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The Gastrointestinal Tract GIT

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allows animal to convert complex nutrients into forms that ... Avian (Poultry) Monogastrics (Swine) Mouth: proximal organ of GIT containing accessory organs ... – PowerPoint PPT presentation

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Title: The Gastrointestinal Tract GIT


1
The Gastrointestinal Tract (GIT)
  • AS 233

2
General Overview of Digestion
  • The GIT is vital
  • allows animal to convert complex nutrients into
    forms that can be absorbed and used
  • Most feeds are useless to the animal unless there
    is some form of alteration to the food

3
General Overview of Digestion
  • 1. Prehension
  • Seizing conveying of food to the mouth
  • i.e. Tongue, teeth, cleft lip, prehensile upper
    lip, dental pad
  • 2. Mastication
  • Movements of the jaw to crush the food particles
  • Herbivores - particles must be small enough to
    allow bacterial digestion to take place
  • - Cellulose

4
General Overview of Digestion
  • 3. Salivation
  • Secreting mixing saliva with food
  • Stimulated by
  • Feed Moisture
  • Physical form of feed
  • Scratch factor
  • Feeding period

5
Composition of Saliva
  • Water-moistens consumed food and aids in taste
    mechanisms
  • Mucin (glycoproteins)-lubrication for swallowing
  • Bicarbonate salts (Na)-act as buffer to regulate
    pH of stomach
  • Enzymes (some species)-salivary amylase begins
    CHO breakdown

6
Functions of Saliva
1. Lubrication 2. Bolus formation 3.
Buffering Fermentation products 4. Recycling of
nutrients Na, Cl, K, P, N (NPN)
  • 5. Enzymatic activity (Salivary amylase)
  • swine, birds
  • 6. Rinsing action
  • 7. Anti-frothing activity
  • esp. ruminants

7
Saliva Production
  • Horse 40 l/d (10.6 gal)
  • Cow 60 l/d (15.6 gal)
  • High-producing dairy cow
  • 120 - 200 l/d (31.7 - 52.8 gal)
  • Sheep 10 l/d (2.6 gal)
  • Sow 5-10 l/d (2.6 gal)

8
General Overview of Digestion
  • 4. Swallowing (Deglutition)
  • - Stimulated by the presence of a bolus in the
    back of the mouth

9
General Overview of Digestion
  • 5. Digestion Preparation / alteration of
    nutrients for absorption
  • 3 methods of digestion
  • 1. Mechanical modification of the physical
    form by chewing (mastication) or by the action of
    the muscular contractions of the GIT
  • 2. Chemical action of hydrochloric acid
    (HCl) in stomach or bile (secreted by liver) in
    small intestine
  • 3. Enzymatic action of enzymes secreted into
    small intestine
  • a. Amylase (CHO)
  • b. Proteases (protein)
  • c. Lipases (lipids)

10
General Overview of Digestion
  • 6. Absorption process by which digested
    nutrients cross the cellular lining (membrane) of
    GIT
  • 7. Metabolism Utilization of nutrients at the
    cellular level
  • Anabolic (building) and catabolic (breaking down)
    actions
  • Nutrient metabolism metabolic pathways are
    essentially the same in all animals
  • Some minor differences or alterations
  • Requirements type of food depends on the
    digestive tract

11
Classification of Digestive Systems
  • Physiological site of digestion
  • 1. Monogastrics
  • 2. Ruminants
  • Diet Selection
  • 1. Herbivores
  • Plants
  • 2. Carnivores
  • Animal tissue
  • 3. Omnivores
  • Both plants and animals

12
Monogastrics (Non-Ruminants)
  • Single compartmented stomach
  • Swine (Pig)
  • Equines (Horse)
  • Canine (Dog)
  • Feline (Cat)
  • Avian (Poultry)

13
Monogastrics (Swine)
  • Mouth proximal organ of GIT containing
    accessory organs
  • a. Lips prehension
  • b. Cheeks mastication and mixing
  • c. Teeth prehension and mastication

14
Monogastrics (Swine)
  • Mouth proximal organ of GIT containing
    accessory organs
  • d. Tongue prehension, mastication, mixing,
    taste, initiates deglutition (swallowing)
  • e. Salivary glands 3 glands that secrete
    saliva that contain amylase to initiate CHO
    digestion
  • 1. Parotid
  • 2. Submaxillary
  • 3. Sublingual

