Lecture No. 22. Features of digestion in ruminants.
In ruminants the stomach is complex, multi-chambered, includes four sections - the rumen, the mesh, the book and the abomasum. The first three sections are called forestomach, and the abomasum performs the function of a single-chamber glandular stomach. The mucous membrane of the proventriculus is covered with flat stratified keratinizing epithelium and does not contain secretory digestive glands.
In the proventriculus of ruminant animals, ideal conditions are created for the growth, development of microorganisms and hydrolysis of feed nutrients under the action of bacterial enzymes:
1. Regular supply of food (5 – 9 times a day).
2. Sufficient amount of liquid ( drinking water, saliva).
3. Repeated chewing (rumination) of the feed increases the surface area and availability of feed nutrients for microorganisms.
4. Soluble waste products of microorganisms are easily absorbed into the blood or transferred to other parts of the stomach without accumulating in the rumen.
5. Ruminant saliva is rich in bicarbonate; due to it, the volume of liquid, the constancy of pH and ionic composition are mainly maintained. About 300 g of NaHC0 3 enters the rumen per day. It also contains a significant amount of urea and ascorbic acid, which have an important role for the life of symbiont microflora.
6. Constant gas composition with low oxygen content.
7. The temperature in the rumen is maintained within 38 0 - 42 0 C, and at night it is higher than during the day.
Tripe - Rumen - The largest fermentation chamber in terms of volume is the forestomach. At the large cattle rumen capacity is up to 200 liters, sheep and goats - about 20 liters. The greatest development of the rumen begins after the young animals move to mixed nutrition using roughage. On the mucous membrane of the scar, papillae of different sizes are formed, increasing its absorption surface. The powerful folds present in the scar divide it into dorsal and ventral sacs and blind protrusions. These folds and muscle cords, during contractions of the rumen, ensure the sorting and evacuation of contents to the underlying sections.
Mesh - Reticulum - a small round-shaped compartment with a capacity of 5 - 10 liters for cows and 1.5 - 2 liters for sheep and goats. The mesh is separated from the vestibule of the scar by a crescent-shaped fold, through which only crushed and partially processed contents of the scar pass. On the mucous membrane of the mesh there are cells protruding above its surface that sort the contents there. Therefore, the grid should be considered as a sorting organ. Small, processed particles by contractions of the mesh enter the next sections of the stomach, and larger ones pass into the rumen for further processing.
Book – Omasum - the mucous membrane forms sheets of different sizes (large, medium, small), between which larger particles of feed are retained for additional grinding, and the liquefied part of the contents passes into abomasum. Thus, the book is a kind of filter. In the book, although to a lesser extent than in the rumen and mesh, the processes of hydrolysis of nutrients by microbial enzymes continue. It actively absorbs 50% of the incoming water and minerals, ammonia and 80–90% of VFAs.
Abomasum – Abomasum - The mucous membrane of the rennet contains glands that produce rennet juice. During the day it is formed: in cows - 40 - 80 liters, in heifers and bulls - 30 - 40, in adult sheep - 4 - 11 liters. rennet juice whose pH ranges from 0.97 to 2.2. As in monogastric animals, the most important components of rennet juice are enzymes (pepsin, chymosin, lipase) and hydrochloric acid. One of the significant features of rennet digestion is the continuous secretion of rennet juice due to the constant entry into the abomasum of a previously prepared homogeneous mass from the proventriculus.
Esophagus enters the stomach at the border between the mesh and the vestibule of the scar and then continues along the wall of the mesh to the entrance to the book as an esophageal groove in the form of a semi-closed tube. The esophageal gutter is well developed in young animals and ensures the flow of milk, bypassing the forestomach (which is not yet developed and not functioning) directly into the abomasum. With the beginning of milk intake, irritation of the oral cavity receptors and a reflex closure of the esophageal groove ridges occurs. Sucking movements increase the closure of the ridges of the esophageal gutter, so in the first days it is recommended for young animals to drink milk through a nipple drinker. In this case, the milk in the oral cavity mixes well with saliva and a loose milk clot is formed in the abomasum, available for further digestion. When milk is quickly swallowed in large portions, the gutter does not have time to close and part of the milk enters the proventriculus, which can lead to significant disruption of the digestive and other functions of the body.
