Hindgut fermentation
Encyclopedia
Hindgut fermentation is a digestive process seen in monogastric
herbivore
s, 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 intestine
and cecum
. Examples of hindgut fermenters include large odd-toed ungulate
s such as horses and rhino
s, as well as small animals such as rodent
s and rabbits. In contrast, foregut fermentation
is the form of cellulose digestion seen in ruminant
s such as cattle
which have a four-chambered stomach which digests cellulose.
Smaller hindgut fermenters of the order
Lagomorpha
(rabbits and pika
s) absorb the needed levels of nutrients via their upper digestive system by reingestion of cecotropes, which are passed through the intestines and subsequently reingested for added nutrients. Coprophagy is also practiced by some rodents, such as the capybara
, guinea pig
and related species.
While foregut fermentation is generally considered more efficient, and monogastric animals cannot digest cellulose as efficiently as ruminants, hindgut fermentation allows animals to consume small amounts of low-quality forage all day long and thus survive in conditions where ruminants might not be able to obtain nutrition adequate for their needs. Hindgut fermentors are able to extract more nutrition out of small quantities of feed. The large hind-gut fermenters are bulk feeders: they ingest large quantities of low-nutrient food, which they process for a longer time in a much longer intestine. The main food in that category is grass, and grassland grazers move over long distances to take advantage of the growth phases of grass in different regions.
Hindgut fermenters are subdivided into two groups based on the relative size of various digestive organs in relationship to the rest of the system: colon
ic fermenters tend to be larger species such as horses, and cecal fermenters are smaller animals such as rabbits and rodents. However, in spite of the terminology, colonic fermentors such as horses make extensive use of the cecum to break down cellulose.
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...
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, animals with a simple, single-chambered 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...
. 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....
is digested with the aid of symbiotic
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
bacteria. The microbial fermentation
Fermentation (biochemistry)
Fermentation is the process of extracting energy from the oxidation of organic compounds, such as carbohydrates, using an endogenous electron acceptor, which is usually an organic compound. In contrast, respiration is where electrons are donated to an exogenous electron acceptor, such as oxygen,...
occurs in the digestive organs that follow 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...
, namely 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 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...
. Examples of hindgut fermenters include large odd-toed ungulate
Odd-toed ungulate
An odd-toed ungulate is a mammal with hooves that feature an odd number of toes. Odd-toed ungulates comprise the order Perissodactyla . The middle toe on each hoof is usually larger than its neighbours...
s such as horses and rhino
Rhino
Rhino is a colloquial abbreviation of rhinoceros"Rhino" may also refer to:-Entertainment:* Rhino , a character from the Marvel Comics universe and sometime-foe of Spider-Man...
s, as well as small animals such as rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
s and rabbits. In contrast, foregut fermentation
Foregut fermentation
Foregut fermentation is a form of digestion that occurs in the foregut of some animals. It has evolved independently in several groups of mammals, and also in the hoatzin bird. All ruminants use foregut fermentation, whereas only some rodents and marsupials do. It has also evolved in colobine...
is the form of cellulose digestion seen in ruminant
Ruminant
A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...
s such as 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...
which have a four-chambered stomach which digests cellulose.
Smaller hindgut fermenters of the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Lagomorpha
Lagomorpha
The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two living families, the Leporidae , and the Ochotonidae...
(rabbits and pika
Pika
The pika is a small mammal, with short limbs, rounded ears, and short tail. The name pika is used for any member of the Ochotonidae, a family within the order of lagomorphs, which also includes the Leporidae . One genus, Ochotona, is recognised within the family, and it includes 30 species...
s) absorb the needed levels of nutrients via their upper digestive system by reingestion of cecotropes, which are passed through the intestines and subsequently reingested for added nutrients. Coprophagy is also practiced by some rodents, such as the capybara
Capybara
The capybara , also known as capivara in Portuguese, and capibara, chigüire in Venezuela, Colombia, and Ecuador ronsoco in Peru, chigüiro, and carpincho in Spanish, is the largest living rodent in the world. Its closest relatives are agouti, chinchillas, coyphillas, and guinea pigs...
, guinea pig
Guinea pig
The guinea pig , also called the cavy, is a species of rodent belonging to the family Caviidae and the genus Cavia. Despite their common name, these animals are not in the pig family, nor are they from Guinea...
and related species.
While foregut fermentation is generally considered more efficient, and monogastric animals cannot digest cellulose as efficiently as ruminants, hindgut fermentation allows animals to consume small amounts of low-quality forage all day long and thus survive in conditions where ruminants might not be able to obtain nutrition adequate for their needs. Hindgut fermentors are able to extract more nutrition out of small quantities of feed. The large hind-gut fermenters are bulk feeders: they ingest large quantities of low-nutrient food, which they process for a longer time in a much longer intestine. The main food in that category is grass, and grassland grazers move over long distances to take advantage of the growth phases of grass in different regions.
Hindgut fermenters are subdivided into two groups based on the relative size of various digestive organs in relationship to the rest of the system: colon
Colón
Colón is a Spanish and Portuguese surname, comparable to the Italian and Portuguese Colombo . It may refer to:People:* Cristóbal Colón, the Spanish language name for the explorer Christopher Columbus...
ic fermenters tend to be larger species such as horses, and cecal fermenters are smaller animals such as rabbits and rodents. However, in spite of the terminology, colonic fermentors such as horses make extensive use of the cecum to break down cellulose.