Digestive System of Livestock and Poultry PDF

UNIT 10 THE DIGESTIVE SYSTEM  Function of the digestive system Organs of digestion in monogastric animals Organs of digestion in ruminants Avian digestive system Associated structures Physiologic processes Deve...

UNIT 10 THE DIGESTIVE SYSTEM  Function of the digestive system Organs of digestion in monogastric animals Organs of digestion in ruminants Avian digestive system Associated structures Physiologic processes Development aspect of digestion  Describe the organs that make up the digestive system of livestock and poultry Discuss the role and physiologic processes in the digestive system Differentiate the digestive systems of livestock and poultry species Correlate the functions of the digestive system with production practices and expectations  ANIMAL NUTRITION & DIGESTION NUTRITION is the study of the body’s need and mechanism for acquiring, digesting, transporting and metabolizing nutrients The purpose of nutrition is to provide animals with nutrients to enable them to optimize: health, feed efficiency and profits It deals with how animals: consume, digest, absorb, transport, metabolize and excrete the nutrients found in feed  Animal Nutrition further considers: how the nutrients are used in the body and then consider the economics of feeding for productive purposes, and the potential effects of various feeds, additives, medicinal, and so on to the human population GOOD NUTRITION IS BASIC TO GOOD HEALTH AND PRODUCTION  Of the total costs of various enterprises, the portions attributed to feed ranges from: 65-80% for swine, 55% for layers, 65% for broilers and turkeys, 50-60% for dairy cattle, 70% for feedlot finishing of beef cattle and 50% for feeding lambs  The digestive system is a PORTAL for nutrients to gain access to the circulatory system Food is broken down to very simple molecules such as sugars, amino acids, fatty acids, etc… that are then transported across the GI tract lining into blood Classification of Animals Based on Diet Carnivore Omnivore Herbivore Classification of Animals Based on Type of Stomach Monogastric or Non-ruminant – simple stomach; avian and psuedo ruminants Polygastric or Ruminant – compound stomach; cattle, buffalo, goat, sheep  THE ALIMENTARY TRACT/CANAL It extends from the lips, mouth, pharynx, esophagus, stomach, small intestine (Duodenum, jejunum and ileum), large intestine (Caecum, colon and rectum) and anus In carnivores, alimentary tract is small and simple The simple stomach herbivores (horse, rabbit), are also referred as HINDGUT DIGESTERS because they have relatively simple stomach portion, but the large intestine is much more complex and voluminous than the carnivores In ruminants (cattle, sheep and goat), the stomach is extensively large and complex, whereas the large intestine is relatively small, hence they are known as FOREGUT DIGESTERS  Parts of the Alimentary Tract/Canal CATTLE, SHEEP, GOAT, RABBIT, HORSE BUFFALO (Monogastric) SWINE (Polygastric) POULTRY Mouth (Monogastric) Mouth (Monogastric) Pharynx Pharynx Mouth Beak = Mouth Pharynx Esophagus Esophagus Pharynx Esophagus Stomach Stomach Pre-crop Esophagus Rumen (paunch) Small Intestines Crop Stomach Reticulum (“honeycomb”) Post-crop Esophagus Small Intestines Cecum Omasum (“manyplies”) Proventriculus (“true (Functional) stomach”) Cecum Abomasum (“true stomach”) Large Intestines Ventriculus (“teeth”) Large Intestines Small Intestines Rectum Small Intestines Rectum Cecum Ceca (Paired) Anus Large Intestines Anus Large Intestines Rectum Rectum Anus Anus TAKE A LOOK AT THE FIGURES BELOW TAKE A LOOK AT THE FIGURES BELOW  FUNCTIONS OF THE DIGESTIVE SYSTEM 1. Prehension and Ingestion 2. Mastication or chewing 3. Deglutition or swallowing 4. Gastric and Intestinal Digestion 5. Absorption of nutrients 6. Excretion / elimination of waste  Digestion Process Prehension – Bringing food to the mouth Mastication – Chewing Deglutition – Swallowing Gastric and Intestinal Digestion – Digestion in the stomach and the intestines Absorption – of nutrients Assimilation – utilization of nutrients in the body Excretion / Egestion – elimination of waste Retrieved 01/05/2023, from: Catabolism Definition and Examples - Biology Online Dictionary  Digestion Breaking down of large nutrient macromolecules into simpler molecules for use by an organism. Carbohydrates: Glucose Proteins: Amino Acids Lipids: Fatty Acids/Glycerol  How is Digestion Accomplished? Physical and mechanical actions Chewing and muscular contractions Chemical Action Hydrochloric Acid (HCL) and Bile Enzymatic Action Produced by the animal and micro-organisms to aid in breaking down food  ORGANS OF DIGESTION Mouth (Buccal cavity) Cavity where the organs of prehension are lodged such as lips, teeth, tongue and beak in birds Functions: a. Mechanical digestion: Initial breakdown of food particles through mastication / chewing b. Bolus formation: Ground food mass + saliva moved by the tongue to the pharynx during swallowing Saliva aids in swallowing It is a mixture of serous and mucus fluids produced by three sets of salivary gland It contains ptyalin which acts on the starch in the food  1. THE MOUTH / BUCCAL CAVITY Serves a valuable role for the consumption of food / feed Provides for the initial partial size reduction of feed though grinding TEETH serve the main role in grinding to reduce food size and increase surface area The first action to begin the chemical breakdown of feed occurs when feed is mixed with saliva The amount of mucus present in saliva is regulated by the dryness or moistness of the food consumed In a DRY DIET, more mucus in saliva is secreted In a MOIST DIET, only an amount to assist with swallowing is secreted Saliva generally contains very low levels of AMYLASE, the enzyme that hydrolyses starch to maltose The contribution of digestive enzymes from saliva is MINOR but still noteworthy  The Salivary Glands …………………. There are three main salivary glands, which include the: PAROTID, MANDIBULAR and SUB-LINGUAL glands Saliva secretion is a reflex act stimulated by the presence of food in the mouth  The Salivary Glands …………………. Zygomatic Parotid Mandibular Sublingual  Functions of Saliva Lubricating action – irreplaceable function; water + mucin are responsible for lubrication Solvent action – dissolves fragments of food and stimulates the taste buds to give food its taste Washing action – cleanses the mouth and prevents decay of leftover food particles lysozyme – supplies a disinfectant action that kills bacteria (high in carnivores) Buffering action – bicarbonates buffer acids in the GI tract