From the 20th–21st day, the young animals begin to take roughage and the importance of the esophageal gutter gradually decreases. From this time on, the forestomachs begin to function and are populated by microflora. Until 3 months of age, calves experience a peculiar transition period from digestion in the abomasum to digestion in the proventriculus. By 6 months, the proventriculus reaches its full development and the type of digestion characteristic of adult animals is established in calves, when the hydrolysis of nutrients is carried out by microbial enzymes.
State of the forestomach at 6 weeks of age with different types feeding.
Calves are born with underdeveloped forestomachs. Therefore, it is necessary to start stimulating rumen activity as early as possible. This will shorten the period of drinking and switch to plant foods earlier. This is important, including from an economic point of view. Already from 3-5 days it is necessary to offer calves high-quality concentrated feed. When grain is digested, acids are formed that promote the activity of the rumen and rumen microflora more strongly than mechanical stimulation with roughage, as previously thought. Feeding hay does not have the same effect as feeding concentrates. This can be seen in the following images:
In the proventriculus, microorganisms find favorable conditions for their life activity and reproduction. Only 1 g of rumen content contains up to 1 million ciliates and 10 10 bacteria. Rumen microorganisms are represented mainly by bacteria, protozoa single-celled organisms and fungi. Their quantity and species composition depend on the composition of the diet, so new foods should be included in the diet and the transition from one diet to another should be gradual.
The importance of microorganisms in the digestion of ruminants.
1. The ability to obtain energy from complex carbohydrates contained in fiber and in the fibrous structures of plants.
2. Possibility of compensating for protein and nitrogen deficiency. Rumen microorganisms have the ability to use non-protein nitrogen to form protein in their own cells, which is then used to form animal protein.
3. Synthesis of B vitamins and vitamin K.
Microflora represented by gram-positive and gram-negative bacteria, anaerobic by type of respiration, about 150 species. Based on their participation in digestive processes and the substrate used, groups of cellulolytic, proteolytic and lipolytic bacteria can be distinguished. Between various types bacteria, complex forms of relationships are established. Symbiont relationships between different species of bacteria allow them to cooperate in the use of metabolites of one species by bacteria of another species. Based on their image and place of residence, they distinguish between bacteria associated with the rumen wall, located on the surface of its mucous membrane, bacteria fixed on the surface of solid particles of feed and bacteria free-living in the rumen contents.
Microfauna (protozoa) are represented by a variety of (about 50 species) ciliates (class ciliate). Some authors identify up to 120 species of rumen protozoa, including 60 species in cattle, and up to 30 species in sheep and goats. But one animal can have 14–16 species at the same time. Ciliates reproduce quickly and can produce up to five generations per day. The species composition and number of ciliates, as well as bacteria, depend on the composition of the diet and the reaction of the rumen contents. The most favorable environment for their life is an environment with a pH of 6 – 7.
The importance of ciliates is that, by loosening and grinding, they subject the food to mechanical processing, making it more accessible to the action of bacterial enzymes. Ciliates absorb starch grains and soluble sugars, protecting them from fermentation and bacterial breakdown, and ensure the synthesis of proteins and phospholipids. Using nitrogen for your life plant origin, ciliates synthesize the protein structures of their body. Moving along with the contents through the digestive tract, they are digested, and the animals receive a more complete protein of microbial origin. According to V.I. Georgievsky, the biological value of bacterial protein is estimated at 65%, and protozoan protein at 70%.
Digestion of carbohydrates.
Carbohydrates make up 50–80% of plant food. These are polysaccharides: cellulose, hemicellulose, starch, inulin, pectin substances and disaccharides: sucrose, maltose and cellobiose. Digestion of fiber in the forestomach increases slowly and reaches a maximum after 10 - 12 hours. The intensity of breakdown depends on the content of lignin in the feed (part of the structure cell membranes plants). The more lignin in plant foods, the slower the fiber is digested.
Digestion of starch. Starch ranks second after fiber in the carbohydrate diet of ruminants. The rate of starch digestion depends on its origin and physicochemical properties. Almost all monosaccharides supplied with feed or formed in the rumen during the hydrolysis of polysaccharides are utilized by microorganisms. Some of the hydrolysis products (lactic acid, succinic acid, valeric acid, etc.) are used by microorganisms as a source of energy and for the synthesis of their cellular compounds.
Carbohydrates subjected to hydrolysis are further fermented with the formation of low molecular weight volatile fatty acids (VFA) - acetic, propionic, butyric, etc. On average, up to 4 liters of VFA are formed per day. The VFA ratio depends on the composition of the diet.
