The Reticulum is Continuous With Which Other Compartment of the Ruminant Stomach

Alimentary System and the Peritoneum, Omentum, Mesentery, and Peritoneal Cavity1

Howard B. Gelberg , in Pathologic Basis of Veterinary Disease (Sixth Edition), 2017

Rumen, Reticulum, and Omasum

The three compartments of the ruminant forestomach are the reticulum, rumen, and omasum. Folds and compartments subdivide the forestomach. Normal forestomach motility, and thus innervation, is critical in maintaining digestive homeostasis. The ruminant forestomachs are aglandular. The resident flora and fauna are responsible for digestion and fermentation of cellulose. In general, the rumen is a large fermentation vat where microorganisms break down ingesta by mechanical and chemical action into short-chain fatty acids that are directly absorbed across the epithelial lining into the blood. These fatty acids supply more than half of the energy from nutrients absorbed by the alimentary tract. The reticulum and omasum act mechanically to further reduce the ingesta to fine particles.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780323357753000072

Biology and Diseases of Ruminants: Sheep, Goats, and Cattle

Margaret L. Delano , ... Wendy J. Underwood , in Laboratory Animal Medicine (Second Edition), 2002

A. Unique Physiological Characteristics and Attributes, with Emphasis on Comparative Physiology

The development of the digestive system and the unique function of the rumen are among the most notable comparative anatomic and physiologic characteristics of ruminants. There is a three-compartment forestomach (rumen, reticulum, and omasum) and a true stomach (abomasum). The mature rumen functions as an anaerobic fermentation chamber in which the enzymes, such as cellulase, of the resident bacteria allow the animals to prosper as herbivores. Digestion is also aided by other microorganisms, such as protozoa (10 ⁵–10⁶/ml) and bacteria (10⁹–10¹⁰/ml), that contribute to rumen fermentation. The result is the production of volatile fatty acids (acetic, propionic, and butyric). Unlike in the monogastrics, fermentative digestion and volatile fatty acid absorption also occur in the large intestines. The main sources of energy for ruminants are volatile fatty acids (VFAs) rather than glucose. Glucose is formed from propionic acid (or from amino acids) for metabolism in the central nervous system (CNS), uterus, and mammary glands. Plasma glucose in ruminants is much lower than and is regulated differently from that in nonruminants. The rumen microorganisms also synthesize vitamins, such as B and K, and provide protein that is used by the animals' systems. Large amounts of fermentation gases such as CO₂ and methane, and small amounts of nitrogen, are naturally eructed (Hecker, 1983; Schimdt et al., 1988).

Intestinal immunoglobulin absorption by pinocytosis in the neonates is crucial to the success of passive transfer. This transfer mechanism is functional for approximately the first 36 hr after birth. Neonatal ruminants are immunocompetent, however, and this condition is used to advantage for vaccinations against some common diseases of the neonatal and later juvenile periods, such as infectious bovine rhinotracheitis (IBR) vaccine (using modified live virus vaccines) to calves when their dams' colostrum is lacking antibody against this virus.

Unlike hepatic lipogenesis in humans, lipogenesis in sheep primarily occurs in adipose tissue and the mammary gland (Hecker, 1983). In addition to normal lymph node chains, and as in other ruminants, sheep have small red "nodes" associated with blood vessels. Inadvertently named hemal "lymph nodes," they contain numerous red blood cells. Sheep have a relatively large pituitary gland, and accessory adrenal medullary tissue may be interspersed throughout the abdominal cavity.

Three major ovine histocompatability classes have been identified and designated as OVAR (Ovis aries) classes I, II, and III (Franz-Werner et al., 1996). Bovines are recognized as having several unique aspects involving their immune systems. The bovine lymphocyte antigen (BoLA) system ranks after the human (HLA) and murine (H-2) systems in terms of depth of knowledge (Lewin, 1996). Cattle are considered free of autoimmune diseases (Schook and Lamont, 1996).