to prevent ulcerations Anti-frothing action – prevents ruminal bloat by preventing the formation of a stable foam in the rumen which could block eructation Contains nutrients mucin – protein which is digested and used by microbes urea – harvested by the salivary glands and secreted with saliva P and Na – also present in saliva  The Teeth : DENTITION & DENTAL FORMULA DENTITION used to describe the arrangement of teeth, including their number and types Most mammals are DIPHYODONT (ie, having two generations of teeth: an initial DECIDUOUS set of teeth succeeded by a PERMANENT set of teeth) Elephants, kangaroos, and manatees are POLYPHYODONT, having successive generations of teeth that are continually replaced throughout life. DENTAL FORMULA Method of expressing or describing the total number of teeth in man and animals according to the arrangement This formula is expressed using letters and figures The letters used in this formula are based on the 4 types of teeth: I=Incisor, C=Canine, P=Premolar, and M=Molar The Dental Formula is expressed as: The number of each type of teeth in the upper jaw The number of teeth on one side of the lower jaw The Dental Formula of Common Farm Animals  The Dental Pad of Ruminants A prominent feature of ruminant dental anatomy is that they lack upper incisors, having instead a "DENTAL PAD"  Prehension of Food Prehension is the seizing and conveying of food into the mouth In bipeds (Primates) the HANDS are the prehensile organs Dogs and Cats hold their pray with the FORELIMBS which is passed into the mouth by the head and jaw movements In horse, UPPER LIP, TONGUE and the INCISOR TEETH are the main prehensile organs to collect the food The CLEFTED UPPER LIP in sheep favors close grazing (Grazers), on contrast the UNCLEFTED UPPER LIP in goat (Browsers) In cattle, large strong, rough protrudable TONGUE and INCISOR TEETH OF THE LOWER JAW are the prehensile organs The POINTED LOWER LIP functions as a prehensile organ in swine  IN POULTRY ……….. Chickens, as with most birds, obtain feed with the use of their BEAK, which does not contain lips or teeth (hence, NO CHEWING) Food picked up by the beak enters the mouth As previously mentioned, chickens do not have teeth so they are not able to chew their food The TONGUE IS RIGID and salivary glands are poorly developed https://partnersah.vet.cornell.edu/sites/default/files/ avian_atlas_assets/tongue3%20x750.jpg https://www.poultryworld.net/app/uploads/20 21/04/001_767_IMG_Houdjesnavel_WEB- scaled.jpg  IN POULTRY ……….. The salivary glands secrete saliva which wets the feed to make it easier to swallow The saliva also contains some enzymes which start the digestion of the food eaten The chicken’s tongue is then used to push the feed to the back of the mouth so that it can be swallowed https://www.poultrymed.com/Poultryme Salivary d/UploadFiles/PGallery/20165221243466 Glands 2.jpg https://bestautomaticchickendoor.com/wp- content/uploads/2018/10/How-to-Fall- Faster-in-PUBG-3-1-1200x900.jpg  DIGESTION IN THE MOUTH MONOGASTRIC ORGAN ENZYMES ACTION - PRODUCT DETAIL Buccal Cavity / Mouth Salivary amylase Starch, glycogen,and Neutral or slightly alkaline (ptyalin) dextrin to maltose conditions and glucose Minimal importance Only about 5% of starches are broken down in the mouth RUMINANT Nearly all carbohydrate digestion occurs (>90%) WITHIN THE RUMEN, but under certain circumstances (e.g., high rate of passage), a significant amount of carbohydrate digestion can occur in the small and large intestine  2. THE PHARYNX The pharynx, commonly called the THROAT, is a passageway that extends from the base of the skull to the level of the sixth cervical vertebra It serves both the respiratory and digestive systems by: receiving air from the nasal cavity and receiving air, food, and water from the oral cavity Inferiorly, it opens into the larynx and esophagus The upper part of the pharynx (throat) lets only air pass through https://teachmeanatomy.info/wp-content/uploads/Anatomical-Location- Lower parts permit air, foods, and fluids to pass of-the-Tonsils-Waldeyers-Ring.png The pharyngeal, palatine, and lingual tonsils are located in the pharynx They are also called Waldereyer's Ring  2. THE ESOPHAGUS / GULLET Musculo-membranous tube extending from the pharynx to the stomach The primary function of the esophagus is to carry food and liquid from the mouth to the stomach Once food is chewed and mixed with saliva, it passes though the pharynx (throat) and then to the ESOPHAGUS to the stomach Movement though the esophagus involves muscle peristalsis, which is the contraction and relaxation of muscles to move the food A small muscular flap called the EPIGLOTTIS closes to prevent food and liquid from going down the “wrong pipe” — the windpipe (trachea) IN HUMANS, another small flap called the UVULA helps prevent liquid from passing upward into your nasal cavity https://commons.wikimedia.org/wiki/File:High_rising_epiglottis.JPG  DO OTHER SPECIES HAVE UVULAS? As the latest episode of SciShow explains, uvulas are part of what makes humans so unique. Out of all the mammals on Earth, it's just us and some species of baboons that have them, so go ahead and pat yourself on the uvula (don’t). The uvula facilitates complex speech and allows people to make unique noises such as rolling your "r"s It also helps ward off infection and disease by blocking pathogens off from your throat https://my.clevelandclinic.org/- /scassets/Images/org/health/articles/22674-uvula  As in mammals, the mouth is connected to the IN POULTRY ………. esophagus, also called the GOOZLE or GULLET which is a flexible tube that connects the mouth with the rest of the digestive tract Pre-crop esophagus Pre-crop esophagus carries food from the mouth to the crop Post-crop esophagus another short section of esophagus following the crop which carries feed to the proventriculus (stomach) Post-crop esophagus The CROP, CRAW, or INGLUVIES is the distal end of the esophagus an out-pocketing of the esophagus and is located just outside the body cavity in the neck https://backyardpoultry.iamcountryside.com/wp- content/uploads/sites/3/2020/07/crop-768x1024.jpg region a specialized area for the storage of feed When the crop is empty, or nearly empty, it sends hunger signals to the brain so that the chicken will eat more  In Poultry …………. https://cdn.shopify.com/s/files/1/1407/3744/files/Chick_ Crop_480x480.png?v=1652887958 The CROP is located at the base of the neck as it is viewed externally It is an out-pocketing of the esophagus that provides storage for consumed food The crop evolved for birds that need to move