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Digestion The process of breaking down feeds so the body can use them Four steps in digestion 1. Obtaining food and taking into the body 2. Breaking food down 3. Absorbing nutrients 4. Elimination of undigested wastes Obtaining Food Animals use their SENSES to find FOOD. Food is taken in through the MOUTH. This is called INGESTION. Amount of Food Ingested is determined by: Hunger -- the intrinsic desire for food, regardless of food type or preference Appetite -- the specific type of food that is preferentially sought. What Animals Eat Herbivore -- majority of diet comes from plant products Examples -- Cow, Sheep, Goat, Horse, Rabbit Carnivore -- majority of diet comes from animal products Examples -- Dog Omnivore -- eats both plant and animal products Examples -- Humans, Pigs, Poultry, Mouse Breaking Food Down Food is broken down in two ways: 1. CHEMICAL -- the use of chemical substances (ENZYMES) to dissolve the food. 2. MECHANICAL -- the use of PHYSICAL structures (chewing, grinding) to break the food apart. Food is broken down in the following structures: Mouth -- MASTICATION -- grinding or chewing of food SALIVA--watery liquid in mouth that begins dissolving the food. Mastication -- Teeth Incisors -- cutting and food intake action 55 psi Canines -- ripping and biting (Carnivores and Omnivores only) Premolars -- grinding action Molars -- grinding action 200 psi Esophagus the muscular tube connecting the MOUTH with the STOMACH PERISTALSIS -- the movement of food through the digestive system by a series of muscular contractions Analward Peristaltic Movements Stomach Compartment used for digestion and storage Cattle and sheep (RUMINANTS) have 4 compartments Horses and swine (NONRUMINANTS) have 1 compartment Absorbing Nutrients Nutrients leave the digestive tract and enter the blood so they can be used by every cell Small Intestine most of the food nutrients are absorbed into the blood here The small intestine is very LONG and contains many small folds called VILLI which increase the surface area for more absorption. Three parts Duodenum, Jejunum, Illeum Large Intestine Water is absorbed into the blood and undigested wastes prepare to leave the body Removal of Undigested Wastes Not all of the food eaten can be digested and absorbed. After most of the water is absorbed, waste is removed from the body through the anus or vent. Other organs that assist in digestion liver -- stores carbohydrates (glycogen), detoxifies blood, produces bile pancreas -- produces insulin and pancreatic juice gall bladder -- stores bile until it is needed Terminology of feed as it moves through the system Feed or Feedstuff Ingesta Cud Chyme Digestive End Products (DEP’s) Fecal Material or Non-Digested End Products Feces The GI tract -- Descending Oral cavity (mouth) Incisors Molars Esophagus Stomach 1 compartment, or 4 compartments Small Intestine Duodenum Jejunum Illeum Cecum Large Intestine Rectum Anus (Colon) Enzymes and Chemicals Name of Enzyme Amylase Type of food broken down What the food Becomes Starch (carbohydrates) Disaccarides (carbohydrates) Lipids (fats) Fatty acids Maltase Maltose (carbohydrates) Glucose Lactase Lactose (carbohydrates) glucose and galactose Pepsin Protein peptides Peptidase peptides amino acids Trypsin protein peptides Sucrase sucrose glucose and fructose Lipase Name of Chemical Gastric Juice Where Produced Enzymes Contained Lining of the stomach hydrochloric acid, pepsin Liver (stored in gall bladder) Lipase Pancreatic Juice Pancreas Lipase, trypsin, amylase Intestinal Juice Lining of the small intestine Sucrase, Maltase, Peptidase, Lactase Bile Ruminant Digestive System Cattle and sheep have a RUMINANT digestive system. This means that their stomachs have FOUR compartments. The first of these compartments contains many MICROORGANISMS that help break down CELLULOSE. Ruminant Digestive System Cellulose -- a substance found in the cell walls of plants. It cannot be used unless it is first broken down fermented) by microorganisms. Ruminant Digestive System Two types of Microorganisms Bacteria -- digest and ferment readily available carbohydrates; digest and ferment the cellulose and hemicellulose part of feed. Protozoa -- store readily available carbohydrates; produce protein; ferment cellulose material Ruminant Digestive System Regurgitation -- ruminants consume large amounts of roughage. It is first chewed just enough to swallow it. After they consume the food, they REGURGITATE it, or force it back into the mouth, so that it can be chewed again. (Chewing CUD). Ruminant Digestive System 4 parts of a ruminant stomach Rumen -- the largest compartment; stores and ferments the feed Reticulum -- foreign particles (nails, wire) are removed Omasum -- eliminates water from the feed Abomasum (true stomach) -- gastric juice is secreted;feed is broken down Ruminant Digestive System Monogastric Digestive System Monogastric Digestive System Swine, dogs, bears and humans have only one stomach. These animals cannot digest cellulose. Monogastric Digestive System Modified Monogastric System Modified Monogastric System Horses and rabbits have only one stomach, but have structures that contain microorganisms so they can digest cellulose. Microorganisms are found in the cecum and in the large intestine. Modified Monogastric System Avian Digestive System Birds (Turkeys, Chickens and pigeons) have structures not found in other species that allow them to digest shells of seeds and other hard foods. Avian Digestive System Crop -- a storage organ that holds food until it can be digested Gizzard -- grinds the food Cloaca -- the cavity just before the vent that collects undigested wastes, uric acid (instead of urine -- high in nitrogen), and reproductive cells. Avian Digestive System