The complexity of the immunobiology of the bovine mammary gland is being studied extensively because mastitis is the most prevalent disease in the dairy industry. Several innate immune mechanisms and cellular defenses, and their variation throughout lactation, have been described (Sordillo et al., 1997).

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B978012263951750017X

Biology and Diseases of Ruminants (Sheep, Goats, and Cattle)

Wendy J. Underwood DVM, MS, DACVIM , ... Adam Schoell DVM, DACLAM , in Laboratory Animal Medicine (Third Edition), 2015

A Unique Physiological Characteristics and Attributes, with Emphasis on Comparative Physiology

The development of the digestive system, including the unique function of the rumen, is among the most notable comparative anatomic and physiologic characteristic of ruminants. These species have a three-compartment forestomach (rumen, reticulum, and omasum) and a true stomach (abomasum). The mature rumen functions as an anaerobic fermentation chamber in which the enzymes, such as cellulase, of the resident bacteria (10 ⁹–10¹⁰/ml), allow the animal to prosper as an herbivore. Digestion is also aided by other microorganisms, such as protozoa (10⁵–10⁶/ml) and fungi, which contribute to the rumen ecosystem. The result is the production of volatile fatty acids (VFA: acetic, propionic, and butyric). Unlike the monogastrics, fermentative digestion and VFA absorption also occur in the large intestines. These VFA serve as the main sources of energy for ruminants rather than glucose. Glucose is formed from propionic acid (or from amino acids) for metabolism in the central nervous system, uterus, and mammary gland. Plasma glucose is much lower and regulated differently in ruminants than in nonruminants. Rumen microorganisms also synthesize B-complex vitamins and vitamin K, and provide protein utilized by the animals' systems. Large amounts of fermentation gases such as carbon dioxide and methane are naturally eructated (Jurgens et al., 2013; Reece 2004). Sheep and goats have tidy 'pelleted' dark-green feces. Cattle have pasty, moist, dark-green–brown feces.

Intestinal immunoglobulin absorption in neonates is crucial to the success of passive transfer. This transfer mechanism is functional for approximately the first 36   h after birth. Neonatal ruminants are immunocompetent, and this advantage is utilized when vaccinating calves against some common neonatal or juvenile diseases when the dams' colostrum is lacking antibody against those pathogens.

Three major ovine histocompatibility classes have been identified and are designated as OVAR (Ovis aries) Class I, II, and III (Franz-Werner et al., 1996; Gao et al., 2010). Bovines have several unique aspects of their immune systems. The bovine lymphocyte antigen system (BoLA) ranks after the human (HLA) and murine (H-2) systems in terms of depth of knowledge (Lewin, 1996). The complexity of the immunobiology of the bovine mammary gland is being studied extensively because mastitis is the most prevalent disease in the dairy industry. Several innate immune mechanisms and cellular defenses, and their variation throughout lactation, have been described (Sordillo and Streicher, 2002).

Bovine corneal epithelium is distinguished from other species because of its ability to heal without treatment, even when severely infected. Corneal ulcers are uncommon in sheep or goats.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780124095274000158

OFFAL | Types of Offal

W.F. Spooncer , in Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003

Tripe

Cattle and sheep stomachs have four compartments, all of which can be used to make tripe. Tripe from the rumen and reticulum is the most common. Rumen tripe is known as blanket tripe and reticulum tripe is known as the honeycomb. The internal surface of the rumen has densely packed papillae, while the reticulum has ridges in the shape of a honeycomb structure. In addition, there are thickened folds in the rumen wall. These folds contain a core of smooth muscle and are not covered by papillae. The fold can be trimmed out of the rumen to produce pillae tripe, known commercially as pillar or mountain chain.

The third compartment of the ruminant stomach is the omasum. The internal wall is in the form of deep, thin folds like the pages of a book. This appearance accounts for the popular name for the omasum, which is 'bible.' Although the omasum has a delicate flavor and texture, it is not commonly used as tripe because of the difficulty of cleaning the stomach contents from between the folds. The fourth part of the ruminant stomach is the abomasum, sometimes called the reed.

