Cecotrope

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Cecotropes (also caecotropes, cecotrophs, cecal pellets, soft feces , or night feces) are a nutrient filled package created in the gastointestinal (GI) tract, expelled and eaten by rabbits and guinea pigs (among other animals) to get more nutrition out of their food. The first time through the GI tract, small particles of fiber are moved into the cecum (at the small intestine/colon junction), where microbes ferment them. This creates useable nutrients which are stored and expelled in cecotropes. The cecotropes are eaten and the nutrients are absorbed in the small intestine.

Contents

Terminology

Cecotropes are not fecal material but rather nutrition, [1] so terms such as "soft feces" and "night feces" are technically incorrect. Similarly, though cecotropes are sometimes called "night feces," they are in fact produced throughout the day and night. [2] [1] The act of eating cecotropes is known as cecotrophy (caecotrophy, cecophagy, pseudo-rumination, refection), [3] again as distinct from coprophagy (the eating of feces proper). [4] [5] Rabbits (and other animals discussed here) will occasionally engage in coprophagy. [5]

Cecotropes are a group of small balls clumped together that look like a thin blackberry, which exit the anus all at once. They are very dark (almost black) and smelly, look wet, are sticky (as they are covered in mucus), are very soft, and are full of nutrition. [3] [6]

Cecotropes differ from regular feces (dry feces, hard feces, or fecal pellets), which are larger, single balls, exit the anus one at a time, are dark brown/dark gray, smell only slightly, have very little moisture, are harder and are a waste product. [3]

It is well known that lagomorphs (rabbits, hares, pikas) eat cecotropes. Some rodents do the same, including the beaver and probably all in the suborder Hystricomorpha (e.g., capybara, guinea pig, chinchilla). [7] [8]

Other animals also eat cecotropes, for example marsupials (common ringtail possum, coppery ringtail possum). [5] While the information in this article is specific to rabbits, much of the information also relates to all animals that eat cecotropes.

These animals are hindgut fermenters. [9] This means fibrous food material is fermented after the small intestine (in the cecum and/or colon). Small animals (discussed in this article) are classified as cecal fermenters while large animals are colonic fermenters. [10] They all have one stomach (monogastric). [10] Not all hindgut fermentators have ceca that make material for cecotropes that are reingested.

Overview

The stomach and small intestine digest food material. The small intestine also absorbs some digested material. The rest of the material then moves into the colon. Here material is separated according to size. The large particles continue to move down the colon while the small particles move back up the colon and into the cecum. The large particles are formed into regular feces and expelled. Meanwhile, the material in the cecum is fermented by microbes, producing nutrients that can later be absorbed. The material is then passed down the colon, formed into cecotropes, expelled and eaten. When the cecotropes move into the small intestine, the nutrients are absorbed.

Before the cecum

Animals discussed in this article are herbivores. [11] [12] Adults eat more than 30 meals a day. [13] The incisors cut the food (e.g., grass and forbs) while the premolars and molars grind it into smaller pieces. The organized tongue movements help to thoroughly chew the food. [14] Saliva (containing the enzyme amylase) starts the digestion process. [3] [13] The food material is swallowed down the esophagus and then reaches the stomach, where digestion continues. The stomach is 15% of the total volume of the GI tract [3] and has a pH of 1-2 (which is very acidic). [2]

Rabbits cannot vomit. This is because where the esophagus meets the stomach, rabbits have a massive muscular sphincter (with both smooth and striated muscles) along with a mucosal membrane flap that produces a watertight one-way seal. [15] They also lack the nerves necessary to vomit. [16]

Moving down to the small intestine (12% of GI tract), [3] digestion continues. Most absorption occurs in the small intestine, where the nutrients move through the walls and into the bloodstream. [7] Some absorption also occurs in the stomach, cecum and colon. [2]

The material then reaches the proximal (upper) colon. Between the proximal and distal (lower) colon is a small segment called the fusus coli, which is unique to lagomorphs. It regulates the separation of the material. [3] Particles greater than 0.3-0.5 mm (mainly non-fermentable material) move to the center of the colon and then peristalsis moves them down the colon. Particles less than 0.3-0.5 mm (mainly fermentable fiber and proteins) move to the sides, and then retrograde peristalsis moves them back up the colon and into the cecum. [14] [2] [17] [9]

The ileocecal valve (at the end of the small intestine) ensures the material goes to the cecum and not the small intestine. [2]

At the cecum

A rabbit's cecum is proportionally the largest of any mammal. It is 40% of the total volume of the GI tract. [3] The cecum is a blind sac coming off the small intestine/colon junction. At the end of the cecum is the vermiform appendix. [3]