Feeds of plant origin with a high fiber content (hay) provide more acetic and propionic acids, and concentrated ones - acetic and butyric acids.
Table. Percentage of main VFAs in the content
cow rumen
| Type feeding | Acid,% |
||
| vinegar | propionic | oil |
|
| Concentrated Juicy Hay | |||
Absorbed acids are used by the body for energy and plastic purposes. Acetic acid is a precursor of milk fat, propionic acid is involved in carbohydrate metabolism and is used for the synthesis of glucose, butyric acid is used as an energy material and is used for the synthesis of tissue fat.
Protein digestion. The protein content in plant feed is relatively low, ranging from 7% to 30%. These are simple proteins: albumins, globulins, prolamins and histones; complex proteins: phosphoproteins, glucoproteins, chromoproteins. In addition, plant feed contains free amino acids and other nitrogenous compounds: nitrates, urea, purine bases, etc. Plant proteins that enter the rumen are broken down by enzymes of proteolytic microorganisms into peptides, amino acids and ammonia. In the rumen, ammonia is absorbed into the blood and it enters the liver, where it is converted into urea, which is partially excreted in the urine and partially in saliva. A significant part of ammonia, by diffusion from the blood through the wall of the rumen, returns to its cavity and continues to participate in nitrogen metabolism.
Simultaneously with the processes of breakdown of plant protein in the rumen, the synthesis of bacterial protein of high biological value occurs. Non-protein nitrogen can also be used for this purpose. The absorption of non-protein compounds (urea) by nitrogen is based on a microbiological process. It has been revealed that in the rumen, urea (carbamide) is quickly hydrolyzed by microorganisms to form ammonia, which they use for further synthetic processes.
Feeding urea does not cause complications if the doses are not too high. It is better to feed urea to two or three cottages in a mixture with other feeds. When feeding nitrogen-containing substances of non-protein origin, the diet must be balanced in terms of the content of easily digestible carbohydrates, otherwise a large number of ammonia, which cannot be fully used by microorganisms and in these cases, dysfunction of the kidneys, liver and other organs may occur.
Digestion of lipids. Plant foods contain relatively little fat - 4 - 8% of dry matter. Crude fat is a complex mixture of components: triglycerides, free fatty acids, waxes, phospholipids and cholesteryl esters. The amount of lipids in the diet of ruminants is usually small. Vegetable fats contain up to 70% unsaturated fatty acids. Under the influence of enzymes of lipolytic bacteria, fats in the rumen undergo hydrolysis to monoglycerides and fatty acids. Glycerol in the rumen is fermented to form propionic acid and other VFAs. Fatty acids with a short carbon chain are used for the synthesis of lipids in microbial bodies, and with a long one they enter other parts of the digestive tract and are digested.
Formation of gases in the rumen. During the fermentation of feed in the rumen, in addition to volatile fatty acids, gases are formed (carbon dioxide - 60 - 70%, methane - 25 - 30%, hydrogen, nitrogen, hydrogen sulfide and oxygen about - 5%). According to some reports, large animals produce up to 1000 liters of gases per day. The largest amount of gases is formed when consuming easily fermentable and succulent feeds, especially legumes, which can lead to acute rumen swelling (tympany). Gases formed in the rumen are removed from the body mainly by regurgitation of food during chewing. A significant part of them is absorbed in the rumen and transported by the blood to the lungs, through which they are removed with exhaled air. Carbon dioxide is removed to a greater extent through the lungs and methane to a lesser extent. Some of the gases are used by microorganisms for further biochemical and synthetic processes.
Motility of the forestomach. The smooth muscle tissue of the proventriculus performs enormous mechanical work in mixing, grinding, squeezing out gases and evacuating contents. Abbreviations individual parts forestomachs are coordinated with each other. Each cycle begins with mesh reduction. The grid contracts every 30 - 60 s. There are two phases: first, the mesh decreases in size by half, then relaxes slightly, after which it contracts completely. When chewing gum, an additional third contraction occurs. When the mesh contracts, coarse large particles of content are pushed back into the rumen, and the crushed and semi-liquid food mass enters the book and then into the abomasum.
