Ruminant Digestive System PDF 2016

4A STOMACH AT WORK RESOURCE SHEET The Basics of the Ruminant Digestive System Digestion Introduction In general, livestock animals have one of two major types of digestive The process of breakin...

4A STOMACH AT WORK RESOURCE SHEET The Basics of the Ruminant Digestive System Digestion Introduction In general, livestock animals have one of two major types of digestive The process of breaking down food systems: monogastric or simple (see fig. 1) and ruminant or complex in the mouth, stomach, intestines and (see fig. 2). Monogastric animals include swine, horses, chickens and other organs so that it can be used by other poultry. Ruminant animals include cattle, sheep and goats. Table the body. 1 lists a few of the major differences between monogastric and rumi- nant digestive systems. Table 1. Major differences between monogastric and ruminant digestive systems Difference Monogastric Ruminant digestive digestive system system Number of stomach compartments 1 4 Number of times food is chewed Several Once times Efficiency in digesting plants and plant Highly Limited byproducts developed Ruminant animals chew their food several times through a process called “rumination” or “chewing the cud.” When a ruminant animal such as a cow takes a bite of grass or other food, the animal chews the food just enough so it can be swallowed. The food then travels from the mouth down the esophagus to the rumen (the first and largest stomach compartment). From there, it moves to the second compartment, the reticulum. Later, the cow can regurgitate the food Figure 1. A diagram of the monogastric (now called a “bolus” or “cud”) to chew it again to continue breaking digestive system of swine. (Courtesy of down the plant fibers. the Oklahoma Department of Career and Technology Education, Curriculum and The stomach compartments of a ruminant animal are much larger Instructional Materials Center) than the stomach of a monogastric animal because it takes ruminants longer to ferment, mix and digest the roughage they’ve eaten. They need plenty of room in their stomachs for all of that to happen. Figure 2. A diagram of the ruminant digestive system of cattle. (Courtesy of the Oklahoma Department of Career and Technology Education, Curriculum and Instructional Materials Center) 4-H Animal Science Anywhere | Michigan 4-H Youth Development | Michigan State University Extension Copyright 2016 Michigan State University Board of Trustees. Michigan State University is an affirmative action/equal opportunity employer. 7  4A STOMACH AT WORK RESOURCE SHEET Four Stomach Compartments The stomach of a ruminant animal has four compartments. In the order that food travels through them, they are the rumen, reticulum, omasum and abomasum. Each compartment has a distinct function and appearance. They’re described here. The Rumen The rumen (see fig. 3) is the largest compartment of the ruminant stomach – it can store up to 50 gallons of digested materials. Food Figure 3. A close-up of a rumen. (Photo: Dr. is fermented in the rumen, because the environment is anaerobic Karen E. Petersen, Department. of Biology, (has no oxygen). That allows for increased microbial action and high University of Washington.) concentrations of bacteria (“rumen bugs”). The rumen is capable of changing poor-quality protein (such as the nitrogen in grass) to a good-quality microbial protein. To aid in this process, the rumen is very selective about how quickly particles can move from one stom- ach compartment to another. If a roughage is difficult to digest, the rumen will extend fermentation time to allow for further mechanical breakdown through the process of cud chewing. The rumen has fin- gerlike projections called “papillae” that increase the surface area on which microorganisms do their work. When a cow eructates (belches), it’s releasing fermentation gas (mostly carbon dioxide and methane). Figure 4. A close-up of a reticulum. (Photo: The Reticulum (Honeycomb) Dr. Karen E. Petersen, Department. of Biology, The reticulum (see fig. 4) is attached to the rumen and consists University of Washington.) of bands of smooth muscle. The walls of the reticulum look like honeycombs, which give it the nickname “the honeycomb.” Its main functions are to first detect large feed particles that need to be broken down further, and second to regurgitate or force those particles back up the esophagus to the mouth so they can be chewed and then swallowed again. Cows have an unfortunate habit of accidentally ingesting hardware such as nails and bailing wire. These foreign objects usually wind up in the reticulum and sometimes have to be surgically removed. The Omasum Figure 5. A close-up of an omasum. (Photo: Many folds or layers of muscle (called “plies”) make up the omasum Dr. Karen E. Petersen, Department. of Biology, (see fig. 5). These folds increase the compartment’s surface area, University of Washington.) which helps it absorb nutrients from feed and water. The omasum squeezes water from the feed particles and continues to break them down into smaller particles. The Abomasum (True Stomach) The abomasum (see fig. 6) is called the “true stomach” because it’s the equivalent of the stomach of a monogastric animal. This is where acids and enzymes (digestive juices) mix with and prepare feed for enzyme breakdown and absorption in the small intestine. It has a very low (acidic) pH. This is the feed’s last stop before entering the small intestine where most nutrient absorption will take place. Figure 6. A close-up of an abomasum. (Photo: Dr. Karen E. Petersen, Department. of Biology, University of Washington.) 8 4-H Animal Science Anywhere | Michigan 4-H Youth Development | Michigan State University Extension Copyright 2016 Michigan State University Board of Trustees. Michigan State University is an affirmative action/equal opportunity employer.