Digestive Systems
Digestive Systems ANATOMY, PHYSIOLOGY & ABSORPTION OF NUTRIENTS ANIMAL SCIENCE I Objectives* Name, locate and describe the functions of the parts of the digestive systems of ruminant and nonruminant animals Classify farm animals as ruminant and nonruminant Explain the relationship of types of digestive systems to the ability of ruminants and nonruminants to digest and absorb different classes of feed Defining the Digestive Systems Digestion-the process of breaking feed down into simple substances that can be absorbed by the body Absorption-taking the digested parts of feed into the bloodstream Digestive System (tract)-consists of parts of the body involved in chewing and digesting feed, absorbing nutrients and moving digested feed through the body Parts of the Digestive System* Mouth Esophagus Small Intestine Large intestine Rectum Anus Accessory organs Teeth, tongue, salivary glands, liver, pancreas Poultry Digestive System No teeth Crop and gizzard Ceca Cloaca Vent Digestive Capacities Vary among species Species, age, breed and size affect capacity Table 5-3 Ruminants are generally larger than nonruminants Ruminants Animals that have a stomach that is divided into several parts Cattle, sheep, goats, llamas, bison, deer Can digest large quantities roughage This is due to the bacteria present in their digestive system. Bacteria produce proteins, B-complex vitamins and vitamin K Nonruminants Animals that have simple, one compartment stomachs Swine, horses, poultry Require high energy, low fiber rations called concentrates Ruminant vs. Nonruminant usage of roughage Cattle and sheep 44% compared to swine 22% Horses fall in the middle at about 39% The Ruminant Stomach Parts Rumen Reticulum Omasum Abomasums Rumen Contain millions of protozoa and bacteria Muscles help break the food down into smaller particles so it is easier for bacteria to act No division between it and the Reticulum Reticulum Hardware stomach Foreign objects such as wire and nails go here and are held Thick walls Omasum 8% of stomach Strong muscles that grind up feed and squeeze out some water but how much is not know Somewhat of a mystery area Abomasum “true” stomach 7% stomach Feed is mixed with gastric juices Digestion is carried out here just like nonruminants How Ruminants Digest Eat rapidly Do not chew much of their feed before swallowing Solid part of the feed goes to the rumen; liquid part goes into the reticulum then the omasum and on into the abomasum In the rumen feed is partially broken down and mixed by bacteria. A slow churning and mixing takes place When full the animal lies down and feed is forced back into the mouth and rumination occurs. Cattle chew their cud 6-8 times per day Development of the Ruminant Stomach* Abomasums is the only part that functions Young ruminants can not use roughages Milk goes directly the abomasums When born the rumen is small and found in the upper left part of the abdomen After 2 months of age the rumen moves to its normal position The reticulum and omasum grow and develop rapidly By 3 months of age the rumen has grown enough to begin to function Digestion in Poultry Possess certain special digestive organs not found in other animals Crop Feed is stored and softened by saliva and secretions from the crop wall Muscular stomach Lined with a thick, horny membrane like material called epithelium Feed particles are crushed and mixed with digestive juices by the gizzard Ceca Two blind pouches where the small and large intestine join About 7” long Function is unknown but usually filled with soft, undigested food Cloaca Enlarged part where the large intestine joins the vent Vent Area of passage from the body for Feces from the large intestine Eggs from the oviduct Urine from the kidneys Absorption of Feed X Most takes place in the small intestine Villi-small finger shaped projections are key to absorption because they increase the surface area of the intestine As substances are absorbed by the blood capillaries in the villi, they pass through the liver and then the blood Water and dissolved minerals are also absorbed in the small intestine Digested Protein Absorbed in the form of amino acids Some sodium must be present for absorption to properly occur Digested Carbohydrates (Starches & Sugars) Present as monosaccharide's Glucose Fructose Galactose Fiber In the form of short-chained fatty acids Adenosine triphosphate (ATP) supplies the energy for the absorption of the monosaccharide's and fatty acids Sodium must also be present Digested Fats (soaps and glycerol) Form into fats again and are absorbed by the lymph vessel in the villi. They pass through the thoracic duct in the neck and into the circulatory system Absorption in the Large Intestine Water and some nutrients are directly absorbed into the bloodstream through capillaries in the intestinal wall This is especially important in horses because much of the microbial digestion of roughage occurs in the cecum End of the Nutrients Journey Most in the muscle cells Some are deposited in the liver Used to replace worn out cells and build new for energy or stored as fat for later use Metabolism Sum of the processes, both chemical and physical that are used by living organisms and cells to handle nutrients after they have been absorbed from the digestive system Process Anabolism—formation and repair of body tissue Catabolism—breakdown of body tissues into simpler substances and waste Oxidation of nutrients provides energy Summary Ruminants can use a lot of roughage They have a 4 part stomach in which bacteria breakdown the roughages Nonruminants must have more concentrates such as grain, in their ration because they have simple one part stomachs Most digested feed is absorbed in the small intestine of the animal Small intestine has millions of tiny villi Assignment Discussion 24, 25, 27, 29-33, 35, 37 Review Questions 1-11 Due Friday Aug 31 end of period.
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