Mammalian enzymes cannot break down fiber. [18] However, microbes in the cecum have enzymes that are capable of breaking down fiber. [13] The microbes include bacteria (mainly Bacteroides and also Bifidobacterium, Clostridium, Streptococcus, Enterobacter, Endophorus, Acuformis, Peptococcus, Peptostreptococcus, Fusobacterium, Coliform (usually in small numbers, e.g., Escherischia coli) and others), protozoa (ciliated and flagellated), an amoeboid organism (Entamoeba cuniculi) and a rabbit-specific yeast (Cyniclomyces guttulatulus). [3] [14] [2] [17] [19]

It is estimated that more than 50% of the microbes are not known. [17] Note that no Lactobacillus species are found in the microbiome of the rabbit and thus using L. acidophilus as a probiotic has unknown value. [2]

The anaerobic fermentation in the cecum breaks down the fiber into useable food for the animal. It is also used as food for the proliferating microbes. The results of the fermentation are volatile fatty acids (VFAs) (mostly acetic, butyric and propionic acids), all of the B vitamins, vitamin K, microbial proteins, essential amino acids and minerals. [20] [21] [3] [14] [2] [17] [9]

The cecum has a pH of 5.4-6.8, which does not harm the microbes. [17] Most of the VFAs are absorbed through the walls of the cecum. [2] [22]

Some of the other nutrients are also absorbed by the cecum and the colon. [3] Four to nine hours after a meal, the cecum empties and the contents (containing the results of fermentation, along with microbes) continue down the colon. [2] [13]

After the cecum

Microbes also live in the colon. [3] Cecotropes and regular feces pass through the colon at different times. Regular feces are formed in the fusus coli, continue through the colon and rectum and are expelled through the anus, about 4 hours after eating. [13] [2] They contain mainly insoluble fiber which is used for motility, not for nutrition. [3]

The material from the cecum is formed into cecotropes in the fusus coli, where it contracts more gently than when forming regular feces. [2] Goblet cells in the fusus coli secrete mucus which covers the cecotropes, which will protect them when they get into the acidic stomach. [3] [23] [2] An enzyme (lysozyme) is also added that aids digestion of microbial proteins. [2] [24] Cecotropes (pH about 7) continue through the colon and rectum and are expelled thru the anus, about eight hours after eating. [13]

Reingestion

Cecotropes are eaten directly from the anus. [21] They usually do not touch the ground. They are not chewed (even though it looks like it). [3] They are swallowed whole so the mucus is not disturbed. They are held in the fundic region of the stomach (at the top) for 3 to 6 hours where they continue to ferment. [3] [25]

Then they move into the small intestine [3] where the nutrients are absorbed, [7] about 17 hours after the original meal. [17]

The gastrointestinal tract of newborn rabbits is sterile and contains no microbes. The babies eat cecotropes and regular feces from the mother in order to obtain microbes that are needed for the cecum. Young rabbits start eating their own cecotropes at about day 20. [3]

The stomach of the babies has a pH of 5 to 6.5, which does not kill the microbes. However, when the mother's milk combines with an enzyme in the baby's stomach, it produces an antimicrobial fatty acid (octanoic and decanoic acids) (milk oil) which kills microbes. [2] Only after the milk oil decreases and before the stomach pH gets too low (as the baby ages) can the microbes survive the stomach conditions and pass into the cecum to proliferate. [3]

Why cecotrophy

Many herbivores have a diet that is low in nutrition and high in fiber (which is a non-starch polysaccharide carbohydrate). [13] Fiber can be either soluble (pectins and gums) or insoluble (cellulose, hemicellulose and lignocellulose). [13] A simple gastrointestinal tract is not capable of extracting enough nutrients for these animals.

One strategy to get the needed nutrition is used by ruminants (e.g., cows). They chew the cud in order to process their food a second time to extract more nutrients. [26] [20] Another strategy (e.g., used by horses) is to have a very long colon to aid in digestion and absorption. [17] Both of these strategies add substantial bulk to the animal.

Since the rabbit is at the bottom of the food chain, it must be nimble in order to out run its many predators. Creating cecotropes is a way to get more nutrients out of their food without adding a lot of bulk to their GI tract (which is 10% - 20% of their body weight). [3] Since their colons do not absorb the nutrients in the cecotropes, they reingest them so they can be absorbed in the small intestine. [27]

Disorder

It is essential to maintain a balanced microbiome in the gastrointestinal tract, especially the cecum. If beneficial microbes decrease and harmful microbes proliferate, the microbiome becomes unbalanced (called dysbiosis). [13] [1] [28] The cause of this includes a diet too high in carbohydrates and/or too low in indigestible fiber (which slows down gut motility and changes the pH of the cecum, among other things); toxins; some medications (especially some antibiotics); dehydration; extreme stress; dental disease and other systemic diseases (e.g., liver or kidney disease). If the balance is not maintained, there can be multiple health issues, including GI stasis, which can lead to pain, stress and death. [29] [6]