Normally, the scar contracts 2-5 times every 2 minutes. In this case, a sequential reduction of its sections occurs - the vestibule of the scar, the dorsal sac, the ventral sac, the caudodorsal blind protrusion, the caudoventral blind protrusion, and then again the dorsal and ventral sacs. Contraction of the dorsal sac is accompanied by regurgitation of gases. The book contracts in the transverse and longitudinal directions, due to this additional maceration of the retained coarse feed particles occurs. Between the leaves of the book, coarser particles of food undergo further digestion.
Ruminant process. The presence of the chewing gum process is characteristic feature digestion in ruminants is the regurgitation of part of the dense contents of the rumen and its repeated chewing. The ruminant period begins some time after eating, depending on the nature of the food and external conditions: in cattle after 30 - 70 minutes, in sheep after 20 - 45 minutes. During this time, the food in the rumen swells and partially softens, which makes it easier to chew. The ruminant period begins faster with complete rest in a lying animal. At night, ruminant periods occur more often than during the day. There are 6 - 8 ruminant periods per day, each of which lasts 40 - 50 minutes. During the day, cows chew up to 100 kg of rumen contents.
At the beginning of regurgitation, additional contraction of the mesh and the digestive gutter occurs, as a result of which the liquid contents of the mesh rise to the cardial opening of the esophagus. At the same time, breathing stops during the exhalation phase, followed by an attempt to inhale with the larynx closed. In this regard, the pressure in chest cavity drops sharply to 46 - 75 mm Hg. Art., which leads to the absorption of the liquefied mass into the esophagus. Then breathing is restored and antiperistaltic contractions of the esophagus promote the movement of the food coma through the esophagus into oral cavity. After the regurgitated mass enters the oral cavity, the animal swallows the liquid part in small portions, and chews the dense part remaining in the oral cavity thoroughly.
Regulation of the ruminant process carried out reflexively from the receptor zones (baro-, tango- and tensioreceptors) of the mesh, esophageal gutter and scar. The center of chewing gum is located in the nuclei of the medulla oblongata. The reticular formation of the medulla oblongata, the hypothalamus and the limbic cortex take part in the regulation of ruminant processes.
The mucous membrane of the rennet contains glands that produce rennet juice. A fairly large amount of rennet juice is formed per day: in cows - 40 - 80 liters, in heifers and bulls - 30 - 40, in adult sheep - 4 - 11 liters. With each feeding of the animal, secretion increases. In sheep, the pH of the juice is 0.97 - 2.2, in cows -1.5 - 2.5. As in monogastric animals, the most important components of rennet juice are enzymes (pepsin, chymosin, lipase) and hydrochloric acid. One of the significant features of rennet digestion is the continuous secretion of gastric juice due to the constant supply of a previously prepared homogeneous mass into the abomasum. This state of the abomasal glands is maintained by constant irritation of the mechano- and chemoreceptors of the abomasum itself and the interoceptive influence of the proventriculus.
The humoral phase of rennet secretion is carried out with the participation of hormones and metabolites of the digestive tract (gastrin, enterogastrin, histamine, etc.). In regulation secretory activity abomasum hormones are involved thyroid gland, adrenal glands, pancreas, gonads, etc. Depending on the type of feed, different quantities rennet juice. The largest amount of it with high acidity and digestive ability is formed when feeding grass and hay, legumes, grain feed and cake.
Structure of the stomach of ruminants. The digestive system of ruminants is adapted to receive and process large quantities of relatively low-nutrient, bulky feed. The ability to digest large quantities of roughage in ruminants is more pronounced than in other animals, due to the complex multi-chamber stomach.
Stomach of ruminants by structure and functional features differs significantly from the stomach of carnivores, omnivores and horses. The stomach of ruminants is four-chambered. Its first three sections - the scar, the mesh and the book - are called the proventriculus. The forestomach does not have glands. The fourth section, the abomasum, is a true glandular stomach, similar to the stomach of a dog. The volume of the proventriculus is over 100 liters. Food masses accumulate in the forestomach, and chemical and biological processing of feed occurs.
The largest of the forestomachs is the rumen. With several incomplete interceptions, the scar is divided into three parts: the upper and lower sacs and the vestibule. At the threshold of the scar, the esophagus opens. The mesh is an oval-shaped bag. The mucous membrane of the mesh forms cells like a honeycomb with numerous folds of various sizes. At the top, the mesh communicates with the scar, and at the bottom - with the book.