The four parts of the stomach are collected in one piece and the omental fat (caul fat) and spleen are removed. The neck of the omasum is cut to separate the rumen and reticulum from the omasum and abomasum. The rumen is cut open and the contents of the rumen and reticulum washed out. The rumen and reticulum are then trimmed into the different tripes, and external fat is trimmed off. Mountain chain tripe does not receive further processing, but blanket and honeycomb tripes may be further cleaned, scalded, and bleached with hydrogen peroxide.

The walls of ruminant stomachs are composed of smooth muscle and connective tissue. The papillae in the rumen are composed of collagen and elastin fibers covered with cornified epithelia, while the ridges and folds in the reticulum and omasum contain smooth muscle as well as connective tissue. There are small, cornified papillae on the folds of the omasum, and the surfaces of the folds are covered by a keratinized mucous membrane. The abomasum has a thick epithelial lining.

Tripes are generally tough because of the high connective tissue content. They contain about 35   g of collagen per 100   g of protein. They require prolonged, moist cooking to tenderize them. Bleached tripe is treated with caustic soda and has a pH of about 7–9, which increases the water-holding capacity and helps to tenderize the tripe.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B012227055X008579

Diseases of the gastrointestinal system

Jenna E. Bayne , Misty A. Edmondson , in Sheep, Goat, and Cervid Medicine (Third Edition), 2021

Ultrasonography

Ultrasonography is well suited for examination of the ruminant GIT and other abdominal viscera. Ultrasonography allows the characterization of contour, dimensions, content, and motility patterns of the forestomach and intestines, as well as the presence of masses, intraluminal and free abdominal fluid, and lesions within the parenchyma of abdominal viscera. Ultrasonography also can be used to guide fluid and tissue sampling for abdominocentesis and biopsy of organs or masses, respectively. ²⁰ Normal parameters for the forestomach compartments, small and large intestines, liver, and spleen have been described in small ruminants. ^{21 , 22} Imaging is best achieved using a linear or convex transducer with a frequency of 3.5 to 5.0 MHz. The reticulum is imaged in the cranioventral abdomen, bilaterally, as a crescent-shaped structure immediately adjacent to the diaphragm. Goats demonstrate monophasic, biphasic, and triphasic reticular contractions. ²³ The rumen is visualized in the 8th through 12th intercostal spaces (ICS) and flank on the left, and from the 12th ICS and flank on the right. The rumen wall appears as a thick echoic line, and the ability to differentiate the gas cap, fiber mat, and fluid layer is variable. Rumen motility is discerned indirectly by changes seen in layering of the ruminal content. The dorsal and ventral rumen sacs are most easily distinguished caudally by the presence of the longitudinal groove. ²⁴ The omasum is found on the right side from the 6th to 11th ICS (mainly in the 8th and 9th ICS), appears as a crescent-shaped echoic line medial to the liver, and moves passively with respiration due to its proximity to the diaphragm. Due to the gaseous nature of omasal content, the omasal leaves and omasal wall furthest from the transducer cannot be visualized. ²⁵ The abomasum is visualized along the ventral midline and to the left and right paramedian areas as a heterogeneous, moderately echoic structure with echogenic stippling. Visualization of abomasal folds as prominent echoic bands is possible in approximately two-thirds of goats. ²⁶ Examination of the small intestine takes place from the 8th to 12th ICS and the flank on the right side, from dorsal to ventral midline. Similarly, the large intestine (i.e., spiral colon and cecum) is visualized in the right flank. The descending duodenum can be differentiated based on proximity to abdominal wall and location between two serosal layers of greater omentum, whereas the jejunum and ileum cannot be differentiated from each other. Normal luminal diameters and wall thickness of the small intestine are described in normal goats. ²⁷ The spiral colon and cecum are visible in the caudal right flank. The spiral colon often located medial to the small intestine, is garland-like in appearance, and visualization of only the wall closest to the transducer is possible due to intraluminal gas, which is also true of the cecum. ²⁷ Ultrasonography of the liver for position, parenchymal and surface appearance, as well as visualization of the caudal vena cava, portal vein, and gall bladder are evaluated on the right side between the seventh and ninth ICS (largest visible extent of liver) and variably between the fifth to sixth and the 10th to 12th ICS. The parenchymal pattern of the normal liver consists of numerous fine, homogeneous echoes (Figure 5.4). On cross-section, the caudal vena cava is triangular in shape and is visualized in approximately 75% of goats in the 11th and 12th ICS. The portal vein always has a more ventral position and is closer to the liver surface compared with the caudal vena cava. It is circular to oval in cross section, with stellate ramifications into the liver parenchyma, and typically is visualized in all ICS in which liver is visible. The gall bladder is variable in shape and size, depending on amount of bile present and is visualized in most goats from the 9th to 10th ICS. ²⁸ The spleen is visualized on the left side from the 11th and 12th ICS, situated between the rumen and abdominal wall. The parenchymal pattern consists of numerous, homogeneous, weak echogenic shadows. ²⁹ Description of ultrasonography of the urinary and female and male genital tracts can be found in Chapters 12 and 8, respectively. ³⁰

