Instead, they only partially chew the vegetation, then microorganisms in the rumen section of the stomach break down the rest. Animals with singular stomach compartments — known as a monogastric digestive system — do not have the same capability. Many different animals have this unique four compartment stomach type of digestive system, including:.
These animals convert plant matter and vegetation into useable energy more efficiently than other herbivores. In cattle and dairy cows, the development, pH balance, functionality and bacteria levels of the digestive system are crucial to maintaining overall health and high yield. While some parts of the ruminant digestive system are similar to those of non-ruminant systems, several essential components perform the necessary functions for digestion.
While the ruminant digestive tract operates differently from the monogastric system, it is composed of the same six basic components:. The mouth is where the process begins. Cattle will graze by wrapping their tongues around plants and tearing, pulling them into their mouth for mastication. They chew first with the lower jaw incisors, working against a hard dental pad on the front part upper palate, then second with the molars, grinding plant material down further.
Chewing stimulates saliva production and the saliva mixes with plant matter before the animal swallows. Saliva contains enzymes capable of breaking down fats and starches and helps to buffer the pH levels in the reticulum and rumen segments of the stomach. Mature cattle will swallow from 50 to 80 quarts daily to aid in digestion, but the amount varies based on how much time they spend chewing.
When the cattle swallows the plant material and saliva mix, it will travel down the esophagus to the rumen. The esophagus performs the swallowing action through waves of muscle contractions, moving the feed down. It has a bidirectional function, meaning it can move feed from the mouth to the stomach or from the stomach to the mouth.
Once the cow is finished chewing the cud, it again swallows the matter back down to the stomach. Generally, the stomach functions to further break down plant matter and grain.
More specifically, there are four sections of the stomach — rumen, reticulum, omasum and abomasum — each with a particular job to do. These sections store chewed plant material and grain, absorb nutrients and vitamins, break down proteins, aid in beginning digestion and dissolve material into processable pieces.
The next section will focus more closely on the responsibilities and functions of each stomach compartment. The small intestine has three main sections — the duodenum, jejunum and ileum — that work together to complete most of the actual digestive process. In the duodenum, the section connected to the stomach, secretions from the gallbladder and pancreas mix with the partially digested matter.
This process balances the pH in the intestine, ensuring the digestive enzymes work correctly. The jejunum section is lined with small, finger-like projections known as villi, which increase the intestinal surface area and absorb nutrients. The ileum absorbs vitamin B12, bile salts and any nutrients that passed through the jejunum. At the end of the ileum is a valve, preventing any backward flow of materials. Throughout the small intestine, muscular contractions move the matter forward.
In a fully mature cow, the entire organ may be up to feet long and has a gallon capacity. Sitting between the small and large intestines is a three-foot-long pouch called the cecum. It has little function besides providing storage and a transition between the two intestines, but it does aid in the continual breaking down of material. The cecum has about a two-gallon holding capacity. Smaller in length but larger in diameter than the small intestine, the large intestine is the final step of the digestive process.
It absorbs remaining water and contains bacteria microbes that finish digestion and produce vitamins the animal needs to grow and remain healthy. Its last job is to eliminate any undigested and unabsorbed food from the system in the form of waste.
When the cow is properly handled and fed, this process continually occurs, keeping the animal healthy and at the right weight. The entire digestion process should take anywhere from one to three days. If something interrupts this process or the cattle is unhealthy, the sections will no longer be able to function as well as they should, causing diseases and complications.
These compartments are:. This compartment acts as storage for chewed vegetation and forms balls of cud. Cud consists of large, non-digestible pieces of plant matter that must be regurgitated, chewed a second time and swallowed before continuing through the process. The rumen absorbs nutrients through papillae of the rumen wall and facilitates fermentation, creating the rumen bacteria and rumen microbes necessary to break down and digest the proteins in feed. Microorganisms in the rumen are responsible for digesting cellulose and complex starches, as well as synthesizing protein, B vitamins and vitamin K.
As a storage area, it can hold up to 40 gallons of material. While it does have its independent functionality, the reticulum is attached to the rumen with only a thin tissue divider. This component holds heavy or dense objects — such as metal pieces and rocks — and trap large feed particles that are not small enough to be digested. The reticulum facilitates regurgitation.
Both the rumen and reticulum contain digestive bacteria, so no acid is included in the regurgitation of materials. The reticulum holds about 5 gallons of material. One common health issue involving the reticulum is hardware disease, which occurs when cattle ingest heavy or sharp objects — like nails, screws or wire. They are swept into the reticulum and may puncture the stomach wall. This disease is preventable by putting magnets on feeding equipment to catch any metal, or cured by the placement of an intraruminal magnet that traps already swallowed objects.
It is lined with large leaves and folds of tissue that resemble the pages of a book. These folds absorb water and nutrients from feed that passes through after its second round of chewing.
It can hold up to about 15 gallons of material. This true stomach is the only compartment of the stomach lined with glands. These glands release hydrochloric acid and digestive enzymes to help the abomasum further break down feed and plant material.
Each of these components is vital in maintaining a healthy digestive process. Work with a veterinarian if this problem continues. Rumen microbes digest simple and complex carbohydrates fiber and convert them into VFAs. High forage diets result in more acetic acid forming 60 to 70 percent of total than propionic 15 to 20 percent and butyric acids 5 to 15 percent. More grain or finely ground forages can cause the amount of acetic acid to decline to 40 percent, while the amount of propionic acid may increase to 40 percent.
