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ANFS251 Week of 02.15.16

by: Rachel Schmuckler

ANFS251 Week of 02.15.16 ANFS251

Rachel Schmuckler

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Lecture notes from Week 2 of class
Animal Nutrition
Dr. Lesa Griffiths
Class Notes
Carbohydrates, Water, GI tract, Ruminant, non ruminant, mono gastric, Animal Science, nutrition
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This 15 page Class Notes was uploaded by Rachel Schmuckler on Thursday February 18, 2016. The Class Notes belongs to ANFS251 at University of Delaware taught by Dr. Lesa Griffiths in Spring 2016. Since its upload, it has received 14 views. For similar materials see Animal Nutrition in Animal Science and Zoology at University of Delaware.

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Date Created: 02/18/16
February 11, 2016 – Animal Nutrition GI tract is a unique system providing the means by which an animal accomplishes:  Digestion of food consumed  Absorption of essential nutrients  Conservation of water  Synthesis of essential vitamins and other nutrients Gastrointestinal Tract and Nutrient Utilization  Convert complex nutrient sources into forms that the animal can absorb and use  Digestion – converting complex feed nutrients into absorbable forms  Absorption – digested nutrients cross the cellular lining (membranes) of the GI  tract Classification of Various Digestive Systems  Based on type of diet o Herbivores – primarily plants o Carnivores – other animals o Omnivores – combination of plants and animals  Based on digestive physiology o Monogastric o Ruminant Classification of Various Digestive systems  Swine – omnivore, monograstic  Poultry – omnivore, monograstic, complex foregut and relatively simple intestinal  tract  Dogs and cats – monograstic carnivores  Horses and mules – monogastric herbivores  Ruminants – consume and digest plant materials and are classified as herbivores (cattle, sheep, goats, deer, elk, many wild species) o Pre­gastric fermenters (versus post­gastric)  Gastric means stomach  Fermentation chamber with a structure full of bacteria before the  stomach – “rumen”  Bacteria = main source of protein  “Cecum” for post­gastric fermenter Proventriculus = stomach Large the structure, more complex the diet  Relative size can provide insight as to where digestion will take place Rabbit  Monograstic herbivore  Complex large intestine  Big cecum Characteristics and Function of Digestive Tract  Mouth and associated structures – beak, teeth, lips, tongue o Primary function  Prehension and preparation of food  Increase surface area, increase what is exposed to digestive enzymes/bacteria  Cattle and sheep will masticate food only to a limited extent before  ingesting  Subsequently regurgitate coarser constituents and  remasticate them  Rumination – decreasing particle size to increase the  surfaces where bacteria can attach  Teeth o Herbivorous  Incisor teeth adapted to nipping off plant material  Molars with flat surfaces grind plant fibers o Ruminants  No upper incisors depend on upper dental pad and lower incisors  (i.e. sheep) o Omnivores  Use incisor teeth primarily to bite off pieces of food (i.e. swine) o Avian  No teeth  Break and or claws reduce food o Carnivores  Teeth adapted to tearing of muscle and bone  Pointed molars are adapted for crushing bones and mastication of  food  Saliva and Swallowing o Good mixed with saliva and formed into bolus  Bolus is coated with saliva (lubricated) o Other functions of saliva  Keeping the mouth moist  Aiding taste mechanisms  Providing digestive enzymes  Acting as a buffer o Salivary Amylase = enzyme  Esophagus o Bolus is transported (swallowed) to GIT  CNS controls contractions  Peristalsis = contractions  Ruminants have two way (regurgitation)  Challenge of the horse is that it is only one way – commonly  chokes  Length varies considerably  Rumination – moving the bolus from reticulorumen to the mouth  Allows the animal to chew its cud  Aids the digestion of fibrous feed components  Glandular Stomach o All stomach/stomach­like structures function the same way  Difference: Location of the stomach  Pre­gastric = rumen  Post­gastric = cecum o Lined with specialized secretory tissues o Contractions of the muscles lining the stomach mix with the