiso. 1983. ''Walker's Mammals of the World,'' 4th edition. Baltimore: Johns Hopkins University Press. ISBN 0801825253.
 
+
* Van Soest, P. J. 1994. ''Nutritional Ecology of the Ruminant.'' Ithaca: Comstock Pub. ISBN 080142772X.
* Nowak, R. M., and J. L. Paradiso. 1983. ''Walker's Mammals of the World'', 4th edition. Baltimore: Johns Hopkins University Press. ISBN 0801825253.
 
  
 
[[Category:Life sciences]]
 
[[Category:Life sciences]]
Line 72: Line 88:
 
[[Category:Ungulates]]
 
[[Category:Ungulates]]
  
{{credit|Ruminant|256515071|Chevrotain|258563742}}
+
{{credit|Ruminant|256515071|Chevrotain|258563742|Ruminantia|253404512}}

Latest revision as of 19:27, 3 August 2019

Ruminants
White-tailed deer
White-tailed deer
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Families

Antilocapridae
Bovidae
Camelidae
Cervidae
Giraffidae
Moschidae
Tragulidae

A ruminant is any even-toed, hooved mammal (order Artiodactyla) that digests its food in two steps, first by softening it within the animal's first stomach, known as the rumen, then regurgitating the semi-digested mass, now known as cud, and chewing it again. Most ungulates have a four-chambered stomach (camelids have three chambers), lack upper incisors (camelids have an upper incisor), and have two-toed feet (chevrotains have four toes). Among ruminating mammals are cattle, goats, sheep, giraffes, American Bison, European bison, yaks, water buffalo, deer, camels, alpacas, llamas, wildebeest, antelope, pronghorn, and nilgai.

Taxonomically, the suborder Ruminantia includes all those species except the camelids (camels, llamas, alpacas, etc.), which are in Tylopoda. Therefore, the term "ruminant" is not synonymous with Ruminantia. The process of again chewing the cud to further break down plant matter and stimulate digestion is called "ruminating."

Rumination involves a symbiotic relationship between ruminants and many microbes in their digestive tract. Through producing cellulases, the microbes are able to digest dietary cellulose, the primary structural component of green plants, and other plant wall materials. In the process, the ruminants are able to obtain some of the end products of this fermentation for their own use, such as various fatty acids. The microbes receive a habitat and a food source, while the ruminant benefits from being able to digest the most abundant organic (carbon-containing) compound on Earth (cellulose).

The verb to ruminate also has been extended metaphorically to mean to thoughtfully ponder or to meditate on some topic. Similarly, ideas may be chewed on or digested. Chew the (one's) cud is to reflect or meditate.

Overview

Ruminants belong to the order Artiodactyla. Known as even-toed ungulates, the axis of the leg passes between the third and fourth toes. The weight of most even-toed ungulates is born evenly on the third and fourth toe of each foot with the other toes being absent, or vestigial in the case of most deer. Except for hippopotamuses, peccaries, and pigs, all even-toed ungulates digest their food by the process of rumination.

Most ruminants belong to the suborder Ruminantia. Extant members of this suborder include the families Tragulidae (chevrotains), Moschidae (musk deer), Cervidae (deer), Giraffidae (giraffe and okapi), Antilocapridae (pronghorn), and Bovidae (cattle, goats, sheep, and antelope). Members of the Ruminantia suborder have a fore-stomach with four chambers. The nine extant species of chevrotain, also known as mouse deer and comprising the family Tragulidae, have four chambers, but the third is poorly developed. Chevrotains also have other features that are closer to non-ruminants such as pigs. They do not have horns or antlers, and like the pigs, they have four toes on each foot.

The remaining ruminants belong to the suborder Tylopoda. Meaning "padded foot," this suborder contains the camel family, Camelidae. Included in Camelidae are camels (Camelus dromedarius and Camelus bactrianus), and the South American llamas (Lama glama), alpacas (Lama pacos or Vicugna pacos), guanacos (Lama guanicoe), and vicuñas (Vicugna vicugna). Although considered ruminants—any ungulate of the order Artiodactyla that chews its cud—camelids differ from those members of Ruminantia in several ways. They have a three-chambered rather than a four-chambered digestive tract; an upper lip that is split in two with each part separately mobile; an isolated incisor in the upper jaw; and, uniquely among mammals, elliptical red blood cells and a special type of antibodies lacking the light chain, besides the normal antibodies found in other species.