to the open to find feed but are typically hunted by other animals These birds are able to consume relatively large amounts of food quickly and then move to a more secure location to digest the food they consumed Functions of the Crop Although salivary glands of the mouth secrete the digestive enzyme amylase very little digestion actually takes place in the crop – it is primarily a temporary storage pouch Ingesta holding and moistening Feed is moistened and softened Initial breakdown of carbohydrate by amylase Site of fermentation  3. THE STOMACH The stomach is a muscular organ, a specialized dilation of the alimentary canal responsible for: temporary storage of food, initiating the breakdown of nutrients, and passing the digesta into the small intestine The stomach is split into FOUR DISTINCT AREAS / REGION which include the: cardiac, fundic, body and pyloric regions The entire stomach is motile It has a pH of 0.9 to 1.5 Retrieved 01/05/2023, from: Figure-13-Cross-section-of-a-typical-segment-of-the-intestinal-wall-showing- the-four.jpg (805×577) (researchgate.net)  3. THE STOMACH All 3 regions of the stomach contain secretory glands located in so-called “GASTRIC PITS” The stomach wall is lined with millions of gastric pits giving it the appearance of a well- used pincushion They mark the entry to each gastric gland, which secretes a complex digestive fluid referred to as GASTRIC JUICE into the stomach lumen  The Gastric Gland …. The upper part of the gland is known as NECK or ISTHMUS The gastric gland epithelium contains five types of cells, which also appear in other regions of the stomach mucous cells stem cells parietal / oxyntic cells chief cells endocrine cells https://doctorlib.info/physiology/medical/medical.files/image1840.jpg The Gastric Pits …… Structurally, the gastric pits are similar, but they contain different cell types The epithelial lining of the stomach mucosa and lining of the pits are covered with surface mucous cells, which secrete a protective coat of tenacious alkaline mucus Function: to protect the epithelium against injury from acid and grinding activity MUCOUS CELLS, located in the neck of the gastric glands, release liquid thin sulfated mucus and proteases As the only cells of the stomach lining, mucous neck cells divide and migrate either down into the gland or up into the pits and differentiate into any of the mature cell types STEM CELLS, found in the upper part of the neck of the gastric glands are in charge of the of renewing the superficial epithelium, as well as the other cell types of the gland epithelium  The Gastric Pits …… The gastric pits of the FUNDIC MUCOSA contain HCl-producing parietal cells that are clustered in the neck of the gland PARIETAL OR OXYNTIC CELLS, are also found in deeper parts of the glands, release Hydrochloric Acid which is responsible for creating a low pH environment in the stomach HYDROCHLORIC ACID (HCL) secretion by the oxyntic cells results in a low pH of 1.5 to 2.5 This reduced pH kills bacteria ingested with the feed https://doctorlib.info/physiology/medical/medical.files/image1840.jpg  The Gastric Pits …… Other secretions in the fundic region are digestive enzymes, specifically PEPSINOGEN secreted by the CHIEF CELLS They are the smaller cells of the gastric glands and mostly located in the deeper part of the gland They show basophilic cytoplasm due to the high amount of PEPSINOGEN, inactive protease precursor which is activated by acidity to form active pepsin The release of pepsin is induced by Gastrin, Histamine and Acetylcholine, but inhibited by Somatostatin ENDOCRINE CELLS are distributed all over the gastric mucosa. They can be distinguished morphologically and release several hormones and https://doctorlib.info/physiology/medical/medical.files/image1840.jpg neurotransmiters  Regions of the Mammalian Monogastric Stomach Pepsinogen is then activated by the hydrochloric acid to form PEPSIN, which is involved with the denaturation of proteins CHON is digested / acted upon by stomach to an appreciable degree https://resources.iacademy.com/46/1004/6490/1473968750/020-010.png In addition, the fundic mucosa also contain: D cells that produce endocrine / paracrine SOMATOSTATIN, which inhibits release of stomach acids to reduce stomach acidity endocrine G cells that produce GASTRIN, which stimulates release of stomach acids to increase stomach acidity Enterochromaffin-like (ECL) cells that produce SEROTONIN Histamine-immunoreactive cells and mast cells that produce HISTAMINE  Regions of the Mammalian Monogastric Stomach The ESOPHAGEAL REGION is located at the entrance of the stomach from the esophagus This region of the stomach does not secrete digestive enzymes but has significance in that this is where ulcer formation in pigs occurs Irritation in this area due to fine particle size, stress or other environmental factors can contribute to ulcer formation in swine Once food passes though this region, it enters the CARDIAC REGION In the cardiac portion of the stomach, mucus is secreted and mixed with the https://resources.iacademy.com/46/1004/6490/1473968750/020-010.png digested food  Regions of the Mammalian Monogastric Stomach Food then passes into the FUNDIC REGION which is the first major portion of the stomach that begins the digestive proces The FUNDIC REGION, which includes the FUNDUS and the BODY, is characterized by having moderately deep gastric pits (folds of the epithelium), with up to seven gastric glands ending in https://resources.iacademy.com/46/1004/6490/14 https://svineproduktion.dk their deeper parts 73968750/020-010.png The BODY, or intermediate region of the stomach, is the central and largest portion  Regions of the Mammalian Monogastric Stomach Periodic contractions churn and knead food into a semifluid mixture called chyme; Rhythmical pumping (peristaltic) waves move food toward the bottom of the stomach, which is the PYLORIC REGION The PYLORUS / PYLORIC REGION is responsible for secreting mucus to line the digestive membranes to prevent damage from the low pH digesta as it passes to the small intestine https://resources.iacademy.com/46/1004/6490/1473968750/020-010.png  The pyloric sphincter …….. The pyloric sphincter facilitates emptying the contents of the stomach to the small intestines and regulates the amount of chyme (digesta) that passes into the small intestine This is an important function not to overload the small intestine with chyme so proper and efficient https://resources.iacademy.com/46/100 4/6490/1473968750/020-010.png digestion and absorption of nutrients occurs Once the chyme leaves the