A few cecotropes left on the ground of the living area of the animal is not cause for concern. However, if a large amount is found on the ground or stuck to the fur, a veterinarian should be consulted. Possible causes are poor diet, dental issues, arthritis, very large dewlap, obesity, or too-long fur in the anal region. [13]

If the cecotropes are like pudding, it is called intermittent soft cecotropes (ISC). This is different from true diarrhea, which has no form, is completely watery and is very serious. If regular feces are also produced, it is not diarrhea. [13] [30]

ISC will stick to the hindquarters and feet of the animal and to places in the living area. Causes are a poor diet (too many carbohydrates, too little fiber) or inappropriate antibiotics. Treatment is to feed unlimited grass hay, greens and limited pellets and to stop giving inappropriate antibiotics. [30]

Related Research Articles

<span class="mw-page-title-main">Coprophagia</span> Consumption of feces

Coprophagia or coprophagy is the consumption of feces. The word is derived from the Ancient Greek κόπρος kópros "feces" and φαγεῖν phageîn "to eat". Coprophagy refers to many kinds of feces-eating, including eating feces of other species (heterospecifics), of other individuals (allocoprophagy), or one's own (autocoprophagy) – those once deposited or taken directly from the anus.

<span class="mw-page-title-main">Large intestine</span> Last part of the digestive system in vertebrates

The large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the digestive system in tetrapods. Water is absorbed here and the remaining waste material is stored in the rectum as feces before being removed by defecation. The colon is the longest portion of the large intestine, and the terms are often used interchangeably but most sources define the large intestine as the combination of the cecum, colon, rectum, and anal canal. Some other sources exclude the anal canal.

<span class="mw-page-title-main">Dietary fiber</span> Portion of plant-derived food that cannot be completely digested

Dietary fiber or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes. Dietary fibers are diverse in chemical composition, and can be grouped generally by their solubility, viscosity, and fermentability, which affect how fibers are processed in the body. Dietary fiber has two main components: soluble fiber and insoluble fiber, which are components of plant-based foods, such as legumes, whole grains and cereals, vegetables, fruits, and nuts or seeds. A diet high in regular fiber consumption is generally associated with supporting health and lowering the risk of several diseases. Dietary fiber consists of non-starch polysaccharides and other plant components such as cellulose, resistant starch, resistant dextrins, inulin, lignins, chitins, pectins, beta-glucans, and oligosaccharides.

<span class="mw-page-title-main">Gastrointestinal tract</span> Organ system within humans and other animals

The gastrointestinal tract is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and other animals, including the esophagus, stomach, and intestines. Food taken in through the mouth is digested to extract nutrients and absorb energy, and the waste expelled at the anus as faeces. Gastrointestinal is an adjective meaning of or pertaining to the stomach and intestines.

<span class="mw-page-title-main">Cecum</span> Pouch in the large intestine

The cecum or caecum is a pouch within the peritoneum that is considered to be the beginning of the large intestine. It is typically located on the right side of the body. The word cecum stems from the Latin caecus meaning blind.

<span class="mw-page-title-main">Small intestine</span> Organ in the gastrointestinal tract

The small intestine or small bowel is an organ in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the pancreatic duct to aid in digestion. The small intestine is about 5.5 metres long and folds many times to fit in the abdomen. Although it is longer than the large intestine, it is called the small intestine because it is narrower in diameter.

Digestion is the breakdown of large insoluble food compounds into small water-soluble components so that they can be absorbed into the blood plasma. In certain organisms, these smaller substances are absorbed through the small intestine into the blood stream. Digestion is a form of catabolism that is often divided into two processes based on how food is broken down: mechanical and chemical digestion. The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes. Mechanical digestion takes place in the mouth through mastication and in the small intestine through segmentation contractions. In chemical digestion, enzymes break down food into the small compounds that the body can use.

<span class="mw-page-title-main">Leporidae</span> Family of lagomorphs

Leporidae is the family of rabbits and hares, containing over 70 species of extant mammals in all. The Latin word Leporidae means "those that resemble lepus" (hare). Together with the pikas, the Leporidae constitute the mammalian order Lagomorpha. Leporidae differ from pikas in that they have short, furry tails and elongated ears and hind legs.

<span class="mw-page-title-main">Ruminant</span> Hoofed herbivorous grazing or browsing mammals

Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The process, which takes place in the front part of the digestive system and therefore is called foregut fermentation, typically requires the fermented ingesta to be regurgitated and chewed again. The process of rechewing the cud to further break down plant matter and stimulate digestion is called rumination. The word "ruminant" comes from the Latin ruminare, which means "to chew over again".