The book is spherical in shape, somewhat flattened on the sides. The book has a large number of folds in the form of leaves of different sizes. The leaves are covered with horny papillae adapted for grinding food. The book acts as a final filter, retaining coarse parts of the feed with its leaves.
There are also some features in the structure of the esophagus. The esophagus of ruminants in the lower part passes into the esophageal groove, or semi-closed tube. The esophageal gutter passes through; tripe, mesh up to the book. Within the vestibule of the scar, it is limited by thickening of the mucous membrane in the form of ridges, the so-called lips. These thickenings contain muscles and nerves.
In calves and lambs, when drinking milk and water, the muscles of the lips of the esophageal gutter contract and close, resulting in the formation of a tube that serves as a continuation of the esophagus. The closing of the lips of the esophageal gutter coincides with the act of swallowing, is a continuation of peristalsis of the esophagus and is regulated by the nervous system.
Slow drinking of milk, especially with the help of a nipple drinker, ensures normal closure of the esophageal gutter. In this case, the milk is sent directly to the abomasum. When drinking quickly in large sips, the lips and esophageal gutter do not close completely and the milk partially enters the rumen, where it can rot, since the rumen is not yet functioning in the first days of the animal’s life.
By 9-10 months of age, the reflex of closing the esophageal gutter fades, the lips of the esophageal gutter lag behind the proventriculus in growth, its walls become coarser, so in adult animals not only roughage, but also liquid food partially ends up in the rumen.
Microflora of the stomach. In the proventriculus of ruminants, a significant part of the feed is digested without the participation of special digestive enzymes. The digestion of feed here is associated with the vital activity of numerous and diverse microflora that enter the rumen along with food. The constancy of the composition of the liquid medium and the optimal temperature in the rumen ensure high vital activity of the microflora. Currently, three main groups of rumen microorganisms have been identified: bacteria, ciliates and fungi. There are especially many ciliates in the rumen.
With normal feeding, 1 mm 3 of rumen contents contains up to 1000 ciliates. They take part in the digestion of fiber. There are more than 30 species of ciliates in the rumen. The number of bacteria is about 109-1016 in 1 ml. When feeding animals with concentrated feed, the number of bacteria increases. Despite the small size of the bacteria, their total volume is equal to the volume of ciliates. Each of these groups has a numerous number of species. The species composition largely depends on the nature of the food. When the diet changes, the species composition of the microflora also changes. Therefore, for ruminants, a gradual transition from one diet to another is of particular importance, which allows the microflora to adapt to the nature of the feed.
In the rumen, well-chopped, swollen feed undergoes fermentation and breakdown under the influence of ciliates, bacterial and plant enzymes. Under the influence of the cellulose enzyme contained in feed and secreted by rumen bacteria, the walls plant cells are destroyed. Bacterial fermentation of fiber occurs, resulting in the formation of many gases (carbon dioxide, methane, ammonia, hydrogen) and volatile fatty acids (acetic, propionic, butyric and lactic). Gases are removed from the forestomach during belching. Easily fermentable and poor-quality feed produces a lot of gases during fermentation, which sometimes causes rumen swelling.
In the rumen, microorganisms synthesize amino acids from carbohydrates, ammonia and fatty acids. At the same time, microorganisms can use urea nitrogen and; ammonia water for the synthesis of amino acids and protein. Therefore, ruminants are often given nitrogen-containing non-protein feed additives - urea CO(MH2)2 or urea, ammonium salts and ammonia water. In the rumen, urea, under the influence of the enzyme urease secreted by rumen bacteria, reacts with water and breaks down. Ammonium salts are also resolved by rumen bacteria.
When adding nitrogen-containing non-protein to the feed feed additives Ammonia accumulates in the rumen. Rumen bacteria use ammonia to synthesize amino acids (cystine, methionine, lysine, etc.), and from them biologically, complete proteins. Thus, thanks to the vital activity of rumen microorganisms, plant proteins are converted into complete proteins of the animal body.
Non-ruminant animals cannot use urea, ammonium salts and ammonia water, since their single-chamber stomach does not contain bacteria. Therefore, if there is a lack of biologically complete proteins in the feed, synthetic essential amino acids - methionine, lysine, etc. - are introduced into the diet of pigs and poultry.
