ANFS251 Week of 02/08/16
ANFS251 Week of 02/08/16 ANFS251
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This 8 page Class Notes was uploaded by Rachel Schmuckler on Thursday February 11, 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 27 views. For similar materials see Animal Nutrition in Animal Science and Zoology at University of Delaware.
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Date Created: 02/11/16
February 11, 2016 – Animal Nutrition 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 Pre-gastric fermenters (versus post-gastric) Gastric means stomach Fermentation chamber with a structure full of bacteria before the stomach – “rumen” Bacteria = main source of protein “Cecum” for post-gastric 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/stomach-like structures function the same way Difference: Location of the stomach Pre-gastric = rumen Post-gastric = 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 February 9, 2016 – Help With Plants What are the different types of plants animals eat? Cereal grains = energy Legumes = protein o Beans (i.e. soybeans) o Pasture or forage legumes (i.e. alfalfa, clover) Can be preserved as hay or grazed Grasses (i.e. timothy, rye, fescue) o Can be preserved as hay or grazed as pasture Silage o Can be made from different plants listed above Forbs, shurbs Which ones are considered forages or roughages? Legumes Grasses Silage Forbs, Browse o Found in natural (versus manmade or seeded) pastures Pastures Collections of plants that ruminants and non-ruminant herbivores graze and eat Can be as natural as the vast open spaces in the US o Native grasses and other plants like forbs and shrubs Can be manmade which means a livestock producer has selected a complimentary grouping of plant seeds to plant, fertilize, and manage for animal feed o Excessive growth (beyond what the animals graze) is harvested and preserved as hay for eating at a later time o Combination of grasses and legumes (not bean legumes) is common o Examples: Kentucky bluegrass Orchardgrass Timothy grass Perennial ryegrass Reed canarygrass Tall fescule Tall fescue endophyte (fescue toxicity) Pasture Legumes Symbiotic association with soil bacteria Fix nitrogen High protein, enhance palatability and digestibility, maintain forage quality longer than grases Helps other plants that grow by fertilizing the soil Legumes are not seeded at more than 1/3 of a grass/legume mixture by weight Non-ruminates Combine harvesting wheat, removing seed heads, leaving stems in the field Stalks are edible but do not contain many nutrients because the plants put the nutrients in the seeds Stems of plants like wheat, oats, and rye are often cut, dried I the sun, and baled for animal bedding (i.e. straw) Energy from highly digestible cereal grains Where does the protein come from? Legume plants are included in pastures to boost protein for monogastric animals Bean-type legumes are used in the diet, but the forage-type legumes Soybeans o Bean pods o Left in the field until very dry o Harvested and processed o Oil extracted and the rest of the seed is further processed for animal feed Forage-type legumes do not have beans (i.e. alfalfa and white clover) Silage Made when a plant is harvested when it still has considerable moisture Plant is chopped and put in a storage container/silo Microbial growth from bacteria in the warm, moist environment Bacteria die when they run out of oxygen, producing acids which preserve the plant material Plant is processed and used Can be made from many plants, but corn silage (the whole plant, not just the seed head) is widely used Popular amongst cattle