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First year semester 2 > GI ruminants > Flashcards

GI ruminants Flashcards

1
Q

Definition of: Deglutiton

A

Swallowing

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2
Q

Definition of: Mastication

A

Chewing

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3
Q

Definition of: Regurgitation

A

• Passive transfer of stomach contents to oral cavity for re-mastication

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4
Q

Definition of: Re- mastication

A

• Additional chewing of fibrous material that has been regurgitated

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5
Q

Definition of: Rumination

A

• The entire process of regurgitation, re-mastication and re-deglutition (chewing the cud)

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6
Q

Definition of: Eructation

A

• Expulsion of gas from the stomach (belching / burping)

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7
Q

Definition of: Peristalsis

A

• Aboral movement of food down the GI tract by controlled contraction / relaxation of associated muscles

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8
Q

Definition of: Reverse peristalsis (anti peristalsis)

A

Aboral movement of food towards the mouth instead of away from the mouth

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9
Q

Ruminant stomach:

A
  1. Ruminant stomach adapted for fermentation of roughage / fibre
  2. 4 componetns. 3 parts = fermentation. 4th = stomach
  3. Enlargement of the oesophageal area = fore-stomach (3 compartments)
    • Reticulum
    • Rumen
    • Omasum
  4. Fourth compartment equivalent to simple stomach = Abomasum
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10
Q

Reticulum

A
  • Inner surface raised into ridges (honey comb arrangement)
  • Strongly muscled wall (smooth muscle)
  • Capacity = 10-20 litres
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11
Q

RUMEN

A
  • Longitudinal groove / pillar divides it into dorsal & ventral sac
  • Coronary (vertical) grooves / pillars define caudo-dorsal / ventral blind sacs = slow fermentation
  • Walls contain smooth muscle for contraction
  • Papillae (especially caudo-dorsal blind / ventral sacs) – SA inc
  • Absorption of (huge quantities of) H2O, VFAs, ions
  • Papillae increase surface area for absorption
  • No smooth muscle (immobile)
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12
Q

What compartments make up the fore stomach?

A
  1. reticulum
  2. rumen
  3. omasum
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13
Q

Why are reticulum and rumen often grouped together?

A
  1. functionally do same thing

2. very heavily involved with one another when it comes to motility

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14
Q

What is the nervous contribution to the rumen?

A
  1. regulate contraction via short reflexes of enteric nervous system
  2. modulated by long reflexes via vagus nerve
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15
Q

Histology of forestomach

A
  1. Stratified squamous epithelium
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16
Q

ABOMASUM

A
  1. “true” stomach
  2. columnar epithelium with glands that secrete: HCL, pepsinogen, rennin (in young ruminants)
  3. Receives small quantity of fermented material from omasum that contains lot of bacteria the abosasum can digest. REst = into small intestine
  4. pH slightly higher than simple stomach (2) of about 4 due to alkalinity of fermentation fluid. Still low enough to kill ruminal microbes for digestion
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17
Q

Why is renin secreted into the abomasum of young animals?

A
  1. Renin precipitates/ coagulates casin to stay in abomasum longer so pepsin more change to digest more efficiently
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18
Q

How are digestive components distributed in rumen reticulum?

A
  1. Distribution of forage in rumino-reticulum of grazers depends on density
  2. Very dense particles such as stones / wire fall straight into reticulum where they usually remain
  3. Density of other particles depends largely on associated gas from their fermentation
  4. Large particles (eg long grass / hay / straw) “float” in bottom of dorsal sac at level of oesophagus
  5. More dense particles sink into reticulum / cranio-dorsal blind sac / ventral sac – for absorption
  6. Gas from fermentation (CO2 / CH4 / H2S / H2 / N2) collects at top of dorsal sac
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19
Q

Rumino-reticulum motility

A
  1. 3 types of contractions
  2. Primary c
  3. Secondary c
  4. Rumination c
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20
Q

Talk about primary contractions of the rumino-reticulum

A
  1. Main one
  2. occur pretty continuously
  3. higher frequency when eating, lower when ruminating, very low but still occur when not eating
  4. point = move things around and mix up
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21
Q

What do the number of contractions tell us about a ruminant?

What is the “normal” number?