stomach, the material is quite FLUID in consistency https://www.sciencephoto.com/media/1019454/view  IN BIRDS the Stomach Consists of Two Parts The PROVENTRICULUS, also called the glandular stomach or true stomach, is located caudal to the crop and is functionally equivalent to the mammalian stomach where the first significant amount of digestive juices are added It secretes HYDROCHLORIC ACID and PEPSIN, which are used to aid in protein digestion Ingesta passes through very quickly (14 seconds) https://partnersah.vet.cornell.edu/sites/default/files/avian_atlas_assets/Pancreas3%20x750.jpg  IN BIRDS the Stomach Consists of Two Parts The VENTRICULUS, also called the gizzard or the muscular stomach, is caudal to the proventriculus, and is much larger and more muscular in appearance when compared to the proventriculus It has no equivalent in the mammalian gastrointestinal tract The major function of the ventriculus is to grind the food Birds frequently deposit substantial amounts of fat around the gizzard The ventricular contractions result in rotary and crushing movements, which reduce the particle size of hard diets and mix the ingesta with the digestive enzymes In carnivorous and piscivorous species, the ventriculus is primarily a site of food storage rather than contributing to https://partnersah.vet.cornell.edu/sites/default/ mechanical digestion, having evolved to files/avian_atlas_assets/Pancreas3%20x750.jpg digest relatively soft diets  The Gizzard In species with a well-developed ventriculus, a CUTICLE or KOILIN LAYER is present on the surface of the epithelium The cuticle is water-resistant and usually brown, green, or yellow due to the reflux of bile pigments from the duodenum It acts as an abrasive surface to improve the grinding function of the ventriculus and is continuously renewed as it wears down It also protects the underlying mucosa from the digestive action of enzymes Muscular contractions occur every 20-30 seconds https://images.slideplayer.com/ May contain GRIT eaten by the bird to facilitate 18/6098026/slides/slide_29.jpg digestion as well as HCl and pepsin secreted in proventriculus The ventriculus empties into the small intestine, which consists of the duodenum, the jejunum, and the ileum which is similar to other monogastrics  The Stomach of Monogastric Herbivores PSEUDORUMINANTS / HINDGUT FERMENTERS simple stomach, functional cecum (ex. rabbit, horse)  The Stomach of Polygastrics RUMINANTS / FOREGUT FERMENTERS True ruminants have one stomach with FOUR COMPARTMENTS: the RUMEN, RETICULUM, OMASUM, and ABOMASUM Many different animals are ruminants, including: Cattle Sheep Goats Water buffalo Deer Elk Giraffes Camels  The Stomach of Other Farm Animals POLYGASTRIC / RUMINANT / FOREGUT FERMENTERS The ruminant stomach occupies almost 75% of the abdominal cavity filling nearly all of the LEFT SIDE and extending significantly into the right side The relative size of the four compartments to the volume of the total stomach is as follows: the rumen and reticulum - 84% the omasum - 12%, and the abomasum - 4%  The Ruminant Stomach The process of digestion begins with the first two chambers of the stomach, the RUMEN and RETICULUM by softening the ingested matter The rumen compartment acts as storage for chewed vegetation and formation of balls called cud (BOLUS) Cud consists of large, non-digestible pieces of plant matter must be regurgitated, chewed a second time and swallowed before continuing through the process BOLUS is later regurgitated & remasticated at regular intervals during RUMINATION or “chewing the cud” Digested fibers are then sent into the next chamber (OMASUM) where further bacterial action takes place before it is passed on to the ABOMASUM  Ruminants eat rapidly, swallowing much of their feedstuffs without chewing it sufficiently (< 1.5 inches) Rumination "cud chewing“ or RUMINATION IS A NECESSITY Rumination is REGURGITATION of ingesta from the reticulum, followed by REMASTICATION, REINSALIVATION and RESWALLOWING It provides for effective mechanical breakdown of roughage and thereby increases substrate surface area to fermentative microbes Regurgitation is initiated with a CONTRACTION from the RETICULUM distinct from the primary contraction This contraction, in conjunction with relaxation of the distal esophageal sphincter, allows a bolus of ingesta to enter the esophagus The bolus is carried into the mouth by reverse After remastication and reswallowing, peristalsis the food bypasses the two chambers The FLUID in the bolus is squeezed out with the of the stomach and directly enters the tongue and reswallowed third chamber (OMASUM) The BOLUS itself is remasticated then reswallowed  The Rumen fills ½ to three - quarters of the abdominal cavity also called “paunch” or “fermentation vat” functions as a an organ of digestion – a fermentation vat, an organ of maceration , a site for bacterial digestion Muscular contraction of rumen wall churns and mixes food with water and saliva Typically, the rumen and reticulum are considered one organ referred to as the RETICULORUMEN because they have similar functions and are separated only by a small muscular fold of tissue  The reticulorumen is home to BILLIONS of Rumen Microbes….. microorganisms (microbes or “RUMEN BUGS”) that include bacteria, protozoa, and fungi These microbes ferment and break down plant cell walls into their carbohydrate fractions and produce VOLATILE FATTY ACIDS (VFAS), (including LACTIC ACID) such as: ACETATE (used for fat synthesis), PRIOPIONATE (used for glucose synthesis), and BUTYRATE The animal later uses these VFAs for energy Bacteria and protozoa multiply rapidly and elaborate Vitamin B – complex as well as Vitamin C and Vitamin K 60 to 70% of cellulose are digested in the They later serve as protein source for the rumen by bacterial action animal when digested by enzymes  Rumen Microbes Source: Kamra DN. Rumen microbial ecosystem. Curr Sci 2005;89:124–35  The Reticulum Smallest section of the compound stomach (5% of total volume) Most anterior of the compartments and usually located underneath the left sixth to eighth rib Located behind the diaphragm adjacent to the heart “HARDWARE STOMACH” or HONEYCOMB traps and collects heavy/dense objects the animal consumes such as foreign materials like nails, splinters, wires and grits of stone The main function of the reticulum is to collect smaller digesta particles and move them into the omasum, while the larger particles remain in the rumen for further digestion  Hardware Disease When a ruminant consumes a nail, wire, or other sharp heavy object, it is very likely the