Microbes digest about 30 to 50 percent of the fiber units, cellulose and hemicellulose, in the rumen. Sixty percent or more of the starch is degraded depending on the amount fed and how fast ingested materials move through the rumen.
Most sugars get completely digested within the rumen. VFAs absorb into the bloodstream from the rumen and move to the body tissues including the udder. Once in the tissues, the cow uses VFAs as a source of energy for. Not all consumed proteins get broken down in the rumen, see figure 2. Through fermentation, protein is converted to ammonia, organic acids, amino acids and other products. About 40 to 75 percent of the natural protein in feed gets broken down.
Aside from protein breakdown, nonprotein nitrogen NPN sources also provide ammonia. NPN sources include urea, ammonium salts, nitrates and other compounds. Many rumen microbes need ammonia to grow and build protein. Rumen microbes convert ammonia and organic acids into amino acids to use for building protein. Most of the extra ammonia absorbs into the bloodstream from the rumen. But small amounts may pass into the lower digestive tract and absorb there.
Feed protein not broken down in the rumen and microbial protein pass to the abomasum and small intestine for digestion and absorption.
Rumen microbes make vitamin K and all B vitamins. Microbes make enough of these vitamins for cattle growth and maintenance.
Cows under stress may need added niacin B3 and thiamine B1. Most fat digestion and absorption occurs in the small intestine. Cows absorb more saturated fat than simple-stomach animals. This is because rumen microbes change unsaturated fatty acids to saturated fatty acids by adding hydrogen molecules. Feeding a lot of unsaturated fatty acids can be toxic to rumen bacteria, slow fiber digestion, and lower rumen pH.
The rumen, reticulum and omasum remain undeveloped at birth and during the first few weeks of life. During nursing or bucket feeding milk bypasses the rumen and directly enters the abomasum via the esophageal groove. Reflex action e. This prevents milk or milk replacer from entering the rumen. If the calf drinks milk rapidly, some may overflow into the rumen. The rumen will remain undeveloped as long as the calf stays on milk.
Once the calf begins eating grain and forage, a microbial population will develop in the rumen and reticulum. The end products from microbial fermentation are responsible for developing the rumen. Feeding grain with or without forage during the first few weeks of life will result in larger and heavier papillae growth in the rumen. All rights reserved. The University of Minnesota is an equal opportunity educator and employer.
Home Animals and livestock Dairy Dairy milking cows The ruminant digestive system. Quick facts Ruminant stomachs have four compartments: the rumen, the reticulum, the omasum and the abomasum. High grain to roughage ratios, some feed processing techniques and certain feed additives promote propionate at the expense of acetate.
The time required for food passage through the digestive tract ranges from 1 to 3 days depending upon characteristics of the food and the specific nutritient involved. In the mouth, chewing breaks the food into smaller particles. Digestive enzymes in saliva are mixed with food before it passes down the esophagus into the reticulo-rumen Figure 1. Although most of the feed undergoes fermentation, small amounts may pass unchanged through the rumen into the omasum and abomausm.
Some of the larger food particles will be regurgitated, chewed again and reswallowed. Protein in the diet is subjected to degradation partial or extensive by ruminal microorganisms Figure 2. Microbes degrade plant proteins to various degrees and use the resulting ammonia in the synthesis of microbial protein.
The extent of protein degradation varies with the type and solubility of the protein. This degradation and resynthesis process has advantages and disadvantages. Some high quality proteins may be degraded, thus reducing the quantity of essential amino acids available to the animal.
Heat and acid treatment to reduce protein solubility are currently being studied as methods of preventing degradation, thus saving the amino acids for use by the animal. On the other hand, extremely low quality plant proteins may be upgraded during digestions to a higher quality microbial protein. Plant proteins not degraded in the rumen along with microbial protein are passed to the lower tract. Digestive enzymes secreted in the abomasum break both plant and microbial protein into their component amino acids which are absorbed from the small intestines.
Non-Protein Nitrogen can be used as a substitute for plant nitrogen. Rumen microbes can use the non-protein nitrogen. Rumen microbes can use the non-protein nitrogen in the synthesis of microbial protein. Carbohydrates in the diet also are degraded by rumen microorganisms Figure 3.
Volatile fatty acids and gases methane and carbon dioxide are the end products of this process. Volatile fatty acids produced by rumen microbes are absorbed directly form the rumen. Gases are eliminated through eructation. Fiber , a complex carbohydrate, is composed of lignin, cellulose and hemicellulose. Lignin is very resistant to microbial attack, therefore little of it is digested. Cellulose is more readily digested than lignin, and hemicellulose is the most digestible of the three.
Starches and sugars also are readily converted to acids and gases. Unfermented feed residues and microbial cells are left to pass through the omasum to the abomasum. In the abomasum, the secretion of digestive enzymes prepares the foodstuffs for absorption in the small intestine. Some hydrogenation addition of hydrogen of unsaturated acids takes place in the rumen Figure 4. Unsaturated dietary fat soft fat subjected to microbial action in the rumen is transformed to a hard or a saturated fat.
Most fats are passed to the abomasum and small intestine where absorption occurs. Forage Utilization Forage and roughage account for a large quantity of the total world feed resources. Rumen microorganisms, through the production of enzymes, allow the ruminant animal to use the fiberous portion of these roughages as an energy source.
Non-protein Nitrogen Utilization Rumen microorganisms can manufacture protein form non-protein nitrogen. This microbial protein is later digested and supplies the animal with needed amino acids. Nonruminants must obtain essential amino acids directly form their diets. Vitamin Synthesis Rumen microorganisms can sythesize the B-complex vitamins and vitamin K.
0コメント