A

How healthy it is
Number:
1. Primary (mixing of contents)
• 5-8 strong contractions / 5 mins during eating
• 4-5 contractions / 5 mins during rumination
• 0-1 weak contractions / 5 mins during fasting (sleeping)
2. Secondary (eructation)
• Occur after every 2-3 primary contractions
3. Rumination (regurgitation / remastication / reswallowing)

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22
Q

Secondary contractions

A

POINT = get rid of waste gas
fairly frequently
gas out of front end

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23
Q

Rumination contractions

A
  1. contractions required to move material from rumen up oesophagus to mouth
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24
Q

Go through contractions from first reticular contraction

A
  1. primary: First reticular contraction (partial) moves coarse material towards central/ dorsal rumen
  2. Primary: Second reticular contraction (complete) moves material into:
    a) cranial blind sac.
    b) FERMENTED material = through reticulo-omasal orifice into omasum
  3. primary: cranial blind sac contraction = moderately fermented material into dorsal sac. Well fermented material passes into reticulum
  4. primary: dorsal sac contraction = backwards contraction. Overall circular movement of contents in dorsal sac. some gas exchange with ventral sac
  5. Primary: Ventral sac contraction = backwards contraction
    overall circular movement of contents. Some exchang with dorsal sac. Well fermented mat = into cranial blind sac
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25
Q

Contractions during rumination

A
  1. Rumination occurs when coarse material stimulates oesophageal opening
  2. An extra reticular contraction precedes the normal biphasic reticular contractions
  3. Normal primary contractions then follow
  4. Rumination occurs 6-10 times per day requiring approx 60 mins per kg roughage eaten
  5. Rumination generally occurs at night and during afternoon rest period
  6. Ruminants NEED to ruminate
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26
Q

Rumination: from mouth

A
  1. Newly swallowed material forced into dorsal sac and replaced by partially fermented material
  2. Thorax expands generating negative pressure in oesophagus
  3. Lower oesophageal sphincter opens
  4. Diaphragmatic muscle contractions forces material into oesophagus
  5. Cf abdominal contractions in vomiting
  6. Reverse peristaltic oesophageal contractions convey material to oral cavity
  7. Liquid immediately re-swallowed
  8. Rest of material re-chewed with additional salivary secretion & re-swallowed
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27
Q

Eructaiton contractions

A
  • 2000-4000 litres gas from fermentation per day in dorsal sac
  • Occurs after every 2-3 primary contractions
  • Oesophageal opening usually below level of gas hence gas can’t escape during rumination
  • Eructation can’t occur with animal lying on side
  • Makes general anaesthesia / surgery complicated
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28
Q

Eructation

A
  • Primary contractions occur as normal
  • Caudo-dorsal blind sac contracts forward displacing contents into relaxed cranial blind sac and ventral sac
  • Dorsal sac continues contracting and moves gas at top of dorsal sac to oesophageal opening
  • Increased negative pressure in thorax causes oesophagus to expand
  • Cardiac sphincter opens and gas escapes into oesophagus, reverse peristalsis carrying gas to oral cavity
  • Some escapes via mouth but most inhaled (hence odorous substances sometimes getting into the milk)
  • Ventral sac contraction allows gas collecting in caudo-ventral blind sac to escape to the top of the dorsal sac of the rumen
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29
Q

What causes bloat?

A
  • Failure to eructate results in “bloat”
  • Complete oesophageal obstruction eg potato
  • Partial oesophageal obstruction eg neck abscess / tumour
  • Fresh clover results in small bubbles that fail to coalesce, form a foam that doesn’t collect in the dorsal sac and hence can’t be eructated (“frothy bloat”)
  • Increased ruminal pressure causes respiratory & cardiac distress
  • Stretching of rumen reduces / stops ruminal contractions
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30
Q

How is the forestomach motility regulated?

A
  • Occurs mainly by autonomic long reflexes
  • Both afferent (sensory) & efferent (motor) fibres travel in vagus
  • Vago-vagal reflex both vagal routes
  • 2 types of sensory cell containing:
  • Tension receptors – moderate stretching
  • Both mechano (high stretching) & chemo-receptors
31
Q

How is motility stimulated?

A
  • Tension receptor containing cells
  • In series with smooth muscle cells & sensitive to moderate stretch of rumen walls
  • Concentrated around oesophageal opening, oesophageal groove, reticulum wall, rumen pillars & cranio-dorsal blind sac wall
  • INCREASE motility
32
Q

How is motility inhibited?

A
  • Mechano- & Chemo-receptor containing cells
  • Sensitive to severe stretch, pH, osmolarity & VFA concentration
  • Located in basal layer of rumen epithelium (epithelial receptors)
  • DECREASE motility (so animal metabolism can catch up)
33
Q

Describe the development of the forestomach

A
  • At birth abomasum developed but not fore-stomach
  • Fore-stomach develops when starts to eat more roughage at about 2-3 weeks old
  • Micro-organisms for fermentation develop too but still dependant on milk for nutrition
  • Received mainly from mother by licking hence why bonding so important
  • Milk bypasses fermentation chamber via oesophageal groove
34
Q

What is the oesophageal groove

A

muscular structure at the lower end of the esophagus that, when closed, forms a tube allowing milk to go directly into the abomasum. (This prevents milk from being fermented or soured by the ruminal microorganisms)

  1. formed by posture of calf (lifting head to suckle)
  2. unconditioned reflex
  3. closes in diff species at diff ages when weaned
35
Q

brief structure and what happens when drinks

A
  • Groove with lips that runs from oesophagus to reticulo-omasal orifice
  • When animal sucks warm milk reflex causes lips to curl over forming a tube
  • Cold milk prevents complete curling over and can then spill into reticulo-rumen
36
Q

What if bucket fed or milk intake exceeds capacity of tube ?