object will be caught in the reticulum During normal digestive tract contractions, this object can penetrate the reticulum wall and make its way to the heart, where it can lead to hardware disease or TRAUMATIC RETICULOPERITONITIS Develops as a consequence of perforation of the reticulum Most common in mature dairy cattle, occasionally seen in beef cattle, and rarely reported in other ruminants Perforation of the wall of the reticulum allows leakage of ingesta and bacteria, which contaminates the peritoneal cavity causing pleuritis and sometimes pulmonary abscessation; and pericarditis in the pericardial sac (sometimes followed by myocarditis)  Hardware disease can be difficult to conclusively diagnose, but can be prevented by the oral administration of a MAGNET before the animal reaches the age of one  The Omasum “book”, many plies, Stockman’s bible, or Butcher’s bible 7% of total stomach volume Presents many folds of membranes of varying height and width Water absorption occurs in the omasum Excess moisture from ingesta is absorbed Cattle have a highly developed, large omasum Feed is ground more finely than the rumen and reticulum http://extension.msstate.edu/sites/default/files/publica Food molecules compacted tion-images/P2503/omasum.jpg further then passed to the fourth https://www.doctorc.net/Labs/Lab21/IMAGES/omasu chamber – the ABOMASUM m%20copy.jpg  The Polygastric Stomach ABOMASUM The abomasum is the “true stomach” or glandular stomach of a ruminant It is the compartment that is most similar to a stomach in a nonruminant which consists of fundic region, body and pyloric region The abomasum produces HYDROCHLORIC ACID and digestive enzymes, such as PEPSIN (breaks down proteins), and receives digestive enzymes secreted from the pancreas, such as Pancreatic Lipase (breaks down fats) HCl activates pepsinogen to pepsin to digest CHON Ptyalin continues digestion of starch into dextrose and maltose These secretions help prepare proteins for absorption in the intestines The pH in the abomasum generally ranges from 3.5 to 4.0 The CHIEF CELLS in the abomasum secrete mucous to protect the abomasal wall from acid damage Final digestion in the stomach is carried by the abomasum and then passed to the intestine  Stomach Secretions = Gastric Juices Rennin HCl from abomasum Decreases pH (~2-3) Clots milk Denatures protein Lipase Kills bacteria Some species Activates pepsinogen Mucus Influenced by: Protects lining from acid and the amount of protein in a meal, enzymes meal volume, Ensures no “autodigestion” hormones that indirectly affect the acidity of the stomach Lubricant ADRENOCORTICOTROPIC HORMONE [ACTH] Pepsinogen ↑ HCl production Activated form is pepsin Secretin ↓ HCl via the release suppression of gastrin Hydrolyzes protein  Gastrointestinal Hormones Gastrin Cholecystokinin (CCK) Origin: Stomach, Abomasum Origin: Duodenum Stimulus: Food in stomach Stimulus: Fat & protein in duodenum Function: Function: Stimulates HCl & pepsinogen Stimulates bile and pancreatic secretion, increases stomach secretions Also regulates appetite motility and feed intake Secretin Gastric Inhibitory Protein (GIP) Origin: Duodenum Origin: Duodenum Stimulus: Acid Stimulus: Fats and bile Function: Function: Stimulates pancreatic secretions Inhibit stomach motility and Slows stomach motility and acid secretion of acid and enzymes production  CHO Digestion in the Stomach MONOGASTRICS ORGAN ENZYMES ACTION – PRODUCT DETAIL When carbohydrates reach the stomach NO FURTHER CHEMICAL BREAKDOWN OCCURS because the amylase enzyme does not function in the acidic conditions of the stomach BUT THE MECHANICAL BREAKDOWN IS CONTINUOUS — the strong peristaltic contractions of the stomach mix the carbohydrates into the more uniform mixture of chyme RUMINANTS ORGAN ENZYMES ACTION – PRODUCT DETAIL Rumen, Organism Cellulose to glucose Acetic, Propionic and Reticulum, cellulase Butyric Acids absorbed Omasum Organisms killed by acid medium  CHONS Digestion in the Stomach MONOGASTRICS ORGAN ENZYMES ACTION – PRODUCT DETAIL Stomach PEPSIN from Proteins to peptones Acid conditions gastric juice RUMINANTS ORGAN ENZYMES ACTION – PRODUCT DETAIL Rumen, Organisms Proteins to non-protein Improves both quantity Reticulum, nitrogen to organism and quality of feed protein Omasum proteins Abomasum Pepsin from Proteins to peptones Under acid conditions, the gastric juice organisms are killed and digested  LIPID Digestion in the Stomach MONOGASTRICS ORGAN ENZYMES ACTION – PRODUCT DETAIL Stomach - Fat warmed and melted Assumes liquid or semi- liquid form RUMINANTS ORGAN ENZYMES ACTION – PRODUCT DETAIL Rumen, Organisms Some fat to glycerol and Fat melted Reticulum, fatty acids Omasum Reticulum Organisms Omasum Organisms Poor quality fatty acids may be improve by organism activity Abomasum ………………………NOT INVOLVED…………………………… 4. THE SMALL INTESTINES Digesta entering the small intestine mix with secretions from the pancreas and liver, which elevate the pH from 2.5 to between 7 and 8 This higher pH is needed for enzymes in the small intestine to work properly Bile from the gall bladder is secreted into the first section of the small intestine, the duodenum, to aid in digestion Active nutrient absorption occurs throughout the small intestine, including rumen bypass protein absorption in ruminants Muscular contractions aid in mixing digesta and moving it to the next section  4. THE SMALL INTESTINES A tube connecting the stomach to the cecum and large intestines Primary organ of digestion where enzymatic digestion takes place thru the action of various enzymes The Small Intestines has 3 Parts: the DOUDENUM, JEJUNUM, and ILEUM DUODENUM The duodenal portion is the most cranial, closely attached to the stomach and is significant because it contains the pancreas in an S-shaped curve called DUODENAL LOOP The secretions of the pancreas called PANCREATIC JUICE contain enzymes, which enter the duodenum through the pancreatic ducts This is where the bile ducts also pour their The SMALL INTESTINES is the active site of nutrient secretions from the gallbladder digestion and absorption  The Intestines has 3 parts …………………. JEJUNUM Second and LONGEST part of the small intestines; several feet long Has no distinct demarcation from either the duodenum and ileum Digestion continues here The jejunum helps to further digest food coming from the stomach MAIN FUNCTION: Active site of nutrient absorption Absorbs the end products of digestion such as nutrients (vitamins, minerals, sugars, fatty acids, amino acids) and water from food Forms a connection to the large intestines In many species, the jejunum