In the rumen, not only fiber is fermented, but also starch, sugars and other substances, which leads to the formation of large amounts of low molecular weight fatty acids - acetic, propionic and butyric. These acids are absorbed by the rumen wall, enter the blood and serve as the starting material for the formation of glycogen (animal starch). It has now been established that during the stay of food masses in the rumen, about 70-85% of the digestible dry matter is absorbed. Fermentation processes in the rumen prevail over other digestive processes in the digestive tract.
The intensity of fermentation processes in the rumen is very high. In an adult sheep, as a result of fermentation, from 200 to 500 g of organic acids are formed per day. These acids are already absorbed into the blood in the forestomach.
Ruminant period. Ruminant animals, when eating food, make only a few chewing movements necessary to form a food coma. In the rumen, the feed is fermented and then regurgitated in small portions into the oral cavity for more thorough chewing. If when eating an animal makes several chewing movements, then when chewing a food coma that comes from the rumen, it makes 70-80 chewing movements.
This method of processing food in ruminants was formed in connection with the use of coarse, difficult-to-digest plant foods containing large amounts of fiber, which requires careful processing. And therefore the food is chewed twice: first hastily, just to grab more of it, and then very carefully in a place safe from predators. This method of nutrition gave the wild ancestors of modern ruminants advantages in the struggle for existence.
The ruminant period is a biological adaptation that allows animals to quickly fill the rumen with poorly chewed food, and chew it thoroughly in between meals. In calves, the ruminant period begins approximately in the third week of life, i.e., when the animals begin to consume roughage. By this period, conditions for fermentation processes are created in the rumen.
The ruminant period begins 40-50 minutes after feeding. During this time, the feed in the rumen loosens, swells and fermentation processes begin. The onset of the ruminant period is delayed high temperature environment.
The ruminant period begins when the contents of the rumen are liquefied. Drinking water speeds up the onset of the ruminant period. The easiest time for the ruminant period to occur is when the animals are at rest, in a lying position. As a rule, there are 6-8 ruminant periods per day, each lasting 40-50 minutes.
In ruminants that feed on rough plant food, the complex stomach consists of a rumen, mesh, book and abomasum (Fig. 96): the first three sections (rumen, mesh and book) form the so-called proventriculus and are lined with multilayered epithelium; the proventriculus is devoid of digestive glands and only bacterial fermentation occurs in it with the participation of the symbionts inhabiting it, which can only exist in a neutral or slightly alkaline environment. The decomposition of plant food by symbionts takes place in the rumen, where only lightly chewed food accumulates; fermentation intensifies after repeated chewing of the gum and wetting it with saliva, which has a slightly alkaline reaction. Fermentation and mechanical grinding of food particles continues in the mesh and book. Processing with gastric juice occurs only in the abomasum, in its acidic environment.
In sloths, the stomach serves primarily as a place for storing food; it reaches 20-30% of body weight and is always filled with food that slowly enters the intestines and moves through it at a low speed (sometimes up to a week). The complex stomach of cetaceans, whose teeth cannot crush food, ensures its mechanical processing through peristaltic movements of the walls. In anteaters, food is crushed in the pyloric part of the stomach, which has a hard cuticular lining and is equipped with highly developed muscles. The stomach juice of cetaceans and anteaters is active and decomposes (hydrolyzes) even such persistent substances as chitin, which is usually indigestible by other animals.
The digestive system of a ruminant animal may surprise the uninitiated in agricultural matters. Thus, the digestive system of cows is very voluminous, which is associated with the need to process a large amount of incoming food. A large supply of food is naturally necessary to produce a sufficient amount of dairy products. The quality of the food entering the stomach should also be taken into account, since it is usually coarse, hence the need for a large amount of time to completely break down the food.
The stomach of a cow, like that of other cattle, is structured in a very unique way. How many stomachs does a cow have, how is it structured in general? digestive system these animals? We will answer these and a number of related other questions below in this article. Each section of the stomach has its own functions. We will also focus on them.
Cows do not bother much about chewing their food, only slightly grinding the grass they eat. The main part of the feed is processed in the rumen to a fine pulp.
The digestive system of a cow, on the one hand, ideally and rationally distributes time during grazing, on the other hand, allows you to extract everything as much as possible. nutrients from roughage. If there is a cow chew thoroughly Every blade of grass she picks, she will have to stay in the pasture all day and eat grass. During rest, it is worth noting that the cow constantly chews the food that has collected in the rumen and is now being re-chewed.
