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Digestion the process of breaking feed down into simple substances that can be absorbed by the body. 3 metabolic processes that contribute to this break down: anabolism catabolism oxidation Anabolism: is the set of metabolic pathways that construct molecules from smaller units. These reactions require energy Anabolism is powered by catabolism Examples: "building up" organs and tissues. anabolic processes include the growth and mineralization of bone and increases in muscle mass. Catabolism: the breakdown of body tissue into simpler substances and waste production Oxidation: what happens to nutrients that provide energy for the animal Absorption: refers to taking the digested parts of the feed into the bloodstream movement of nutrients across the lining of the intestinal tract into blood and lymph system. Metabolism: the chemical reactions in cells The appetite of the animal is controlled by the hypothalamus gland Functions of the digestive system of animals: 1. Ingestion (eating) 2.grinding 3.digestion 4.absorption of nutrients 5. elimination of waste Mechanical Activities of the Stomach: mastication (chewing) deglution (swallowing regurgitation (throwing up) gastric and intestinal motility (peristalsis) defecation (eliminate waste) Chemical Activities of the Stomach: Actions of enzymes and other substances produced and secreted by digestive glands Microbial Activities of the Stomach: 1. activites of bacteria and protozoa (especially in the use of roughages) 2. substances produced and secreted by digestive glands Ruminants: stomach is divided into four parts 1 2 3 4 rumen reticulum omasum abomasum Examples: cows, deer Ruminants are cud-chewing animals. They can digest large quantities of roughages (such as hay and pasture) Non-ruminants: have simple, onecompartment stomachs. Examples: pig, horses, poultry, humans They need high-energy, low-fiber rations such as grain Grains and protein supplements are called concentrates. *most expensive part of a ration high fiber feeds such as hay, silage, and pasture 44 percent of the roughages cattle and sheep eat, they actually digest. 39 percent are digested by horses. 22percent are digested by swine Ruminants can digest large quantities of roughage because of the bacteria present in their digestive system. Mouth: start of digestive tract saliva contains enzymes, salivary amylase, salivary maltase Horses saliva doesn’t contain enzymes. Saliva moistens the feed for chewing and swallowing mucin lubricates the feed for swallowing prostaglandin secretions and bicarbonate buffer the pH in the stomach Enzymes: organic catalysts that cause and or speed up digestive action Teeth: Incisors: Cutting or shearing food Premolars and molars: Grinding food Ruminants: no upper teeth and a hard upper dental pad Hard palate: roof of the mouth -Turns to soft palate toward the rear of the mouth Salivary glands: -Common in mucous membrane lining of the mouth, except on the tongue, hard palate, and gums Tongue: Mass of muscle covered by a mucous membrane Covered with finger-like projects called papillae Contain taste buds Cheeks: Are made mostly of muscle lined with a mucous membrane and line food up with teeth Pharynx Common passage for food and air Several structures open to the pharynx: mouth nasal cavity Eustachian tubes from the ears larynx esophagus Non ruminants have two striated muscles that control the passage of food in and out of the stomach Esophageal Groove: Extends from the initial opening of the stomach to the omasum Causes food to bypass to the rumen and reticulum Cardia: Sphincter muscle located at the junction of esophagus and stomach Pylorus is another sphincter muscle located at the bottom of the stomach These control the passage of food in and out of the stomach Rumen 80% of the stomach food goes from the esophagus to this part of the stomach first -AKA - fermentation vat Digestion in the Ruminant: Rumen provides favorable environment for microbial growth due to: a. b. c. d. e. f. Buffered pH Temperature maintained at 101 to 103 degrees Primarily a liquid media Food supply replenished daily End products of digestion removed Anaerobic Rumen Feed Storage: Gas Today’s Hay Yesterday’s Feed Microbes use ammonia and amino acids, energy, and minerals for growth cheap type of ammonia = urea Papillae (tripas): finger like lining of the rumen. honeycomb lining of the reticulum Reticulum food goes back and forth from the Rumen to Reticulum to break down to particle size Considered the “honeycomb” Site of Hardware Disease Helps move and regurgitate digesta Collects objects that shouldn’t be in the digestive system. Nails Screws Baling wire Reticulum (Hardware Stomach or Tripe) Function – Site of microbial action & absorption of Volatile Fatty Acids • Pacemaker for rumen contractions a. b. c. d. Contractions start in reticulum spread to rumen Mixes rumen contents Heavy particles move to bottom, lighter ones float Lighter particles subject to rumination (Rumination = regurgitation, remastication, resalivation, reglutition) Omasum: Increases size but may squeeze some water out of the feed (H2O absorbed here) Acts like a filter, holds back feed stuff that hasn’t been broken into smaller particles Regulates particle size flowing to abomasum/S.I. “many piles”, lamina propia -has a lot of leaves and folds called papillae -Function is unclear -Some mechanical digestion from lamina Omasum (manyplies) Abomasum (true stomach) everything done like a non-ruminant’s stomach Secretes digestive juices. Breaks down food stuff further for absorption. Absorbs some nutrients. Abomasum Eructation: Belching of gas Improper eructation leads to bloat Gallbladder: Horses don’t have one It empties waste as bile through the common bile duct into the duodenum Pancreas: produces the hormone insulin which deposited into the bloodstream located in the first loop of the duodenum Liver worn out red blood cells are destroyed here has a duct that merges with the pancreas and empties into the small intestines Bile yellowish-green, alkaline, bitter liquid aids in the digestion of glycerol and fatty acids Hydrochloric Acid Aids in the dissolving of minerals in diet Small Intestines: work to break down solids The end product of digestion of protein are amino acids Go through the blood stream to cells. Villi: Finger-like projections line small intestine Primary site of absorption of nutrients Duodenum: first part of the small intestines secretions from the pancreas, liver, and intestinal walls occur here is secreted here. Jejunum middle part of the small intestines nutrient absorption occurs here Ileum last part of the small intestines nutrient absorption occurs here Layers in the intestine Large intestines: Vitamins E and K are synthesized in the large intestine. These are fat soluble vitamins. Bacteria in the LI produce some amino acids, but mostly fatty acids Fatty acids = energy Amino acids = protein synthesis Large Intestine: Divided into: 1 cecum 2 blind pouch 3 colon 4 ends in the rectum and anus Cecum: first part of the large intestine ruminants have bacteria here which allows it to use large amounts of roughages primary water absorption site. Fermentation occurs in the cecum, similar to the action that takes place in the fore-stomach of the ruminant colon middle and largest part of the large intestine Rectum Connects the small colon with the anus. Receives feces from the small colon, which formed the characteristic balls of horse manure. Reabsorbs water that was not absorbed in the cecum.