Colic in horses is defined as abdominal pain, but it is a clinical symptom rather than a diagnosis. The term colic can encompass all forms of gastrointestinal conditions which cause pain as well as other causes of abdominal pain not involving the gastrointestinal tract. What makes it tricky is that different causes can manifest with similar signs of distress in the animal. Recognizing and understanding these signs is pivotal, as timely action can spell the difference between a brief moment of discomfort and a life-threatening situation. The most common forms of colic are gastrointestinal in nature and are most often related to colonic disturbance. There are a variety of different causes of colic, some of which can prove fatal without surgical intervention. Colic surgery is usually an expensive procedure as it is major abdominal surgery, often with intensive aftercare. Among domesticated horses, colic is the leading cause of premature death. The incidence of colic in the general horse population has been estimated between 4 and 10 percent over the course of the average lifespan. Clinical signs of colic generally require treatment by a veterinarian. The conditions that cause colic can become life-threatening in a short period of time.

Abdominal bloating is a short-term disease that affects the gastrointestinal tract. Bloating is generally characterized by an excess buildup of gas, air or fluids in the stomach. A person may have feelings of tightness, pressure or fullness in the stomach; it may or may not be accompanied by a visibly distended abdomen. Bloating can affect anyone of any age range and is usually self-diagnosed, in most cases does not require serious medical attention or treatment. Although this term is usually used interchangeably with abdominal distension, these symptoms probably have different pathophysiological processes, which are not fully understood.

Extracellular phototropic digestion is a process in which saprobionts feed by secreting enzymes through the cell membrane onto the food. The enzymes catalyze the digestion of the food ie diffusion, transport, osmotrophy or phagocytosis. Since digestion occurs outside the cell, it is said to be extracellular. It takes place either in the lumen of the digestive system, in a gastric cavity or other digestive organ, or completely outside the body. During extracellular digestion, food is broken down outside the cell either mechanically or with acid by special molecules called enzymes. Then the newly broken down nutrients can be absorbed by the cells nearby. Humans use extracellular digestion when they eat. Their teeth grind the food up, enzymes and acid in the stomach liquefy it, and additional enzymes in the small intestine break the food down into parts their cells can use. Extracellular digestion is a form of digestion found in all saprobiontic annelids, crustaceans, arthropods, lichens and chordates, including vertebrates.

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<span class="mw-page-title-main">Equine nutrition</span> Feeding of domesticated equines such as horses, ponies, mules, and donkeys.

Equine nutrition is the feeding of horses, ponies, mules, donkeys, and other equines. Correct and balanced nutrition is a critical component of proper horse care.

Hindgut fermentation is a digestive process seen in monogastric herbivores. Cellulose is digested with the aid of symbiotic bacteria. The microbial fermentation occurs in the digestive organs that follow the small intestine: the large intestine and cecum. Examples of hindgut fermenters include proboscideans and large odd-toed ungulates such as horses and rhinos, as well as small animals such as rodents, rabbits and koalas. In contrast, foregut fermentation is the form of cellulose digestion seen in ruminants such as cattle which have a four-chambered stomach, as well as in sloths, macropodids, some monkeys, and one bird, the hoatzin.

Isomaltooligosaccharide (IMO) is a mixture of short-chain carbohydrates which has a digestion-resistant property. IMO is found naturally in some foods, as well as being manufactured commercially. The raw material used for manufacturing IMO is starch, which is enzymatically converted into a mixture of isomaltooligosaccharides.

<span class="mw-page-title-main">Human digestive system</span> Digestive system in humans

The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion. Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body. The process of digestion has three stages: the cephalic phase, the gastric phase, and the intestinal phase.

<span class="mw-page-title-main">Jarman–Bell principle</span> Ecological concept linking an herbivores diet and size

The Jarman–Bell principle is a concept in ecology that the food quality of a herbivore's intake decreases as the size of the herbivore increases, but the amount of such food increases to counteract the low quality foods. It operates by observing the allometric properties of herbivores. The principle was coined by P.J Jarman (1968.) and R.H.V Bell (1971).

<span class="mw-page-title-main">Grazing (behaviour)</span> Method of feeding in herbivores, eating grasses and other plants

Grazing is a method of feeding in which a herbivore feeds on low-growing plants such as grasses or other multicellular organisms, such as algae. Many species of animals can be said to be grazers, from large animals such as hippopotamuses to small aquatic snails. Grazing behaviour is a type of feeding strategy within the ecology of a species. Specific grazing strategies include graminivory ; coprophagy ; pseudoruminant ; and grazing on plants other than grass, such as on marine algae.

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