bolus gastric  secretions  Amount of muscle varies amongst species  Horse challenge – lacks a muscular stomach o Buildup of fluid causes colic  Muscles contracting to churn the fluids in the stomach to aid  digestion o Regions of the stomach  Nonglandular region – no digestive secretions are produced  Cardiac region – lined with epithelial cells, secrete mucin  Fundic region – three cell types  Parietal – secrete HCl (chemical, not an enzyme)  Neck chief – secrete mucin (protect the stomach from the  acid)  Body chief – secrete pepsinogen, rennin, lipase o Pepsinogen ­ protein enzyme o Lipase ­ fat enzyme o Rennin ­ milk digestion  Plyoric – has only the neck chief and body chief cells o Presence of food causes secretion of HCl and enzymes and begins  contractions of muscular lining o Chyme  The bolus becomes this acidic material resembling a thick slurry  Enters the small intestine (primary site for enzymatic digestion)  Small Intestine o Composed of duodenum, jejunum, ileum o Duodenum  Bile  Neutralizes the pH of chyme to 6.8 to 7.0  Emulsification of fat  Pancreatic enzymes secreted into duodenum to break down fat  Enzymes secreted by duodenum to convert proteins and  carbohydrates into amino acids and monosaccharides o Lined with fingerlike projections called villi that increases surface area  One cell thick for easy absorption  Complexly vascular o Contractions mix the digested food and move it down the GI tract o Digesta pass into the jejunum and ileum  Enzymatic digestion continues  Primary sites for absorption of nutrients in monogastic animals  Large Intestine o Cecum, Colon, Rectum o Microbial digestion o Most nutrients already absorbed  No villi o Type/number of microorganisms depend on the amount of undigested  food constituents  Varies depending on the diet and species  Prevent rapid changes of diet in any animal because it kills the  healthy gut bacteria that are accustomed to that particular diet  Good bacteria will die, bad bacteria will grow  Bad health results (i.e. diarrhea) o Absorption of some organic acids and water o Relative length, diameter, and extent of sacculation vary considerable  among species  Much larger in herbivorous species (i.e. horse, rabbit) o Indigestible components are eliminated via the rectum Small ceca in hawks, large in grouse The big foregut (hoatzin), long midgut (emu), and long colon (ostrich) compensates for  the small ceca Other Functions of the GI tract  Major route for excretion o Liver  Active site of detoxification  Some excretion of mineral elements  Some net excretion in large intestine  Depends on level of mineral stores in the animal and the  number of minerals in the diet  Synthesis of specific nutrients by microbial organisms  Amount of absorption after small intestine is limited, so mostly are excreted o In some animals (particularly rodents and horses) this potential lack of  absorption is circumvented by coprophagy  Enables an animal to survive on diets lacking sufficient vitamins  and amino acids  Material excreted from cecum separately from that of the small  intestine (different poops)  Cecal pellets are nutrient rich from the vitamins made by  bacteria in the cecum o Immediately eaten by the animal Avian Species  Crop: temporary storage  Proventriculus: similar to stomach, gastric secretions produced, less grinding  action than the stomach  Gizzard: tough muscular lining contracts  Crop, proventriculus, and gizzard together function as a stomach, but the  proventriculus contains the acids/enzymes, the crop is the storage, and the  gizzard is the movement  Relatively long small intestine  Two rather large ceca – located in the large intestine (past the main site of  absorption) so the ceca do not contribute highly to the ability to consume a high  forage diet, not very functional  Very short sections of large intestine o Urinary secretions are combined with the feces before being eliminated Ruminant Species  Stomach o Divided into four compartments  Reticulum – honeycomb  Rumen (name for the entire “stomach” structure, but also a part of  the 4 compartments)  Aka Paunch  Allows for a high forage diet  Located before the small intestine  Contains bacteria, nutrients absorbed  Tongue­like projections called papillae  Several strong, muscular pillars which contract in a rhythmic  