Section of the stomach of ruminants
The cow's digestive system consists of several sections that differ in function, namely:
The mouth of these animals is especially interesting, since its main purpose is to pluck grass, hence the presence of exclusively the front row of lower teeth. Impressive saliva volumes, released every day, it reaches approximately 90 to 210 liters! Enzymatic gases accumulate in the esophagus.
How many stomachs does a cow have? One, two, three or even four? This will cause surprise, but there is only one, but consisting of four departments. The first and largest compartment is the scar, and the proventriculus contains a mesh and a book. No less interesting and not quite euphonious name The fourth chamber of the stomach is the abomasum. The entire digestive system of the cow requires detailed consideration. Learn more about each department.
Scar
The cow's rumen is the largest chamber and performs a number of very important digestive functions. Thick-walled tripe is not affected by rough food. Minute reduction of the rumen walls provides stirring the eaten grass, subsequently the enzymes distribute them evenly. Here, in addition, hard stems are crushed. What is a scar used for? Let us outline its main functions:
- enzymatic - intracellular bacteria give rise to digestive system, thereby ensuring the initial fermentation process. The rumen actively produces carbon dioxide and methane, with the help of which all food entering the organ is broken down. If carbon dioxide does not regurgitate, the animal’s stomach swells, and as a result, the functioning of other organs malfunctions;
- function of mixing food - scar muscles contribute to mixing food and its further release for repeated chewing. Interestingly, the walls of the rumen are not smooth, but with small formations resembling warts that promote absorption useful substances;
- transformation function - more than one hundred billion microorganisms present in the rumen contribute to the conversion of carbohydrates into fatty acids, which provides energy to the animal. Microorganisms are divided into bacteria and fungi. Protein and ammonia keto acids are converted thanks to these bacteria.
A cow's stomach can hold up to 150 kg of feed, a huge proportion of which is digested in the rumen. Up to 70 percent of the food eaten is found here. There are several bags in the rumen:
- cranial;
- dorsal;
- ventral.
Probably, each of us has noticed that a cow, some time after eating food, regurgitates it back to chew it again. A cow spends more than 7 hours every day on this process! Repeatedly regurgitation is called chewing gum. This mass is thoroughly chewed by the cow, and then ends up not in the rumen, but in another section - in the book. The scar is located on the left side abdominal cavity ruminant animal.
Net
The next section in the cow's stomach is the mesh. This is the smallest compartment, with a volume not exceeding 10 liters. The mesh is like a sieve that stops large stems, since in other sections coarse food will immediately cause harm. Imagine: a cow chewed grass for the first time, then food got into the rumen, belched, chewed again, hit the net. If the cow has not chewed thoroughly and left behind large stems, they will be stored in a net for one to two days. What is it for? The food is decomposed and again offered to the cow for chewing. And only then does the food go into another section - the book.
At the net special function- it separates large pieces of food from small ones. Thanks to the mesh, large pieces are returned back to the rumen for further processing. There are no glands in the mesh. Like a rumen, the mesh walls are covered with small structures. The grid consists of small cells that define food processing level the previous chamber, that is, the scar. There are no glands in the mesh. How is the mesh connected to other sections - the scar and the book? Very simple. There is an esophageal groove, shaped like a semi-closed tube. Simply put, the net sorts food. Only sufficiently crushed food can get into the book.
Book
The book is a small compartment that holds no more than 5 percent of the food consumed. The capacity of the book is about 20 liters. Only here the food repeatedly chewed by the cow is processed. This process is ensured by the presence of numerous bacteria and potent enzymes.
It is no coincidence that the third section of the stomach is called the book, which is associated with appearance departments - continuous folds, divided into narrow chambers. Food is located in folds. The cow's digestive tract does not end there - the incoming saliva processes the food, and fermentation begins. How is food digested in a book? Feed distributed along the folds and then becomes dehydrated. Moisture absorption is carried out due to the peculiarities of the mesh structure of the book.
The book does important function throughout digestion - it absorbs food. By her own the book is quite voluminous, but it holds a small amount of food. The book absorbs all moisture and mineral components. What is the book like? An elongated bag with numerous folds.
The book is like a filter and chopper of large stems. In addition, water is absorbed here. This department is located in the right hypochondrium. It is connected to both the mesh and the abomasum, that is, it continues the mesh, passing into the abomasum. Shell of the third section The stomach forms folds with small nipples at the ends. The abomasum is elongated in shape and resembles a pear, which is thickened at the base. Where the abomasum and book connect, one end connects to the duodenum.