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780323624633000141

Symbiotic Systems

T. Fenchel , ... T.H. Blackburn , in Bacterial Biogeochemistry (Third Edition), 2012

Symbiotic Digestion in Mammals

There are two principle types of symbiotic digestion in mammals: pregastric and postgastric fermentation. In the former, the fermentation chamber (the rumen) occurs before the stomach proper in an extension of the esophagus. Thus, food constituents (carbohydrates, proteins) are mostly converted into volatile fatty acids+microbial cells, and acid digestion takes place afterwards in the true stomach. The volatile fatty acids are absorbed and constitute the main carbon source for host metabolism (acetate is used primarily for energy and propionate primarily for biomass via gluconeogenesis). The necessary amino acids derive from the digestion of microbial cells, and vitamin supply is often dependent on microbial synthesis.

In postgastric fermentation, the food first undergoes acid digestion in the stomach and products of hydrolysis and soluble sugars are absorbed. A prolonged colon or a caecum (or both) then functions as a fermentation chamber in which undigested plant polymers are converted into volatile fatty acids, which are subsequently absorbed by the animal. Postgastric fermentation is more widespread than pregastric fermentation. This, perhaps, is because it was easier to evolve: all animals harbour microbial biota in their hind gut and even humans probably benefit slightly from bacterial metabolites in this way. Kangaroos and colubine monkeys are unique in that they have pre- as well as postgastric fermentation systems.

The rumen system of cows and sheep is the most studied type of pregastric fermentation, but it is probably representative of other examples. The rumen is an extension of the esophagus and constitutes about 15% of the volume of the animal. It is followed by a smaller part, the omasum, which mainly serves for the absorption of solutes, especially volatile fatty acids. After the omasum the material passes into the abomasum which is the true stomach; acid digestion takes place here. The remaining intestinal tract is no different from that found in other mammals.

The rumen content is almost neutral due to the buffering capacity of the bicarbonate containing saliva; it is also strongly reducing (E _h ~−350   mV). The bulk of the material is anaerobic, but some oxygen diffuses through the rumen wall and at times traces of oxygen can be detected. The rumen contains a complex mixture of rumen liquid and particulate material derived from plant tissue and microbes, including up to 10¹¹ bacteria and 10⁶ protozoa per millilitre. Ruminants may sometimes regurgitate part of the particulate material for further mechanical maceration of plant fibres. Carbohydrates including cellulose and hemicelluloses are effectively hydrolyzed and fermented, principally into acetate, propionate and butyrate+CO₂ and CH₄ (Fig. 9.1). Lipids are hydrolyzed; the resulting glycerol is fermented and the fatty acids are hydrogenated mainly to stearic and palmitic acids. Proteins are deaminated and fermented. Lignin, however, is not degraded and can be used as a conservative constituent for estimating digestion efficiency of e.g., cellulose.

Figure 9.1. The principle carbohydrate fermentation pathways in the rumen and the approximate stoichiometry of the overall process.