Structure and process of digestion

Rough illustration of a ruminant digestive system

The basic four chambers of the stomach in members of Ruminantia are the rumen, reticulum, omasum, and abomasum. Together, these compartments occupy about three-quarters of the abdominal cavity, filling almost all of the left side and extensive portions of the right (Bowen 2003).

The first two chambers or the ruminant stomach, the rumen and the reticulum, while having different names, represent the same functional space, as digesta (or ingesta) can move back and forth between them. Together, these chambers are called the reticulorumen. In some respects, the reticulum can be viewed as a "cranioventral sac of the rumen" (Bowen 2003). The reticulum lies next the diaphragm and is connected to the rumen by a fold of tissue. The rumen is by far the largest of the fore-stomachs; it itself is divided by muscular pillars into the dorsal, ventral, caudodorsal, and caudoventral sacs (Bowen 2003).

In these first two chambers, the food is mixed with saliva and separates into layers of solid and liquid material. Solids clump together to form the cud (or bolus). The cud is then regurgitated, chewed slowly to completely mix it with saliva and to break down the particle size. Fiber, especially cellulose and hemi-cellulose, is primarily broken down into the three volatile fatty acids, acetic acid, propionic acid, and butyric acid in these chambers by microbes (bacteria, protozoa, and fungi). Protein and non-structural carbohydrate (pectin, sugars, starches) are also fermented.

The degraded digesta, which is now in the lower liquid part of the reticulorumen, then passes into the next chamber, the omasum. The spherical omasum is connected to the reticulum by a short tunnel. It is in the omasum where water and many of the inorganic mineral elements are absorbed into the blood stream (Bowen 2003).

After this, the digesta is moved to the last chamber, the abomasum. The abomasum is the direct equivalent of the monogastric stomach (for example that of the human or pig), to which it is very similar histologically (Bowen 2003), 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 in the same way as in the reticulorumen.

The fore-stomach anatomy of camelids is different, in having an omasum that is tubular and almost indistinct, and having a reticulum with areas of gland-like cells. For such a reason, camelids are sometimes referred to as having "three stomachs" instead of four (Bowen 2003). While camelids regurgitate and rechew ingested forage as do all ruminants, their method of extracting protein and energy is more efficient. These differences have led some to claim that the camelids are not true ruminants (Fowler 2010).

The fermentation in the ruminant digestive system depends on bacteria, protozoa, and fungi. Bowen (1998) notes that each milliliter of rumen content has roughly 10 to 50 billion bacteria, one million protozoa, and variable numbers of yeasts and fungi, almost all of which are anaeobes or faculative anaerobes, given that the environment of the rumen is anaerobic. There are a wide variety of bacteria, including those that are cellulolytic (digest cellulose), hemicellulolytic (digest hemicellulose), amylolytic (digest starch), and so forth. Protozoans (mainly ciliates) contribute substantially to fermentation, with experiments demonstrating that lambs and calves deprived of ruminal protozoa show poor growth rates, among other indicators of doing poorly (Bowen 1998).

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 glucose from the small intestine. 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.

Taxonomy

Extant ruminants comprise the following families within Artiodactyla:

  • ORDER Artiodactyla
    • Suborder Tylopoda
    • Suborder Ruminantia
      • Family †Amphimerycidae
      • Infraorder Tragulina (paraphyletic)
      • Infraorder Pecora
        • Family Moschidae: musk deer, 4 living species in one genus
        • Family Cervidae: deer, 49 living species in 16 genera
        • Family Giraffidae: giraffe and okapi, 2 living species in 2 genera
        • Family Antilocapridae: pronghorn, one living species in one genus
        • Family Bovidae: cattle, goat, sheep, and antelope, 135 living species in 48 genera

Religious importance

In Abrahamic religions, a distinction between clean and unclean animals approximately falls according to whether the animal ruminates. The Law of Moses in the Bible allowed only the eating of animals that had split hooves and "that chew the cud" (Leviticus 11:6), a stipulation preserved to this day in the Kashrut.

Some believe that the Koran considers a mammal halal only if it is ruminant. However, this is not true. (Halal means an object or an action that is permissible to use or engage in, according to Islamic law and custom (opposed to haraam), and the term is widely used to designate food seen as permissible according to Islamic law.)

References
ISBN links support NWE through referral fees

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

The history of this article since it was imported to New World Encyclopedia:

Note: Some restrictions may apply to use of individual images which are separately licensed.