wall is covered with microscopic “finger-like” projections called VILLI which may number in MILLIONS These increase intestinal surface area to aid in nutrient absorption Villi increase the absorptive surface tremendously Both the jejunum and ileum are peritoneal (relating to, by means of, or enclosed by the peritoneum, the membrane lining the abdominal cavity)  The Intestines has 3 parts …………………. https://www.researchgate.net/profile/Devin- Holman/publication/317098350/figure/fig1/AS:497597795311616@1495647 968030/Diagram-of-the-swine-gastrointestinal-tract-with-major-sections- indicated-as-well-as.png  The Intestines has 3 parts …………………. ILEUM the caudal part of the intestines The DNES (Diffuse The function of the ileum is mainly to absorb Neuroendocrine System) cells of vitamin B12 and bile salts and whatever the ileum secrete various products of digestion were not absorbed by the hormones into the blood: jejunum GASTRIN, SECRETIN, CHOLECYSTOKININ Cells in the lining of the ileum secrete the PROTEASE and CARBOHYDRASE enzymes responsible for the final stages of protein and carbohydrate digestion https://www.researchgate.net/profile/Devin- Holman/publication/317098350/figure/fig1/AS:497597795311616@1495647968030/Diagram- into the lumen of the intestine of-the-swine-gastrointestinal-tract-with-major-sections-indicated-as-well-as.png Absorptive Structures of the Small Intestines Lumen Mucosa Villi small nipple-like projections which aid in muscular digestion and absorption of nutrients Crypts Lacteal principally concerned with absorption of fats and fatty acids ; To a lesser extent, it also absorbs CHO and CHONS Enterocyte Brush border  Secretions Entering the Small Intestines Intestinal mucus Brush border enzymes Secreted from within SI Pancreatic juices – Produced & stored in pancreas Bile – Produced in the liver – Stored in gallbladder – HORSE HAS NO GALLBLADDER Enters from ducts into SI Direct bile secretion into duodenum Cannot store bile so they must have continuous intake of food  Nutrient Absorption in the Small Intestines Principal site of absorption of amino acids, vitamins, minerals and lipids Glucose and other sugars in monogastrics Generally, most absorption occurs in the proximal (upper) part of the small intestine but some absorption occurs in all segments Duodenum, jejunum and ileum Digestion and absorption within SI is rapid Within 30 minutes of entering SI  CHO Digestion in The Small Intestines MONOGASTRICS & RUMINANTS ORGAN ENZYMES ACTION – PRODUCT DETAIL Small Intestines Duodenum Pancreatic Starch, glycogen and AMYLASE dextrin to simpler from pancreatic sugars juice MALTASE Maltose to glucose Final breakdown to simple sugars SUCRASE Sucrose to fructose and glucose LACTASE Lactose to galactose and glucose Ileum - - Simple sugars absorbed  CHONS Digestion in The Small Intestines MONOGASTRICS & RUMINANTS ORGAN ENZYMES ACTION – PRODUCT DETAIL Small Intestines TRYPSIN from Proteins and peptones Acidity reduced by pancreatic to polypeptides pancreatic juice, bile juice and intestinal juice Duodenum CARBOXY- Polypeptides to PEPTIDASE dipeptides Ileum AMIN- Dipeptides to amino Amino acids absorbed by PEPTIDASES acids the body DIPEPTIDASES  LIPID Digestion in The Small Intestines MONOGASTRICS ORGAN ENZYMES ACTION – PRODUCT DETAIL Small Intestines Duodenum LIPASE from Fat to glycerol and organic Some fats broken down pancreatic juice acids Absorption as glycerol and organic acids including oil droplets RUMINANTS ORGAN ENZYMES ACTION – PRODUCT DETAIL Small Intestines Duodenum Lipase from Fat to glycerol and organic More rapid digestion than non- pancreatic juice acids ruminants due to initial breakdown Ileum Absorption either as oil droplets or glycerol and fatty acids  Nutrient Absorption in the Small Intestines Variety of Absorption Mechanisms Passive Transport Diffusion Facilitated diffusion Active transport Exocytosis Pinocytosis or endocytosis Dependent upon a. Solubility of the nutrient (fat vs. water) b. Concentration or electrical gradient c. Size of the molecule to be absorbed Simple Diffusion Occurs across a semipermeable membrane Requires a concentration gradient across the cell membrane It is a passive transport mechanism thus require no energy expenditure by the cell Does not need a carrier transport protein Happens by random motion Cannot be inhibited by an inhibitor molecule because of the absence of carrier proteins Non-specific to any particle A comparably slow process than other forms of diffusion  Occurs due to the Facilitated Diffusion random motion of molecules (Brownian motion) Requires a biological membrane for transport Requires a carrier protein, thus also known as carrier-mediated diffusion Does not require energy expenditure and use of high energy phosphate molecules – ATP  Pinocytosis Primarily occurs when a cell absorbs nutritional or waste droplets suspended in external fluid The nutritional molecules that can activate pinocytosis include fats, sugars, proteins, ions or other small molecules This process begins when a soluble substrate binds to the surface of a cell After a substrate opportunistically binds to the cell membrane, the cell continues pinocytosis by gathering external fluid into a membrane-bound pocket vesicle called a PINOSOME This pinosome continues to pinch off from the cell membrane within the cell until it is fully internalized  Exocytosis Process by which cells release molecules TO THE OUTSIDE OF THE CELL By exocytosis, cells transport molecules to the plasma membrane and many cells also release proteins to the extracellular fluid Constitutive Exocytosis: the default pathway of exocytosis Cells carry out constitutive exocytosis in order to transfer molecules from the Golgi network to the external environment of the cell It is important in transporting proteins like receptors that function in the plasma membrane.  