These processes result from the concerted activities of a number of physiological types of bacteria and protozoa. More than 100 species of bacteria have been isolated from the rumen, but they are not necessarily all specific for this habitat. Cellulolytic bacteria constitute a relatively small fraction of the bacterial biota: 5–15% in spite of the fact that cellulose may constitute 30–40% of the food. The reason may be that cellulolytic bacteria excrete cellulases so that some of the resulting sugars are used by other bacteria; cellulolytic bacteria may also depend on syntrophic interactions with other bacteria. Important cellulolytic bacteria include Ruminococcus, Bacteroides and Butyrovibrio, which may also be responsible for the deamination and fermentation of proteins. Selenomonas and Streptococcus bovis ferment the easily degradable carbohydrates (soluble sugars, starch). Anaerovibrio lipolytica ferments glycerol. Many rumen bacteria that use the fermentative pathway normally leading to propionate (Bacteroides succinogenes, B. amylophila) tend to produce succinate as a terminal metabolite rather than decarboxylating it to propionate. Succinate is then an important intermediate which is decarboxylated to propionate by Veillonella gazogeneous.

Many microorganisms, for example different cellulose degraders (which even include some protozoa and chytrids) seem functionally redundant. However, there is evidence for niche diversification among them. Thus, it has been found that different cellulolytic bacteria have differential attachment mechanisms and tend to attach to different sites on degrading plant material (Bath et al., 1990); also differential substrate affinities and growth yields may confer differential fitness according to substrate availability.

Hydrogen is removed through H₂/CO₂ methanogenesis in the rumen by Methanobacterium ruminantium. This process maintains a low H₂-tension in the rumen and so fermentation leads to relatively oxidized end-products. Methane production amounts to about 10% of the fermented carbon and represents a necessary loss to the ruminant, which rids itself of the gas through belching. Since methane production decreases carbon flow to the host ruminant and also contributes significantly to atmospheric methane loading, several approaches have been pursued with limited success to decrease rates of methanogenesis.

The metabolic pathways in the rumen include a number of intermediate compounds that are released into the rumen by some microbes and utilized by others; in particular, H₂ is maintained at a low concentration with a very rapid turnover (Table 9.3). Intermediates such as lactate and ethanol normally play only a small role, and they are then rapidly fermented on to acetate, butyrate, or propionate. However, if the typical coarse ruminant fodder is abruptly replaced by feed with a high starch content (e.g., grains), the high level of lactate produced (e.g. by Streptococcus bovis) can dramatically decrease pH, inhibit further metabolism by rumen bacteria, and eventually lead to lethal acidiosis. This occurs because when large amounts of readily degradable carbohydrates are available, the rapidly-dividing lactate acid bacteria are competitively superior and shift the yield of fermentation products. A more gradual change to a starch-rich diet does not have this detrimental effect. The reason is that the microbial community is normally substrate limited, energy efficient modes of fermentation are favoured, and small amounts of lactate are rapidly fermented.

Table 9.3. Turnover of Intermediates in Rumen Fermentation (After Hungate 1975)

Intermediate	Concentration (nmol   ml−1)	Turnover (min−1)	Product	Product Accounted for (%)
Lactate	12	0.03	Propionate+	7
			Acetate	1
Ethanol	trace	0.003	Acetate	?
Succinate	4	10	Propionate	33
H2	1	710	Methane	100
Formate	12	10	H2	18

A generalized scheme of rumen fermentative pathways is shown in Fig. 9.1 together with an approximate stoichiometric account of the various processes. Comparison with the previous discussion on communities of fermenting bacteria (Chapter 1 and Fig. 1.4) shows that anaerobic degradation is incomplete. In the absence of other electron acceptors, such as sulfate or nitrate, complete anaerobic degradation of carbohydrates would lead to a stoichiometric production of CO₂ and CH₄. Obviously, this would deprive the host of the carbon and energy it needs. The extent to which ruminant fermentation yields volatile fatty acids versus methanogenesis is controlled by the residence time of material in the rumen, which is a function of animal feeding rates. The residence time (about 15 hours for rumen fluid, longer for particulates) is sufficiently slow to allow for growth of hydrogenotrophic methanogens, but too fast to support growth of acetoclastic methanogens and propionate fermentors. In this context, the rumen differs significantly from the fermentative systems of freshwater sediments, in which residence times are effectively long, allowing for methanogenic conversion of acetate.

