alimentary canal

1. 1 Comparative Digestive Physiology

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3. 3 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

4. 4 Primary Functions of the Digestive Tract Transport food � peristaltic contractions Digestion - reduce feed particles to molecules that can be absorbed into the blood mechanical breakdown by chewing chemical breakdown by HCl and digestive enzymes Absorption - allows nutrients to pass through membranes of GIT to the blood stream 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)

5. 5 Why do animals digest? Food not ingested in suitable state Physical nature of food determines gathering apparatus for uptake type of digestive system required

6. 6 Gastrointestinal Track (GIT) The major functions of the gastrointestinal tract are ingestion, digestion, absorption, and defecation

7. 7 Primitive Gastrointestinal Tract Found in monotremes (egg-laying mammals), insectivores (bats, shrews, moles), and dermopterans (colugos) Simple stomach, little or no division between small intestines and large intestines, large intestine simple, presence of caecum, non-sacculated colon

8. 8 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

9. 9 Mouth Functions Grasp food Taste Masticate food Mix with saliva

10. 10 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 need only to reduce the size of the particle Herbivores must chew continuously (40-50,000 times a day)

11. 11 Prehension Seizing and conveying feed to mouth Mechanisms vary with behavior and diet Forelimbs Primates, raccoon Snout Elephant, tapir Tongue Anteater, cow, sheep Lips Horse, sheep, rhinoceros

12. 12 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

13. 13 Mastication Physical reduction of feed Especially important in non-ruminant herbivores Adaptations Carnivores Large canines and incisors, tearing but little to no chewing activity Herbivores Specialized molars, lots of chewing and grinding Edentates (sloths, armadilloes, anteater) Relative toothlessness

14. 14 Teeth and Mastication Teeth are essential for proper chewing Distinguishing difference between carnivores and herbivores May regulate the amount of forage an herbivore is able to consume Problems with older animals

15. 15 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 Cellulase is found only in bacteria & some protozoans

16. 16 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

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21. 21 Teeth Specializations Carnivores Canine teeth highly developed and used for tearing Molars are pointed for bone crushing

22. 22 Teeth Specializations Omnivores grinding teeth patterns on posterior teeth (molars) piercing and ripping cusps on anterior teeth (incisors) Tongue - used to move feed to teeth

23. 23 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

24. 24 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 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)

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29. 29 Adaptations to Feed Sources Gastric capacity and structure Capacity is greatest in pregastric fermentors Stomachs act 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

30. 30 Adaptations to 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

31. 31 Digestive Tracts Stomach

32. 32 Digestive Enzymes Young animals produce little sucrase, maltase, amylase Ruminants produce no sucrase Adult pigs lack lactase Activity changes with age Lactase Sucrase, maltase

33. 33 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 turnover

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36. 36 Classification of Animals by Preferred Ingested Feedstuffs Carnivore � consume animal products dogs, cats komodo dragon, tigers, eagles, sharks, polar bear Herbivore � consume plant products cattle, sheep, goats, horses giant panda, gorilla, elephant, ostrich, green iguana, giraffe, American bison Omnivore � plant and(or) animal products pigs opossum, raccoon, blue jays, black bear, human

37. 37 Specialized Carnivores

38. 38 Specialized Herbivores

39. 39 Classification by Type of Digestion or Site of Digestion Monogastrics or non-ruminants Ruminants OR Pre-gastric fermentation (cranial) Post-gastric fermentation (caudal)

40. 40 Monogastric Animals Single, simple stomach structure Mostly carnivores and omnivores Very simple - mink, cat and dog Cecal digestion - horse, rabbit, elephant or rat Sacculated stomach - kangaroo

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42. 42 Ruminant Animals Ruminant � herbivores possessing multiple digestive tract compartments for feed breakdown before feed reaches the �true� stomach True ruminants - cattle, sheep, goats Pseudo-ruminants - camels, llamas, alpacas, vicunas

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45. 45 Classification of ruminants by feeding preference Classes of ruminants Concentrate selectors Intermediate feeders Roughage grazers

46. 46 Concentrate selecting species Properties Evolved early Small rumens Poorly developed omasums Large livers Limited ability to digest fiber Classes Fruit and forage selectors Very selective feeders Duikers, sunis Tree and shrub browsers Eat highly lignified plant tissues to extract cell solubles Deer, giraffes, kudus

47. 47 Intermediate feeding species Properties Seasonally adaptive Feeding preference Prefer browsing Moose, goats, elands Prefer grazing Sheep, impalas

48. 48 Roughage grazing species Properties Late evolved Larger rumens and longer retention times Less selective Digests fermentable cell wall carbohydrates Classes Fresh grass grazers Buffalo, cattle, gnus Roughage grazers Hartebeests, topis Dry region grazers Camels, antelope, oryxes

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56. 56 COW GIT Mouth contains dental pad, teeth, tongue and saliva saliva contains no salivary amylase Esophagus serves as passageway from mouth to stomach and from stomach to mouth Rumen - large fermentation vat that houses microorganisms. Reticulum "honeycomb" houses microorganisms catches hardware (ingested by animal) houses the opening to the omasum

57. 57 COW GIT Omasum "manyplies" full of folded tissue water absorption Abomasum true stomach pepsinHCl Small Intestine enzymatic digestion and absorption Functions of the small intestine: digestion of proteins, carbohydrates, and fats; absorption of the end products of digestion duodenum jejunum ileum Cecum - some microbial fermentation Large Intestine water absorption waste storage

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60. 60 GIT Capacity - Volume Carnivores stomach (70%) > 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

61. 61 Capacity of Digestive Tracts

62. 62 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

63. 63 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

64. 64 Disadvantages of pregastric fermentation Fermentation is inefficient Energy 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

65. 65 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

66. 66 Pregastric Fermenters

67. 67 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

68. 68 Postgastric Fermenters

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70. 70 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�

71. 71 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