Comparative-Digestive-Physiology-(mod)-大学动物营养学.ppt

Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Comparative Digestive Physiology,Why Do Animals Digest?,Food not ingested in suitable state,Physical nature of food determined by:,gathering apparatus for uptake,type of digestive system,Primary Functions of the Digestive Tract,Transport food,peristaltic contractions,Digestion,Mechanical breakdown,Chemical breakdown,Absorption,Passive diffusion and active transport,Synthesis,-true protein,FA,starch,vitamins,Excretion,elimination of waste products,Via bile(toxins,microbes etc),Via rectum(Ca,Mg,P),Regions of Alimentary Canal,Foregut functions,Ingestion and storage of feeds,Midgut functions,Mechanical,chemical&enzymatic digestion of feed,Nutrient absorption,Hindgut functions,Water&ion re-absorption,Formation,storage,excretion of feces,Species-Dependent Nutritional Adaptations,Includes involvement of:,Teeth,Jaws and jaw musculature,Alimentary canal,Stomach-May be simple or become sacculated to compartmentalize functions for prolonged storage of feed and utilization of bacterial fermentation(langures and ruminants),May also become voluminous for storage of large amounts of feed(vampire bats),Large intestine-varies substantially in length,compartmentalization,and complexity among species,Mouth,Functions,Grasp food,Taste,Masticate food,Mix with saliva,Digestion in the Mouth,Prehension,Bringing the food to the mouth,Upper limbs,head,beak,claws,mouth,teeth and lips,Mastication or chewing,To crush the food,increase surface area and allow enzymes to act on molecules,Carnivores only to reduce the size of the particle to a size small enough to swallow,Herbivores must chew continuously(40-50,000 times a day)to increase surface area,Prehension,Domestic mammals use lips,teeth and tongue,Relative importance varies by species,Horses,lips when eating from manger,teeth when grazing,Cows and sheep have limited use of lips,Use long rough tongue to grasp forage,Pigs use snout to root in ground and pointed lower lip to convey feed into mouth,Birds use beak and tongue,Drinking varies as well,Most mammals use suction,Dogs and cats use tongue to form ladle,The Importance of Prehension in Diet Formulation,White Rhino(“wijd”=wide),Squared off upper lip used to“crop”grass,Grazes on savannah,Black Rhino,Prehensile upper lip for browsing,Consumes bushes and shrubs in forest,Morphological Adaptations for Herbivory,All related to finding,ingesting,masticating,and digesting plant cell walls,Dental adaptations for,herbivory,include changes to incisors,molar,occlusal,surfaces,&,masseter,Solution for digestive problems is to provide a place in digestive tract for,anaerobic,bacteria&,protozoans,(,microflora,)to colonize,Teeth Specializations,Carnivores,Canine teeth highly developed and used for tearing,Molars are pointed for bone crushing,Jaw&Teeth Specializations,Non-ruminant herbivores(horse),Incisors for nipping,molars slightly angled,jaws move circularly(vertical and lateral),Ruminants,No upper incisors,have dental pad,molars allow only lateral movements,Different classes-roughage eaters,transition types,selective eaters all differ in tongue mobility and cleft palate,Jaw Muscles and Mastication,Temporalis muscle-develops maximum force on anterior portion of jaw(largest muscle in carnivores and smallest muscle in herbivores),Masseter and medial pterogoid-maximum force for crushing and grinding,Lateral pterogoid-allows lateral movement which is important for grinding(highly important in herbivores,but carnivores and many omnivores have almost no lateral movement of jaws),Salivation,Quantity and composition of saliva varies considerably between species,Quantity related to level of chewing activity,Amount of