Why does a cow chew her food twice? It's all about the fiber contained in plants. It is difficult and time-consuming to process, which is why double chewing is necessary. Otherwise the effect will be minimal.
Abomasum
The last section of the cow's stomach is the abomasum, similar in structure to the stomachs of other mammals. A large number of glands, constantly secreted gastric juice- features of rennet. Longitudinal rings in abomasum form muscle tissue. The walls of the abomasum are covered with a special mucus, consisting of their epithelium, containing the pyloric and cardiac glands. The mucous membrane of the abomasum is formed from numerous elongated folds. The main digestive processes take place here.
Huge functions are assigned to the abomasum. Its capacity is about 15 liters. Here the food is prepared for final digestion. The book absorbs all the moisture from the food, therefore, it enters the rennet in a dried form.
Let's sum it up
Thus, the structure of the cow’s stomach is very unique, since the cow does not have 4 stomachs, but a four-chamber stomach, which ensures the processes of the cow’s digestive system. The first three chambers are an intermediate point, preparing and fermenting the incoming feed, and only in the rennet contains pancreatic juice, completely processing food. The cow's digestive system includes rumen, mesh, book and abomasum. The enzymatic filling of the rumen ensures the process of breaking down food. The structure of this compartment resembles a similar human organ. The rumen of cattle is very capacious - 100 - 300 liters, while that of goats and sheep is much smaller - only 10 - 25 liters.
Long-term retention of food in the rumen ensures its further processing and decomposition. First, fiber undergoes breakdown, and is involved in a huge number of microorganisms. Microorganisms change depending on the food, so there should not be a sharp transition from one type of food to another.
Fiber is very important for the body of the ruminant animal as a whole, since it provides good motor skills pregastric sections. Motor function, in turn, ensures the passage of food along gastrointestinal tract. In the rumen, the process of fermentation of feed masses occurs, the mass is broken down, and the body of the ruminant animal absorbs starch and sugar. also in this department protein is broken down and non-protein nitrogen compounds are produced.
The acidity of the environment in the abomasum is provided by numerous glands located on the walls of the abomasum. The food is broken down into tiny particles, and the nutrients are then completely absorbed by the body. ready mass moves into the intestines, where the most intense absorption of all beneficial microelements occurs. Imagine: a cow eats a bunch of grass in the pasture, and the digestion process begins, which ultimately takes from 48 to 72 hours.
The digestive system of cows is very complex. These animals must continuously eat, as a break will bring big problems and will have a very negative impact on the health of the cow. Complex structure of the digestive system It has negative qualities- stomach upset is a common cause of death in cows. Does a cow have 4 stomachs? No, just one, and the entire digestive system includes the oral cavity, pharynx, cow's esophagus and stomach.
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What do cows and giraffes have in common? Why does a cow have four stomachs and a horse only one? What happens in these four stomachs? You will find answers to all these questions in this article.
We all know very well that herbivores are animals that eat plants. And, despite all the apparent simplicity, being a herbivore is not so easy.
Earthly plants contain large amounts of material that is necessary to keep them upright. Their special “reinforced concrete” is cellulose that forms structures around cell walls and which cannot be digested by animals. Which is sad, because cellulose is formed by glucose residues, which store a lot of energy.
Some insects, being small in size, have adapted use this "canned" energy. They have acquired some kind of hypodermic syringe instead of a mouth and use it to pierce the cellulose walls and suck up the internal contents of the cell. However, the harsh reality of most herbivores requires that they eat, chew and gnawing to maintain active life.
To help herbivores use the energy stored in plants, evolution gave them a special digestive apparatus: wide chewing teeth for breaking down cellulose fibers and a long and complex digestive tract that contains special types microorganisms capable of digesting cellulose. In return for the home that animals provide to bacteria, the latter supply the host with some interesting and irreplaceable substances.
Rabbits and horses are representatives first innovation in the digestive system herbivores. They have a long intestine and a set of bacteria that partially digest cellulose fibers. Rabbits even recycle their excrement by eating it, this is called secotrophy.
However, herbivores, capable of using the energy stored in plants as efficiently as possible, became ruminants. Moreover, their domestication also contributed to the success of their spread throughout the planet. Ruminant animals include:
