Session 1 intro and digestive systems 2018(1)
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This document provides an overview of animal nutrition and digestive systems. It begins by outlining the course objectives and requirements for a veterinary nutrition course. It then discusses the different types of digestive systems, including monogastric systems like dogs and cats, and ruminant systems like cows. Key aspects of each system are described, such as the structure and function of different stomach compartments. The roles of saliva, stomach secretions, and pancreatic enzymes in chemical digestion are also summarized. Finally, the chronology of digestion from ingestion to absorption in the small intestine is outlined.
Session 1 intro and digestive systems 2018(1)
- 1. VTS 150 Animal Nutrition Spring 2018 Beth Alden, DVM Instructor
- 2. Course Objectives Identify the components of the digestive systems of common companion animals Identify the nutritional needs of common companion animals Correctly calculate the caloric needs of companion animals Correctly evaluate a pet food label and ingredients Identify common toxins for companion animals
- 3. Resources for Class Textbook: Nutrition and Disease Management for Veterinary Technicians and Nurses Ann Wortinger/Kara Burns
- 4. Case Studies in Veterinary Technology; by Rockett & Christensen (required text)
- 5. Resources on Library Reserve Small Animal Clinical Nutrition 4th Edition, Hand,Thatcher, Remillard, Roudebush, The Mark Morris Institute, 2000
- 6. Student’s Requirements Exams Discussions Toxin project Case studies Final project
- 8. Digestive System Connects animals diet with metabolic needs A muscular tube from mouth to anus grinding, mixing, moving and absorbing nutrients Glands manufacture secretions that are added to the tube to assist in digestion Ruminants harbor bacteria in the digestive tract that assist in digestion and synthesis of essential nutrients All animals have microbes in the digestive tract that assist in digestion, veterinarians are harnessing their power as nutricueticals ( beneficial bacteria administered to animals)
- 9. Diet and digestive tract Herbivores – plant eaters Carnivores- meat eaters Ominivores- plant and meat eaters Insectivores – insect eaters Frugivore – fruit eaters (many species eat fruit as part of their diets, these animals eat only fruit like some bats)
- 10. Digestive tracts The anatomy of the digestive tract is designed for the type of food the animal utilizes Carnivores have short digestive tracts that hold a small volume of food Herbivores have large digestive tracts that hold a large volume Insectivores and frugivores have digestive tracts that are designed for that diet
- 11. Herbivores Vegetation, nitrogen source, minerals and water Difficult to digest, large complex gut is needed - Plant cell walls are hard to break down - Cellulose is the storage form of the plants glucose - Microbes in the gut break down the cellulose and utilize the glucose to make their energy and volatile fatty acids (butyric, propionic and acetic acid) - The animal utilizes these volatile fatty acids - Very little of the food’s energy is actually absorbed
- 12. Carnivores Animal material (flesh, muscle, viscera) makes up the diet More easily digested than herbivore diet GI tract is basically a simple tube Most of the food energy is utilized and absorbed Mechanical breakdown of food is less involved
- 13. Digestive system types Monogastric - One “true” stomach like dogs, cats, pigs, horses (horses are non- ruminant herbivores) Ruminant - Four compartment stomach - Rumen, reticulum, omasum, abomasum - Cows, sheep, goats
- 14. Types of Digestive Systems
- 15. Monogastric Stomach Five sections - Cardia - Fundus - Body - Antrum - Pylorus
- 16. The Monogastric Stomach 1. Cardia Area immediately surrounding the opening from the esophagus into the stomach Muscular tone prevents reflux of stomach contents into the esophagus Source: University of California at Davis CARDIA
- 17. The Monogastric Stomach 2. Fundus Located below the cardia Blind pouch that distends as food is swallowed Source: University of California at Davis FUNDUS CARDIA
- 19. The Monogastric Stomach 4. Antrum Grinds up food and regulates HCl Also contains glands BODY Source: University of California at Davis FUNDUS CARDIA BODY ANTRUM G Cells: Gastrin Mucous Cells: Mucus
- 20. The Monogastric Stomach 5. Pylorus Muscular ring (sphincter) Regulates movement of chyme from stomach into duodenum Helps prevent backflow of duodenal contents BODY Source: University of California at Davis FUNDUS CARDIA BODY ANTRUM PYLORUS DUODENUM
- 21. Ruminant Animals
- 22. Ruminant Chews food briefly and swallows Regurgitates “cud” to chew again and swallow (vital to help break down cellulose) The stomach is designed to allow this regurgitation and swallowing, plus the action of microbes on the diet (four compartment stomach)
- 23. The Ruminant Stomach Four Compartments: Reticulum Rumen Omasum Abomasum Source: University of California at Davis head tail
- 24. Source: University of California at Davis head The Ruminant Stomach 1. The Reticulum Smallest, most cranial compartment Separated from rumen by the ruminoreticular fold Muscular wall is continuous with the rumen; contract in coordination tail RETICULUM
- 25. The Ruminant Stomach Reticulum ( continued) Honeycombed inside to increase absorptive surface “Hardware disease”- wires or nails swallowed by animal puncture wall of reticulum Inside of Reticulum Source: Colorado State University RETICULUM
- 26. The Ruminant Stomach 2. The Rumen Large fermentative vat (40 - 50 gallon capacity) Processes plant material into usable energy Lined with “Papillae” Made up of series of muscular “Pillars” Source: University of California at Davis head tail RUMEN
- 27. Close up view of rumen © University of Bristol, 1988 Pillar PapillaePapillae
- 28. Working of the Rumen During contractions, pillars close off certain sacs of the rumen which allows mixing of ruminal contents Mixing of contents essential for fermentative function of rumen RUMEN
- 29. During contractions, pillars close off certain sacs of the rumen which allows mixing of ruminal contents Mixing of contents is essential for fermentation in the rumen Fermentation breaks down the nutrients for the microbes and the animal and produces vitamins B and K Carbon dioxide and methane are the byproducts of this process
- 30. Reticuloruminal Contractions Allow “cud” to be regurgitated into the esophagus and into the mouth where it is re-chewed and re-swallowed (helps break down this difficult to digest diet) Allows “eructation” of built up carbon dioxide and methane gas in the rumen. Gasses are forced into the reticulum and up the esophagus Interference with eructation leads to bloat which can be deadly
- 31. Fermentative digestion Begins in the rumen Bacterial, protozoal and a small amount of fungi utilize their enzymes to begin breaking down food The microbes utilize the energy in the diet to grow and reproduce
- 32. Carbohydrate Metabolism Cellulase enzymes digest cellulose and transform the complex carbohydrate into simple sugars These simple sugars are not available to the host animal (like they are in monogastric animals) instead they are absorbed and utilized by the microbes which produce Volatile Fatty Acids (VFA’s) The host animal utilizes the volatile fatty acids
- 33. Carbohydrate Metabolism Continued Volatile fatty acids are the byproducts of anaerobic fermentation by microbes in rumen Anaerobic fermentation means it does not utilize oxygen Some of the VFA’s are utilized by the ruminant to produce glucose Other VFA’s are used to produce adipose tissue and milk fat
- 34. Protein Metabolism Rumen microbes digest proteins just like carbohydrates Proteases (enzymes) reduce long proteins to amino acids (the building blocks of proteins) and short chain peptides (short chains of amino acids) Peptides are either incorporated into the protein structure of the microbes OR converted to ammonia (NH3+) and VFA’s
- 35. Protein Metabolism Continued Liver secretes urea into the rumen, this provides the rumen microbes with additional nitrogen (the rest of the nitrogen they get from digesting the proteins in the diet) Microbes get flushed from the reticolorumen to the omasum, abomasum and intestines where they serve as an additional protein source for the host animal Urea is sometimes added to poor quality feeds to meet the nitrogen needs of the animal
- 36. Other rumen notes Microbes provide B vitamins, and vitamin K The rumen environment is a delicate balance of food, microbial growth and by-products Abrupt changes in diet severely affect the production of methane, CO2, VFA’s and ammonia causing fermentation and changes in rumen ph
- 37. 3. Omasum Muscular organ located off the reticulum Ingesta moves into omasum from reticulum and rumen Prevents large particles from leaving rumen and entering abomasum OMASUM Source: University of California at Davis head tail
- 38. Omasum Primary Functions Break down food particle further and move them into the abomasum Absorb any excess VFA’s Remove bicarbonate ions from ingesta (to avoid altering acid ph of abomasum) Bicarbonate ions come from the saliva (ruminants produce a huge amount of saliva which goes into the rumen to help buffer ph) If saliva flow is blocked by a foreign object or lack of production, the animal can become severely acidotic (remember VFA are ACIDS)
- 39. The true stomach 4. Abomasum “True stomach” of ruminant Functions similar to monogastric stomach ABOMASUM Source: University of California at Davis head tail
- 40. Young Ruminant Digestive Tract Functions as a monogastric stomach No fermentative digestion (rumen and reticulum are non functional) Reticular groove or esophageal groove forms when suckling and allows milk to go directly to omasum Bucket fed calves don’t form this groove and milk spills into the rumen and reticulum
- 41. Young Ruminant Continued Abomasum is largest of 4 stomachs for the first few weeks of life Rumen and reticulum development rate depends on diet - grain and hay fed- develops at 3 weeks - milk fed develops at 3 months Veal calves are fed milk for their entire short lives to produce a very tender soft meat
- 42. Digestive System Chronology GI tract extends from mouth to the anus and performs different functions at different sections 1. Prehension 2. Mechanical grinding down of food 3. Chemical digestion of food 4. Absorption of nutrients and water 5. Elimination of waste material
- 43. Prehension Grasping with teeth or lips Cows do not have upper incisors, they have a toothless area called a dental pad Cows use the bottom incisors and dental pad to bite grass Dogs, cats have sharp tearing teeth to rip flesh
- 44. Mechanical Grinding Down of Food Carnivores have pointed teeth to facilitate holding and tearing of food Herbivores have flat surface molars that grind from side to side to break down plant material (watch a rabbit chew, horses, cattle chew the same way) horses form sharp edges (points) on their molars that have to be filed down from time to time (floating the teeth)
- 45. Chronology of Digestion: Mechanical Grinding Down of Food Carnivore Teeth Pointed to facilitate holding and tearing of food © Clinical Textbook for Veterinary Technicians 6th ed.; McCurnin, Bassert
- 46. Chronology of Digestion: Mechanical Grinding Down of Food Incisors – Teeth in the front for holding and tearing Canines – Pointed teeth located at corners for tearing and shredding Premolars – Located just before the molars and are used for grinding in all species Molars – Used for grinding
- 47. Chronology of Digestion: Mechanical Grinding Down of Food Herbivore Teeth Flat, occlusal surface for grinding
- 48. Ruminant Teeth No upper incisors or upper canine teeth Chronology of Digestion: Mechanical Grinding Down of Food Dental Pad Thick connective tissue Diastema
- 49. Teeth Terminology Maxilla – upper jaw Mandible- lower jaw Lingual- inner side of lower arcade of teeth that face the tongue Labial- outer surface of upper and lower arcade teeth that face the lips Palatal- inner side of upper arcade teeth that face the palate Buccal- outer side of teeth on sides of mouth that face the cheeks
- 50. Canine Dental Formula Triadan
- 52. Chemical digestion of food Saliva mixes with food during chewing Three pairs of salivary glands located bilaterally (one on each side) Parotid (2), mandibular(2), lingual (2) salivary glands Saliva 1. moistens, softens, shapes and lubricates food 2. Aids in taste, acts as a buffer 3. Provides digestive enzymes
- 53. Chemical Digestion of food Continued Digestive enzymes and buffers in saliva 1. amylase- in omnivore saliva, not present in carnivores, breaks down amylase a sugar component of starch 2. Lipase- breaks down lipids 3. Bicarbonate and phosphate buffers- in cow saliva, neutralizes acids in rumen and maintain normal rumen ph ( up to 25-30 gallons of saliva a day)
- 54. Chemical Digestion of Food Continued Food moves from mouth to pharynx where the epiglottis prevents food from entering the trachea Food is transported into the esophagus Esophagus utilizes peristalsis, rhythmic contractions to propel food to the stomach
- 55. From the esophagus In ruminant 1. from esophagus to reticulum 2. reticulum to rumen 3. food from rumen and reticulum regurgitated for rechewing and swallowing 4. Reticulum and rumen to omasum 5. Omasum to abomasum
- 56. From the esophagus in non ruminant Food goes directly into the stomach Dogs, cats, horses, rabbits rats etc
- 57. Chemical Digestion of Food Stomach (non ruminant) Abomasum ( ruminant) 1. Stores food 2. Continues enzymatic breakdown of food (pepsin, gastrin, mucus, hydrochloric acid all playa role) 3. Mechanical breakdown of food, mixing, grinding, contractions that move food 4. Ruminants: rumen, reticulum, omasum lead to abomasum ( the true stomach)
- 58. Chemical Digestion Continued Liver- secretes bile acids to help with digestion of fats, keeps the fats in solution Pancreas- secretes enzymes into small intestine for breaking down nutrient 1. Protease for proteins 2. Amylase for carbohydrates 3. Lipase for fats/lipids 4. Bicarbonate to neutralize stomach acid
- 59. Absorption of nutrients and water Small intestine consists of three parts, duodenum, jejunum and ileum Continues peristalsis Villi and microvilli increase surface area for absorption No clear demarcation between three segments All 3 segments perform peristalsis, absorb nutrients and water
- 60. Small Intestine Duodenum- first portion of the small intestine receives contents of stomach Jejunum- majority of small intestine Ileum- where small intestine enters the colon ( the cecum is located at this junction) Cecum is very small in carnivores and large in herbivores like horses ( in horses cecum bacteria digest herbivore diet)
- 61. Villi Villi- - millions of cylindrical fingerlike projections from the intestinal wall - Provide large surface area for absorbing nutrients - Crypts surround villi and replenish the cells that cover the villi
- 62. Microvilli Microvilli - Brush border, extensions of the surface of the cells that cover the villi - Increase the surface area of the cells and the absorptive capacity - Contain digestive enzymes - Clinical example TGE transmissible gastroenteritis in pigs and parvovirus in dogs attack and destroy the villi preventing absorption of nutrients from the intestinal tract
- 63. Functions of Small Intestine Small intestine absorbs electrolytes (Na, Cl, K, etc) water, and vitamins Absorbs carbohydrates, fats, proteins after chemical digestion via enzymes
- 64. Nutrient Digestion in the Small Intestine Carbohydrates- digested by amylase secreted from the pancreas Proteins- digested by proteases secreted by the pancreas Fats- digested by bile acids from liver which helps emulsify fat (emulsify means to keep in solution), further broken down by lipase secreted from pancreas
- 65. Elimination of Waste Material Large intestine: cecum and colon - Recover fluid and electrolytes - Store feces until elimination - Some microbial action - Differences between species dependent on diet
- 66. Elimination of Waste Material Carnivores - colon – simple, tubular, contracts to move feces through - Cecum “ blind sac” poorly developed Herbivores - Colon – large bacterial population of microbes for fermentation - Cecum “blind sac” more developed, larger than carnivore for digestion of herbivore diet
- 67. Colon Colon in carnivore is much smaller than in herbivores Responsible for reabsorbing water and electrolytes
- 68. Elimination of Waste in Herbivores Such as Horses Colon and cecum comprise the “Hindgut” 4 sections, cecum, ventral colon, dorsal colon, small colon More highly developed than small intestine Has greater capacity for fermentation ( acts similar to microbial digestion in rumen) Unique digestion path – colonic impaction is most common form of colic in horses
- 69. Rectum and Anus Rectum - Terminal portion of colon - Contains mucus secreting glands - Sensory receptors detect stretching/distension and triggers defecation Anus - Internal and external sphincters allow controlled passage of feces
- 70. Birds Esophagus leads to the crop where food is stored Moves into the proventriculus Then the gizzard ( mechanical stomach that acts as the birds teeth)chickens will eat small stones that end up in gizzard and will help with grinding. Eventually they break down and are passed in feces Chickens tend to eat small shiny objects like tacks, they will pierce the gizzard and can kill the bird
- 71. The small intestine of the chicken is made up of the duodenum and the lower small intestine Ingesta then goes into the ceca for further digestion Into the colon and out the cloaca ( the cloaca is a common opening for the fecal and urinary material) Bird do not have a bladder.
- 72. Next Week… Session 2: Basic Nutrients