secretion,Dogsminimal(lubrication,no enzymes),Sheep3-10 liters/d,Horse10-12 liters/d,Cattle130-180 liters/d,Esophagus,Species adaptations,Ability to control peristaltic contractions,Reverse peristalsis,Amount and location of skeletal muscle,Regurgitation vs.vomiting,Foregut in Birds,Crop,Bottom of the esophagus forms a sac called crop,Stores undigested food.,Birds with crop gorge when food is available,store it in crop,and slowly digest it later,Digestive Adaptations to Varying Feed Sources,Gastric capacity and structure,Capacity,is,greatest,in,pregastric,fermentors,Stomach acts as reservoir,Small stomach in carnivores is related to high nutrient density of the diet,Distribution and composition of epithelial lining varies between species and dietary adaptations,Digestive Adaptations to Varying Feed Sources,Intestinal length and functions,Small intestine,Less variable among species than stomach and hind gut,but generally shorter in carnivores than in herbivores,Large intestine,Importance of hind gut fermentation dictates variation in structure and size,Some hind gut fermentation occurs in most species,Adaptations of the Digestive Tracts,Rule,Size=Function,Stomach,Small Intestine,Cecum,Large Intestine,Utilizing Cellulose,Advantages,Ultra-abundant in the environment,Easily obtained no need to“hunt”plants,Plant cell walls&fiber high in energy,Disadvantages,Indigestible by mammalian digestive enzymes,Cellu,lase,is found only in bacteria&some protozoans,Fermentative Digestion,All mammals have some fermentative capacity that allows for utilization of ingested fiber,The comparative importance of fermentation is related to the fraction of total digesta contained in fermentative compartments of the gastrointestinal(GI)tract,Advantages of Pregastric Fermentation,Make better use of alternative nutrients,Cellulose,Nonprotein nitrogen,Ability to detoxify some poisonous compounds,Oxalates,cyanide,alkaloids,More effective use of fermentation end-products,Volatile fatty acids,microbial protein,B vitamins,Allows wild animals to eat and run,Disadvantages of Pregastric Fermentation,Fermentation is inefficientEnergy,Loss%of total caloric value,Methane 5-8,Heat of fermentation 5-6,Relative efficiency is dependent on the diet NDF,Protein,Some ammonia resulting from microbial degradation will be absorbed and excreted,20%of the nitrogen in microbes is in the form of nucleic acids,Disadvantages of Pregastric Fermentation,Ruminants are susceptible to ketosis,Ruminants are susceptible to toxins produced by rumen microbes,Nitrates to nitrites,Urea to ammonia,Nonstructural carbohydrates to lactic acid,Tryptophan to 3-methyl indole,Isoflavonoid estrogens to estrogen coumestans,Pregastric Fermenters,Class,Species,Dietary habit,Ruminants,Cattle,sheep,Deer,antelope,camel,Grazing herbivores,Selective herbivores,including folivores and frugivores,Nonruminants,Colobine monkey,hamster,vole,Kangaroo,hippo,Hoatzin,Selective herbivores,Grazing and selective herbivores,Folivore,Postgastric Fermentors,Cecal fermentors,Mainly rodents,rabbits and other small herbivores,Often associated with coprophagy,Colonic fermentors,Includes true herbivores(e.g.,horse),omnivores(e.g.,pig and human),and carnivores(e.g.,cat and dog),Horse has some expanded cecal fermentation in addition to greatly expanded colonic fermentation,Degree of colonic sacculation is related to importance of fiber digestion and fermentative capacity,Postgastric Fermenters,Class,Species,Dietary habit,Cecal digesters,Capybara,Rabbit,Rat,mouse,Grazer,Selective herbivores,Omnivores,Colonic digesters,Sacculated,Unsacculated,Elephant,horse,zebra,New World monkeys,Pig,human,Panda,Dog,cat,Grazers,Folivores,Omnivores,Herbivores,Carnivore,Foregut vs.Hindgut Fermentation,Foregut,More efficient per unit volume of food,Slower digestive process,Animal may starve with a full belly,Size restricted,Hindgut,More efficient relative to time,Faster turnoverFeeding Habits of Mammals&Taxonomic Distribution,Feeding Habit,Number of Orders,Percent of Species,Herbivory,10 40,Frugivory,Graniv,.,Nectivory,5 4,Carnivory,4 12,Planktonivory,?