Exocytosis Regulated Exocytosis: a more specialized form of exocytosis that is triggered in response to specific conditions, signals or biochemical triggers from the outside Cells release materials in a highly regulated manner Secretory materials are first accumulated in secretory vesicles Cells release cytokines, hormones, neurotransmitters, neuropeptides and other small signaling molecules this way  5. THE CECUM Somewhat comma-shaped blind sac situated at junction of small and large intestine Located between the ileum and large colon consisting of a body, base and apex The colon is the site of most of the water absorption in the large intestine IN MONOGASTRICS: Microbial activity and digestion of feeds but of little importance to most animal species Contains cellulolytic and hemicellulolytic microbial population similar to the rumen POULTRY have two ceca just before the rectum IN RUMINANTS: The cecum serves little function in a ruminant, unlike its role in horses IN MONOGASTRIC HERBIVORES (hind gut fermenters): What makes monogastric herbivores or hindgut fermenters unique is they have an active cecal bacterial population that break down cellulose, starches and other digestible fibers and via fermentation The CECUM is home to symbiotic bacteria and exceptionally large and complex compared to ruminants and non-herbivorous monogastrics The cecum can hold 10x more material than the stomach, and, on average, 40% of the food material is in the cecum at any given time Rabbit  Digestion in hindgut fermenters …. After about 1.5 h in the small intestines, the feed particles that have not been degraded enter the caecum Approximately half of the content is coarse and fine feed particles that were not previously degraded The other half is bacterial bodies that have developed in the caecum at the expense of the elements coming from the small intestine, as well as the remains of digestive secretions also from the small intestine They remain in the cecum for 2-12 h, during which they are attacked by the bacterial enzymes in the caecum The end products of fiber digestion are VOLATILE FATTY ACIDS which then penetrate the cecum walls and are absorbed into the blood The content of the cecum in turn is evacuated to the colon TILL THIS POINT , the function of the digestive tract of the rabbit is no different from other monogastrics  Hindgut Fermenters / Monogastric Herbivores The digestive tract of a rabbit is very similar to that of a horse Both are “HINDGUT FERMENTERS,” they have an organ called the “CAECUM” that acts similarly to a cow’s rumen so it can consume a fairly high amount of fiber from the forage in its diet BUT: the cecum is located at the END of the digestive tract rather than at the BEGINNING SO: their cellulose digestion is not as efficient as the ruminants since cecum is DOWNSTREAM of the digestive organs (stomach and small intestine) Because the beginning of the digestive tract is like that of a monogastric animal (such as pigs and humans) fiber is not efficiently digested HENCE: the fiber quality must be HIGH https://resources.cdn.yaclass.in/24bb617d-a436-47ad-9343- Rabbits and horses will not do well at all ON COARSE, ec097318de0a/shutterstock786595840w10001w400.jpg VERY MATURE FIBER SOURCES Good quality fiber is a major energy source and an effective tool for maintaining a healthy microbial population in the cecum which is critical for proper digestion and optimal gut health  The dual nature of the functions of the proximal colon is unique This dual function the colon produces two different kinds of feces: HARD FECES and CECOTROPHS If the content enter the colon early in the morning, it undergoes few biochemical transformations It is a different matter if the caecal content passes into the colon at another time during the day The colon contracts in ALTERNATING DIRECTIONS: some of these contractions tend to empty the contents "normally" others send it back towards the caecum Most of the liquid fraction, which contains soluble products and the fine particles (smaller than 0.1 mm, a dimension which includes the bacteria), is brought back to the caecum, The colic wall secretes a MUCOUS which progressively envelopes the pellets formed by the contractions of the large intestine wall These pellets form an elongated cluster, called SOFT FAECES or "CAECOTROPHS“ also referred to as the night droppings RABBITS EAT THESE CAECOTROPHS and the essential nutrients are extracted as the indigestible fiber passes through their body a second time (CECOTROPHY)  The dual nature of the functions of the proximal colon is unique The "solid" fraction containing the coarse particles (larger than 0.3 mm), forms the HARD FECES which are excreted out of the rabbit (Björnhag, 1972) This process of producing hard and soft pellets helps to stimulate the rabbit’s digestive system and appetite In a healthy rabbit fed on a balanced diet, CECOTROPHY provides approximately 15 - 25 % of the daily protein intake and covers the total requirements of vitamins B and C Cecotrophy is critical to keeping the GI tract healthy and functioning  CECOTROPHY / COPROPHAGY The beginning of the colon, called the proximal colon, separates the food material into digestible and indigestible material The INDIGESTIBLE MATERIAL is formed into hard fecal balls and moved out of the GI tract during or shortly after eating The DIGESTIBLE MATERIAL is moved backwards into the cecum Some nutrients are absorbed through the cecal wall Digestible fiber is formed into smaller, softer CECOTROPHS which are eliminated rectally The cecotrophs have a more pungent odor are often passed at night OR at least 4 hours after eating and ingested directly from the anus Their chemical composition can be seen in the table below  6. THE LARGE INTESTINES The large intestine is the last part of Degree of development is species dependent the digestive system After the small intestine has removed all available nutrients from the feed, the remaining material is passed into the large intestine As material passes through the large intestine, water is absorbed back into the animal’s body Shorter than the small intestine but larger and sacculated as compared to the small intestines It is composed of 3 segments: (a) Cecum; (b) Colon; (c) Rectum It starts at the cecum, which is like a sack where the fibrous part of the animal's ration is digested The colon comes after the cecum The large intestine IN POULTRY consists of The colon is divided into ascending, transverse a pair of ceca (instead of one as in other and descending parts monogastrics) and a short straight intestine, The large intestine terminates at the rectum and called the colon or rectum anus Rectum is the area where the feces accumulate  IN POULTRY, but not in cattle, sheep or pigs, the inner surface area of the large intestine is expanded by villi and the equivalent of anus is the cloaca The large intestine is very short (2-4 in) and empties into cloaca where fecal material will be voided via the VENT  6. THE LARGE INTESTINES The mucosa of the large intestine has NO VILLI, but columnar epithelial cells with microvilli formed into straight tubular crypts Numerous goblet cells secreting SULPHATED CARBOHYDRATE- PROTEIN complex intersperse the columnar cells to lubricate the colon https://labster-image-manager.s3.amazonaws.com/v2/GIA/dcdac702-6315-4cce-b76e- a1e581378435/GIA_IntestinalWallStructure_Comparison.en.x1024.png  