15
Monogastrics (Swine)
  • 2. Esophagus
  • Tube that allows bolus formed in the mouth to be
    transported (swallowed) into initial portion of
    GIT
  • Bolus moves via a series of muscular contractions
    called peristaltic waves
  • A valve (cardiac sphincter) is the junction b/w
    esophagus and stomach

16
Monogastrics (Swine)
  • Stomach hollow, pear-shaped, muscular digestive
    organ
  • FUNCTIONS
  • Storage of ingested feed
  • Muscular movements for food
  • Secretion of gastric juices
  • Material leaving stomach is called CHYME

17
Monogastric Stomach
Sphincter-ingesta passage to stomach
Nonglandular region
Mucus production
Sphincter- chyme passage into SI
Produces gastric secretions
Produces mucus and enzymes
18
Monogastric Stomach
  • Gastric Secretions
  • Acid (HCl)
  • Produced by parietal cells in fundic region
  • Kills bacteria
  • Activates digestive enzymes
  • Denatures (unfolds/aids digestion) of proteins
  • 2. Pepsinogen
  • Inactive proteolytic enzyme produced by chief
    cells in fundic region
  • Conversion to active enzyme pepsin requires HCl
  • Initiates protein digestion

19
Monogastric Stomach
  • Gastric Secretions
  • 3. Mucus
  • Produced by cardiac and pyloric cells
  • Protects stomach lining from acid and enzymes
  • Prevents autodigestion
  • Lubricant
  • 4. Rennin (chymosin)
  • Produced by fundic cells
  • Proteolytic enzyme
  • Young animals only-coagulates milk to slow
    passage rate

20
Monogastric Stomach
21
Monogastric (Swine)
  • 5. Small Intestine
  • 3 Sections
  • a. Duodenum
  • Pylorus of the stomach to the jejunum
  • Releases bile and pancreatic secretions
  • Proteolytic, Amylolytic Lipolytic activities
  • Active site of digestion
  • b. Jejunum
  • Middle portion
  • Active site of nutrient absorption
  • Most nutrients are absorbed at this point

22
Monogastric (Swine)
  • 5. Small Intestine
  • 3 Sections
  • c. Ileum
  • Terminal portion
  • Active site of nutrient absorption
  • Water, vitamins minerals
  • Some bacterial presence
  • Fermentation
  • ?The pH of the small intestine increases towards
    7.0 as food moves from the duodenum to the ileum

23
Monogastrics (Swine)
  • Large Intestine
  • 3 Sections
  • a. Cecum First section with little
    significance in pigs
  • A sac that is located at the beginning of the
    LI
  • Consuming high roughage diets increases the size
    and plays a major role in fermentation
  • Contains a microbial population similar to the
    rumen
  • Cellulolytic Hemicelluloytic bacteria

24
Monogastrics (Swine)
  • Large Intestine
  • 3 Sections
  • b. Colon Largest part of LI
  • Site of water and electrolyte re-absorption
  • water-soluble vitamins
  • Some fermentation
  • c. Rectum Terminal portion of LI

25
Functions of Large Intestine
  • 1. Water re-absorption and VFA absorption
  • 2. Microbial fermentation
  • 3. Secretion of some minerals
  • Na, Ca
  • No secretory glands (i.e. digestion)
  • Relies on microbes or secretions washed out of
    the SI
  • LI receives Sloughed cells, undigested food and
    microbial matter

26
GIT Morphology
27
Horse
  • 1. Mouth
  • Prehension via teeth, lips, and tongue
  • Saliva contains no enzyme
  • 2. Esophagus
  • One way peristaltic movementcannot regurgitate
  • 3. Stomach
  • Smaller than other speciesfeed small portions
    often
  • Less extensive muscular movement and ingesta
    arranges itself in layersprone to stomach
    digestive disorders

28
Horse
  • 4. Small Intestine
  • Similar to pig
  • No gallbladderdirect bile secretion into
    duodenum
  • Can not store bilecontinuous intake of food

29
Horse
  • 5. Large Intestine
  • 60 of GIT
  • 4 sections
  • 1. Cecum
  • 2. Large Colon
  • 3. Small Colon
  • 4. Rectum
  • Active bacterial population
  • Fermentation of CHO to VFA
  • Absorption of VFA
  • Bacterial synthesis of H2O soluble vitamins
  • Bacterial synthesis of protein