The rumen is often compared to a continuous culture, such as a chemostat. This is inaccurate because in a chemostat all constituents have the same turnover time. In a chemostat, a high dilution rate means a low efficiency of substrate conversion due to a low steady state density of microbes whereas a low dilution rate means that substrates are converted efficiently, but at a slow rate. The ruminant must maximize effective substrate conversion – but not all the way to CH₄+CO₂. This is accomplished by differential retention times for different constituents of the rumen. The rumen is compartmentalized into lobes, and material is moved between them by muscular action. In this process, material is strained and larger particles are retained longer whereas the liquid part has a shorter residence time. The microbiota are also maintained longer in the rumen relative to the liquid because the microbes are to a large extent attached to particulate matter or to the rumen wall, and this allows for a larger steady-state population density. A complete understanding of rumen metabolism must therefore include the hydraulics and mechanics of the rumen.

Rumen microbes preferentially use ammonia as a nitrogen source (Blackburn, 1965). Ammonia derives in part from amino acid deamination and in part from urea, which is supplied with saliva and degraded to NH₄ ⁺ and CO₂ by certain rumen bacteria. The nitrogen source of the ruminant is constituted by rumen microbes that are digested in the abomasum and the duodenum. Mammals excrete excess nitrogen in the form of urea. In ruminants up to 50% of the urea thus formed is excreted into the saliva. It is thus recycled to supply rumen microbes with nitrogen; this constitutes a mechanism for preserving nitrogen in animals that live on a nitrogen-depleted diet. Bacteria that have the potential to fix N₂ are present in the rumen, but nitrogen fixation is not believed to be important in the nitrogen budget.

Newborn ruminants do not have rumen microbes; they are acquired when the animals start to feed on plant material, and thus ingest saliva containing rumen microbes that have been deposited by adults. Ruminants without microbes can be reared experimentally, but these animals cannot survive on their normal plant diet. In the normal animal, eukaryotic microorganisms as well as bacteria play a role as cellulose decomposers and as a protein source. In ruminants without protozoa, but with a normal bacterial community, bacterial densities are increased and the animals are not adversely affected and – according to some reports – may show enhanced growth.

Ruminants originated relatively recently during the Miocene, and this is usually considered as an evolutionary response to the simultaneous origin of grasses. These events have had a profound effect on terrestrial ecosystems. Rumen microbiology is reviewed in Dougherty, 1965; Hungate, 1975; Hobson, 1997; Kamra, 2005.

Postgastric fermentation is often considered to be more primitive and less efficient than pregastric fermentation. Mammals with hindgut fermentation include perrissodactyls, lagomorphs, rodents, manatees, elephants, and some primates and marsupials. They are less effective on a roughage diet than are ruminants. On the other hand, they do not require a very voluminous fermentation chamber and they can utilize some constituents of the food such as proteins and vitamins directly without depending on microbial synthesis, while cellulose and hemicelluloses are still utilized relatively efficiently. The microbiology of carbohydrate degradation and metabolism in the colon or a caecum is quite similar to that of the rumen. Postgastric fermentation in mammals is treated in Janis, 1976 and Murray et al., 1977.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780124158368000098

Microbiome influences on host immunity

E.J. DePeters , L.W. George , in Immunology Letters, 2014

1 Introduction

The aim of this invited mini-review is to summarize the information available related to rumen transfaunation. Even though the method has been practice for decades [1] and is a common medical practice in food animal medicine to treat simple indigestion of ruminants [2–8], there is a paucity of scientific information to describe its benefits.

The ruminant can be considered to be a superorganism because it has a symbiotic relationship of life between the cells of the animal's body and the rumen microbes. Factors affecting the viability of microorganisms in the reticulo-rumen as well as anywhere along the gastro-intestinal tract of the ruminant impact the host animal.