manner  Causes ingesta to be mixed o Course fibrous feeds regurgitated and re­chewed  Omasum  Contains various­sized leaves extending into the lumen to  prevent large particles from leaving the rumen  Abomasum  Same function as the glandular stomach in monogastric  species o In pseudoruminants, the stomach has only three compartments  Camel and related species  Ingested food subjected to pregastric microbial fermentation  Small intestine – similar to monogastric species o No benefit to feeding ruminants high quality protein because the bacteria  eat it regardless, and they get a good amount of protein from consuming  that bacteria  Bacteria break the feed into volatile fatty acids (VFAs)  Absorbed from cecal wall  From sugars and starch  Absorbed and sued as primary energy source  Readily used but less efficient than if original carbs were  digested and asbored from small intestine  8­20% of carbs consumed converted to methane (wasteful!)  Nonruminants must break food into glucose for energy  Large intestine – considerably larger than omnivorous species Digestive tract of a sheep  Large rumen for microbial fermentation! – main contribution to digestion  Small intestine = absorption  Cecum not as useful, some fermentation, reabsorption of water Rumination  Undigested coarse foods are collected in the reticulum  Formed into a bolus  Moved back up and the esophagus to the mouth for further chewing Eructation  Belching of gas  Microbial fermentation in rumen produces gases (CO2 and methane) which must be eliminated to avoid bloat o Occurs when froth forms in the rumen o Usually after consuming legume species, or a high­concentrate diet (i.e.  grains) o Can inhibit eructation o Results in reduced performance and many deaths (pressure on other  organs) o Cattle swell on the left side Symbiosis  Mutually beneficial relationship between rumen microorganisms and animals  Very favorable environment for microbes – moist, narrow temp range, feed  source, end products removed  Many bacteria types (25­80 billion per ml)  Ciliated protozoa o 35+ species o 20,000­50,000 per ml  Type of organisms depends on feed consumed o High forage diet  High in cellulose and hemicellulose  Relatively in digestible in mammals  Microorganisms digest those substrates o Same for diets high in cereal grains but for starch o Number of organisms affected by feed intake o VFAs and ammonia (nitrogen to amino acids to protein) are end products  of microbial digestion  Continually absorbed across rumen wall  When microbial populations thrive, it greatly affects nutrient requirements of the  host animal  Fibrous digested more efficiently by microbes in the rumen  Cellulose and hemicellulose digested only by microbial enzymes  Bacteria can use simple forms of nitrogen (i.e. urea, ammonia) to synthesize  cellular proteins, reducing dependence on high­quality dietary protein sources  Microbes synthesize adequate amounts of vitamins  Except A, D, and E – fat soluble  No need to worry about giving ruminants water soluble vitamins  Moisture and pH of rumen are maintained by the 150+ liters of saliva secreted  per day in a mature cow  Contains large amounts of sodium bicarbonate o Acts as a buffer and neutralizes acids produced in the rumen Disadvantage:  High quality dietary protein sources are partially degraded to produce ammonia o Resynthesized into microbial protein (medium quality protein) Advantage:  Low quality dietary protein sources are partially regarded when consumed by  bacteria “Pounds per feed per pound of gain” More pounds of feed for ruminants because feeding bacteria before the animal Overall effect of rumen fermentation = animals utilize good quality ingredients less  efficiently than monogastric animals  Differences in feed types and how they are digested illustrate why feed  conversion in ruminants is low Young Ruminants  Born with nonfunctional rumen o Depending on digestion in the abomasum and small intestine o Reticular (or esophageal) groove  Allows milk to bypass reticulorumen  Goes directly to omasum and then abomasum  Escapes bacterial fermentation  Start to consume solid food o Reticulum and rumen start to develop o Fully functional by 8 weeks in lambs and 6­9 months in cattle Differences with Respect to the Types of Diet for Different Species  Avian species do not