H2O absorption from intestinal contents
30
Avians (Poultry)
  • DIFFERENT from other Monogastrics
  • 1. Mouth
  • No teeth, rigid tongue
  • Poorly developed salivary glands
  • Saliva contains amylase
  • Beak is adapted for prehension and mastication

31
Avians
  • 2. Esophagus
  • Enlarged area called CROP
  • F(x) include
  • 1. Ingesta holding and moistening
  • 2. Location for breakdown of CHO by amylase
  • 3. Fermentation
  • 3. Proventriculus (Stomach)
  • F(x) include
  • 1. Release of HCl and pepsin (gastric juices)
  • 2. Ingesta passes through very quickly (14
    seconds)

32
Avians
  • 4. Gizzard (Ventriculus)
  • Muscular area with a hardened lining
  • Reduction particular size via
  • a. Muscular contractions every 20-30 seconds
  • b. By the action of grit (small stones or
    hard particles)
  • c. Action of HCl and pepsin secreted in
    proventriculus
  • 5. Small Intestine
  • Similar to other monogastrics

33
Avians
  • 6. Ceca and Large Intestine
  • Contain 2 ceca instead of 1 as in other
    monogastrics
  • LI is very short (2-4 in) and empties into CLOACA
    where fecal material will be voided via the VENT
  • F(x)
  • 1. Water resorption
  • 2. Fiber fermentation by bacteria
  • 3. H2O soluble vitamin synthesis by bacteria

At lower levels than other mammals
34
Ruminants
  • Cattle, Sheep, Deer, Elk, Bison
  • Multicompartmented Stomach
  • Make use of high fiber feedstuffs

35
Ruminant Forestomachs
Esophagus
Groove
Omasum
Pylorus
Rumen
Reticulum
Abomasum
36
Ruminants
  • 1. Mouth
  • No upper incisors
  • Lower teeth, lips, and tongue (prehension)
  • Teeth and upper dental pad (mastication)
  • Saliva contains no enzymes, but provides N, P,
    and Na for rumen microoganisms and is buffered to
    maintain appropriate pH in rumen

37
Ruminants
  • 2. Stomach
  • 4 compartments
  • a. Reticulum
  • Not completely separated from rumen-esophagus
    opening is common to both
  • Honeycomb walls that trap hardware to prevent
    travel to rest of GIT

38
Reticular Epithelia
39
Ruminants
  • 2. Stomach
  • 4 compartments
  • b. Rumen (paunch)anaerobic or no O2
  • Walls contain papillae
  • F(x)
  • 1. Storage
  • 2. Soaking
  • 3. Physical mixing and breakdown
  • 4. Bacterial fermentation (25-50 billion
    bacteria/mL fliud)

40
Rumen Fermentation
  • Bacterial H2O soluble vitamin and vitamin K
    synthesis
  • Bacterial AA synthesis by combining N (protein or
    NPN) carbon skeleton (CHO) to form own body
    protein
  • These bacteria are degraded to AA in SI
  • Fiber breakdown to VFA
  • Acetate, Propionate, Butyrate
  • VFA absorbed through rumen wallenergy source

41
Rumen papillae
42
Ruminants
  • 2. Stomach
  • 4 compartments
  • c. Omasum (manyplies)
  • Spherical organ with short, blunted papillae
  • F(x)
  • 1. Particle size reduction
  • 2. Water absorption

43
Ruminants
  • 2. Stomach
  • 4 compartments
  • d. Abomasum (true stomach)
  • First glandular portion of ruminant GIT
  • Secretes enzymes
  • Gland regions similar to those of monogastrics
  • 3. Small and Large Intestines
  • Similar to monogastrics

44
Peculiarities to Ruminants
  • Esophageal (or reticular) groove
  • A passageway which can close to allow milk to go
    directly from the esophagus to the omasum
  • bypasses reticulorumen bacterial fermentation
  • Not functional in older animals

45
Peculiarities to Ruminants
  • Rumination
  • Allows animal to forage and eat food rapidly, and
    then store for later digestion
  • Regurgitation, remastication, relubricating,
    reswallowing
  • Mainly roughage and liquid
  • Cattle spend 8 hrs/day ruminating

46
Peculiarities to Ruminants
  • Eructation
  • Microbial fermentation producers large amounts of
    gas (carbon dioxide methane)
  • Esophagus dilates cow belches
  • Bloat when gases can not escape
  • Stable froth or foam formed in rumen
  • Prevent foam or break it up
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