Functions of the Large Intestines Fermentative digestion of fiber (production of volatile fatty acids) No enzyme secretion Relies on microbes or secretions washed out of the SI Somewhat limited in the monogastric Absorption of remaining water, volatile fatty acids (VFAs) from microbial fermentation and minerals Digesta storage Absorption of liquid Mass movements move fecal matter to anus usually only a few times a day Associated with defecation Bacteria in the Large Intestines: Cellulolytic – digest cellulose (forages); Amylolytic – digest starches and sugars (concentrates or grains); Other types: Proteolytic: Clostridium; Organic acid utilizers: Methanogens - Produce CO2, H2, formate, CH4  CHO Digestion in The Large Intestines MONOGASTRICS ORGAN ENZYMES ACTION – PRODUCT DETAIL Large Intestines Organism Cellulose breakdown Acetic, proprionic, and (Cecum and fermentation butyric acids absorbed Colon) by the body RUMINANTS ORGAN ENZYMES ACTION – PRODUCT DETAIL Large Intestines Organism Cellulose breakdown Of small value since initial (Cecum and fermentation fermentation of greater Colon) importance and value CHON and LIPID Digestion in The Large Intestines – minimal / not significant  7. THE RECTUM Any remaining undigested matter is finally excreted from the body through the rectum and anus The rectum is embedded in fat and is dilated to form AMPULLA RECTI just before ending at the anus The rectum has a simple structure with columnar cells and only few goblet cells The rectum is a chamber that begins at the end of the large intestine, immediately following the sigmoid colon, and ends at the anus Ordinarily, the rectum is empty because stool is stored higher in the descending colon Eventually, the descending colon becomes full, and stool passes into the rectum, causing an urge to move the bowels (DEFECATE) The rectum of birds is similar to the rectum of https://cdn.lecturio.com/assets/Gross-anatomy-of-the-rectum-and-anal-canal-1.jpg mammals  8. THE ANUS The Anus is terminal part of the alimentary canal and is continuous with the skin It is the opening at the far end of the digestive tract through which stool leaves the body The anus is formed partly from the surface layers of the body, including the skin, and partly from the intestine The anus is lined with a continuation of the external skin A muscular ring (ANAL SPHINCTER) keeps the anus closed until the person has a bowel movement 3 Major Muscles of the Anus Sphincter Ani Internus thick muscle Sphincter Ani Externus located outside the internal sphincter Retractor Ani retracts the partial prolapse that the anus undergoes during defecation https://ars.els-cdn.com/content/image/3-s2.0-B9780323476744000761- Feces includes sloughed cells, undigested food and f076-001-9780323476744.jpg microbial matter  In Poultry …… The equivalent aperture to the anus is part of a compound structure called the CLOACA The cloaca is divided into three regions but these are difficult to distinguish The rectum enters the cloaca at the COPRODEUM, the urinary and genital ducts enter at the URODEUM and the opening to the exterior is called the PROCTODEUM Dorsal to the proctodeum is a region of lymphoidal tissue called the Bursa of Fabricius https://www.semanticscholar.org/paper/Age-related- morphological-change-in-bursa-of-of-Singh- Singh/96e40fd56b12bbe6129ddef11ea8177fc871e9db/ https://www.semanticscholar.org/paper/Age-related-morphological-change-in-bursa- figure/2 of-of-Singh-Singh/96e40fd56b12bbe6129ddef11ea8177fc871e9db/figure/0 The Cloaca in Poultry The cloaca is the single posterior opening for a bird's digestive, urinary, and reproductive tracts and is used to expel feces and lay eggs The cloaca is found on the rear of the body under the base of the tail, covered by feathers on the extreme lower abdomen In cocks, the sperm ducts and in females, the oviduct have their openings in the cloaca The cloaca and the area of the body where it is located, as well as the physical slit opening itself, is also frequently called the VENT  When fecal material is excreted, the cloaca folds back at the vent allowing the rectal opening of the large intestine to push out, closing the reproductive tract opening ACCESSORY ORGANS OF DIGESTION: LIVER Major role in digestive process is to provide BILE SALTS to small intestine Needed for digestion and absorption of fats – Bile Produced by the liver Stored in the gallbladder Synthesized from cholesterol The duodenum receives secretions from the gallbladder via the common duct Fat digestion products are absorbed in the first 100 cm of small intestine The primary and secondary bile acids are reabsorbed almost exclusively in the ileum returning to the liver by way of the portal circulation (98 to 99%)  Bile Acids …. CHOLIC ACID is the bile acid found in the largest amount in bile Cholic acid and CHENODEOXYCHOLIC ACID are referred to as primary bile acids Bile acids are converted to either Glycine or Taurine conjugates Glycocholate – 24% Glycochenodeoxycholate – 24% Taurocholate – 12% Taurochenodeoxycholate – 12% Glycodeoxycholate- 16% Taurodeoxycholate – 8% Various lithocholate – 4%  PANCREAS Provides a potent mixture of digestive enzymes to the small intestine Enzymes include Proteases, Carbohydrases, Lipases and Nucleases Produces Sodium Bicarbonate that neutralizes the acidity of the chyme (gut contents) entering the duodenum The pancreas releases its secretions into the pancreatic duct which then join the common duct and the duodenum The pancreatic enzymes are responsible for: 50% of CHO digestion 50% of CHONS digestion 90% of Lipid digestion  Pancreatic Enzymes Lipase Breaks down FATS to Fatty Acids and Glycerol Trypsin Breaks down POLYPEPTIDES to Peptides Chymotrypsin Breaks down PEPTIDES to Amino Acids Amylase Digests STARCH to Disaccharides Sucrase, Maltase, etc. Digests DISACCHARIDES to monosaccharides  Monogastric vs Polygastric Digestive System HIND GUT FUNCTION MONOGASTRIC PLOYGASTRIC FERMENTORS Digest and extract energy Very limited Yes Yes but not as from cellulose (large intestines) efficient as polygastrics (cecum) Utilize dietary sugar sources Yes Yes Yes directly Utilize protein from feeds Yes Yes Yes directly Utilize fat from feeds directly Yes Yes Yes Utilize microbial protein No Yes No  REFERENCES DEROUCHEY, JOEL, B. GOODBAND, M. TOKACH, S. DRITZ AND J. NELSSEN. 2009. Digestive system of the Pig: Anatomy and Function In: Proceedings of the Swine Profitability Conference 2009. Kansas State University. 3 Feb 2009. 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