(Krill feeders)2 SI=LI(15%),GIT surface/body surface:0.6:1,Omnivores,stomach=SI=LI(33%),GIT surface/body surface:intermediate,Herbivores,Ruminants,stomach(70%)SI(20%)LI(10%),GIT surface/body surface:3:1,Non-ruminants,stomach(10%)SI(30%)LI(60%),GIT surface/body surface:2:1,GIT Classifications-Dog,Monogastric,carnivore with limited post-gastric fermentation,Simple stomach,not capable of effective utilization of forage-based(high fiber)diets,Unable to digest some of the substances in grains,fruits and vegetables,Similar to cat,GIT Classifications-Pig,Monogastric,omnivore with limited post-gastric fermentation,Simple stomach,not capable of effective utilization of forage-based(high fiber)diets,Unable to digest some of the substances in grains,fruits and vegetables,Similar to human,Pig,_,Large Intestine,(16,2 gal),Cecum,(10”,0.5 gal),Small intestine,(60,2.5 gal),Stomach,(2 gal),Esophagus,Mouth,Human Digestive Tract,Rat,GIT Classifications-Kangaroo,Monogastric,omnivore with limited pre-gastric fermentation,Sacculated,stomach,capable,of utilization of forage-based(high fiber)diets,Able to digest some of the substances in grains,fruits and vegetables,GIT Classifications-Horse,Monogastric,herbivore with extensive post-gastric fermentation,Simple stomach incapable of utilization of forage-based(high fiber)diets,Extensive fermentation after primary sites of digestion and absorption,Horse,_,Large Colon,(12,19 gal),Cecum,(4,8 gal),Small intestine,(70,12 gal),Stomach(3.5 gal),Esophagus,Mouth,Small Colon(12,3 gal),GIT Classifications-Sheep,Ruminant herbivore with extensive pre-gastric fermentation,Highly developed,sacculated,stomach capable of extensive and effective utilization of forage-based(high fiber)diets,Extensive fermentation before primary sites of digestion and absorption,Similar to cattle and goats,Cow,_,Small intestine,(150,16 gal),Abomasum,(glandular),(5 gal),Omasum,(4 gal),Cecum,(3,3 gal),Esophagus,Mouth,Rumen(paunch),(43 gal),Reticulum,(honeycomb),(2.5 gal),Large intestine,(33,8 gal),GIT Classifications,Avian is modified,monogastric,Beaks replace lips and teeth,Crop(enlarged area of esophagus)stores and softens feed prior to entering stomach,Proventriculus,glandular stomach,Gizzard muscular part of stomach,Branched,cecum,postgastric,fermentation,Cloaca,both fecal and urinary waste,Uric acid rather than urea(insoluble),Chicken,Beak,Esophagus,Crop(2”),Small Intestine(55”),Proventriculus,Gizzard(2”),Pancreas,Ceca(7”),Large Intestine(4”),Cloaca,Feeding Behaviors,Impact feed choices,Neophobia(avoidance of new feed sources),Contact testing(based on taste and other sensory information collected in mouth)prior to swallowing,Early introduction of a variety of feeds limits this problem,Chimpanzees select feeds based on easily digestible carbohydrate content(sugars and starches)rather than fat or protein content,Grazers and browser select early growth grasses and plants vs.mature growth,In confinement feeding situations,grazers consume concentrates first and then forages in ration based on particle size(basis for creating“total mixed rations”),Feeding Behaviors,Impact feed intake(avoiding under-and over-consumption of feed),Hiding feed in bear exhibit encourages search and gather behaviors,limiting intake and reducing the stress of captivity,Predator behavior towards“prey”meals vs.“bowl”meals,Grazing animals prefer to eat forage at ground level rather than in elevated feed bunks,