Ruminants are mammals (Class – Mammalia) in the Order Arteriodactyla (even toed, hooved mammals) Suborder Ruminantia. Ruminant, from the Latin word ruminare, means to chew over gain hence the designation of cud chewing. Ruminants have a stomach with four compartments or chambers – reticulum, rumen, omasum, and abomasum ( Fig. 1). The reticulum, rumen, and omasum are lined with non-glandular mucous membranes while the abomasum, the gastric compartment, is lined with glandular mucosa. The abomasum is similar in function to the human stomach. The largest compartment is the rumen, which along with the reticulum, serve as sites of anaerobic fermentation. There are coronary grooves in the rumen creating sacs. There is a cranial groove that separates the reticulum and rumen, and in cattle, sheep, and goats the two compartments are easily distinguished with the reticulum having a honey combed appearance. These compartments are lined with finger like projections called papillae that absorb nutrients (e.g. volatile fatty acids produced by the rumen microbiota). These finger-like projects are nature's way of increasing the absorptive surface area of the reticulum and rumen. Often ruminant nutritionists refer to these compartments as the reticulo-rumen because together they function in the rumen cycle (coordinated contractions) to support the acts of eructation and rumination. The contractions of the rumen cycle inoculate new food with microorganisms, distribute the end products of digestion for absorption by the mucosa papillae, and pass digesta to the omasum. Eructation is the process by which ruminants release gases from the reticulo-rumen that are produced during anaerobic fermentation. Eructation is a quiet process that involves eructated gas passing up the esophagus and into the trachea and the lungs to be respired. Rumination involves bringing a bolus of digesta up the esophagus (regurgitate) into the mouth where the bolus of digesta (cud) is chewed. The cud is eventually re-swallowed and the process continues with another bolus regurgitated for cud chewing (crushing and grinding of particles by the molars). Cud chewing increases surface area of the feed particles, in particular fibrous material, to enhance microbial digestion. The act of cud chewing also stimulates salvia production, and the buffers present in the saliva help to maintain rumen pH when the bolus is re-swallowed. Digesta leaves the reticulum via the reticulo-omasal orifice. The omasum, with its many leaves or laminae, controls flow of digesta to the abomasum. The abomasum is the gastric, glandular compartment similar to the stomach of nonruminants (human, pig, mouse) with secretion of acid (HCl) and pepsinogen and a pyloric sphincter that regulates flow of digesta from the abomasum to the duodenum.

Fig. 1. Ruminant stomach. http://biobook.nerinxhs.org/bb/systems/digestion/1000px-Abomasum-ia-omaso.svg.png.

Transfaunation in its current use includes a broad spectrum of microorganisms including bacteria, protozoa, fungi, and archaea that are transferred from rumen of a donor to the rumen of a recipient. In his seminal book on rumen microbiology, Hungate [9] stated that transfaunation of protozoa occurred when protozoa that were left on food by one animal were consumed by another animal. Young animals were faunated by their mothers when she licked them. It is not clear based on our reading of the literature where the term 'transfaunation' originated or how it was derived.

One dictionary definition of transfaunation is "transfer of symbiotic fauna (usually mutualistic protozoa) from one host to another". Originally protozoa were defined as unicellular protists. Some ciliated protozoa have the ability to move similar to animals. Protozoa are also eukaryotic while bacteria are prokaryotic. Defaunation of the rumen referred to elimination of protozoa [9]. One dictionary definition of defaunate is "elimination of microscopic fauna, especially protozoa, in the rumen and cecum, with depressing effects on digestion". Although the meaning of transfaunation is not clearly defined in the literature, in this review we will use the term transfaunation broadly. The discussion of rumen transfaunation will include both microflora and to a limited extent chemical constituents in the rumen contents.

Read full article

URL:

https://www.sciencedirect.com/science/article/pii/S0165247814001011

smithalch1955.blogspot.com

Source: https://www.sciencedirect.com/topics/medicine-and-dentistry/omasum