have the ability to effectively utilize large amounts of fibrous plant materials  Omnivorous species (i.e. swine) can utilize more fiber than avians, but much less than herbivorous species o Adult omnivores do better than young omnivores o Well developed ceca o Less complex digestive tracts, limited ability to digest fibrous plant carbs  Nonruminant herbivorous species (i.e. horse) can survive and do well on plant  materials of much lower quality than that required by swine o Hind­gut fermenters o Developed ceca o No coprophagy  Ruminant animals are well developed to diets that consist primarily of fibrous  plant materials o Pre­gastric rumen o Poor efficiency  tons of food to get nutrients because the bacteria need  to be fed before the animal (caloric cost)  Monogastrics use the calories immediately o Simple stomach and intestines o i.e. poultry o Fed highly digestible diets with high quality nutrient sources Nutrient Utilization  Animals that can use large amounts of forages have a stomach or large intestine  that allow either: o Pregastric microbial fermentation (ruminant) o Postgastric microbial fermentation (horses, rabbits) Carbohydrates Primary component found in livestock feeds  Why not protein? o Necessary for young animals to grow o Older animals use it for repair o Very expensive form of energy  Why not fat? o Expensive o Little supply due to human demand  Carbs o Abundant o Inexpensive Carbohydrate = energy!  Bulk of the diet  Forages  Corn – highly digestible starch Synthesized by plants  Primary building block in most plant materials = glucose  Primary subunit of glucose = carbohydrate  Many different types of carbohydrates coming from different parts of a plant Comprise up to 70% of forage dry matter and 80% of grains No specific dietary requirement for carbohydrates, but rather for energy (calories) Types  Composed of C, H, O  Simplest form = monosaccharide o 5 carbon monosaccharide = pentose o 6 carbon monosaccharide = hexose  Disaccharide = two monosaccharides combined  Polysaccharide = 3+ monosaccharides combined o Complicated polysaccharide chains are indigestible by mammals (only by bacteria in the rumen and cecum) Types of carbohydrates associated with feeds: Common Carbohydrates  Glucose and fructose – most common simple sugars in feed  Sucrose o Glucose + fructose o Found in plants as sugar cane and sugar beets o Highly digestible  Lactose o Glucose + galactose o Only in milk o Lactose intolerant = no enzyme to break apart the glucose and galactose  Maltose o Glucose + glucose o Intermediate breakdown product produced when starches are digestible  Starch and Cellulose o Polysaccharide in plants in the highest concentrations o Starch  Grains (i.e. corn), tubers, and other roots  Links between glucose subunits can be easily digested by mammalian enzymes  Sweet taste o Cellulose  Forages (in the stalks of plants)  Links between glucose subunits cannot be digested by mammalian enzymes  Digested by microbial organisms in GIT  Gums, pectins, hemicelluloses o Occur in varying amounts in some plant material o More indigestible than digestible Absorption and Metabolism  Monogastrics o Dietary carbs converted to monosaccharides o Amylase  Salivary glands of some species  Primary source = pancreas  Starch to maltose o Other enzymes from mucosal lining of the duodenum o Corn, milo, barley, oats = common  Dietary carb levels exceed animal’s ability to digest it - diarrhea occurs  Monosaccharides rapidly absorbed by small intestine and transported via blood to be metabolized as an energy source  Storage o Little stored as carbohydrates o Some glucose stored as glycogen  Rapid release in muscular activity  Regulation of blood glucose  No enzymes to digest cellulose, hemicellulose, and other carbs in fibrous feedstuffs o Occurs in rumen, cecum, colon from microbial action with varying success  Monogastrics: horses > swine, rabbits > poultry, dogs, cats  Ruminants o Young ruminant animals are functionally monogastric  Eat solid food  Bacterial and protozoal populations gradually develop in the rumen  Microbial organisms produce VFAs  Papillae in rumen to develop and mature, enabling the animal to digest more complex carbohydrates (cellulose, hemicellulose) o Fully developed rumen


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