A
  • Groove with lips that runs from oesophagus to reticulo-omasal orifice
  • When animal sucks warm milk reflex causes lips to curl over forming a tube
  • Cold milk prevents complete curling over and can then spill into reticulo-rumen
37
Q

What stimulates closure of osophageal groove/ reticular groove or ventricular groove

A
  • Sucking and chemoreceptors in pharynx sensitive to milk compounds cause reflex closure of groove
  • Can also be stimulated by certain salt solutions used to prepare oral medication that bypasses fermentation chamber
38
Q

Why deos fermentation occur?

A
  • Most plant material cannot be digested by mammalian enzymes
  • Requires microbial fermentation = chemical breakdown of a substance by micro-organisms under anaerobic conditions
39
Q

• Rumino-reticulum

A
  • Physiologically function together
  • Provide environment for microbial population
  • Delay gut-transit to allow sufficient time for fermentation
  • Lignified roughage retained longer than succulent herbage
40
Q

What does the bacteria Amylolytic do?

A

ferments hydrolysable carbohydrate

life span 0.5 hrs

41
Q

What does the bacteria Cellulolytic do?

A

ferments non-hydrolysable carbohydrate

2. life span 18 hrs

42
Q

What is an important condition and why?

A
  1. ANAEROBIC
    • Under aerobic conditions food substances would be completely broken down to CO2 & H2O which don’t provide energy to the host
    • Anaerobic conditions prevent total degradation resulting in metabolites that host can use for energy
43
Q

What is the name for anaerobic bacteria that use O2

A

facultative anaerobes
Adhere to luminal surface
• Remove all O2 thereby rendering environment anaerobic

44
Q

Describe microorganism set up in reticulum/rumen

A
  • Most are bacteria
  • Protozoa much larger therefore contribute almost equally to microbial mass
  • Environment physically / chemically regulated
  • Density and competitive balance between micro-organisms remains stable PROVIDED feeding pattern is stable
  • Too rapid change in ingested food will upset balance
45
Q

Microorganisms in the rumen/reticulum

A
  1. BActeria = amylolytic, cellulolytic proteolytic, methanogenic, lactate-utilisers
  2. protozoa
  3. fungi
46
Q

How is the mcirobes established when the newly born gut is sterile?

A

• Microbes must be ingested (mostly from mother initially)
• environmental microbes ingested,
ruminal ones establish (competative advantage)
• Due to rumination mother’s oral cavity contains representative populations of ruminal microbes
• Transferred to young by licking / grooming
• This bonding therefore essential to establishing ruminal microbial population

47
Q

What would ahppen if the neonate was isolate?

A
  1. gradually establish bacterial but not protozoal populations (protazoa can live long in open environment)
  2. fermentation will develop just not as efficient
48
Q

How are bacteria classified?

A

on basis of nutrients metabolised

49
Q

Protozoa

A
  • Mostly ciliates, much larger than bacteria (can engulf bacteria)
  • Retained longer in rumen by adhering to large feed particles
  • Produce VFAs, lactate, CO2 & H2
  • Proliferate with high starch diets, reduced with high fibre diets
  • Store glucose as glycogen
  • This glucose can be recovered when protozoa pass into small intestine and are digested
  • Ruminants can survive without protozoa but fermentation much more efficient in their presence
50
Q

Fungi

A
  • Represent small proportion of microbial population
  • Reproduce by free-swimming flagellated spores
  • Can only break down lignin aerobically
  • Rumen under anaerobic conditions!
  • Lignin indigestible but presumed that spores attach to lignin and split it apart by hyphae thereby rendering it susceptible to celluloytic digestion
  • Proliferate with diets high in lignin (e.g. straw)
51
Q

RUMEN ACIDOSIS

A
  • Consumption of increased levels of hydrolysable CHO
  • VFAs ↑↑ / pH ↓↓ (amylolytic survive, cellulolytic don’t protozoa die LP inc)
  • If pH decreases too much acid-resistant lactate producers proliferate at expense of lactate-utilisers
  • Lactate poorly absorbed cf VFAs
  • Too low pH injures rumen epithelium
  • Water enters rumen by osmosis inc in solutes but now can’t reabsorb water = blood vol dec
  • Dehydration / hypovolaemic shock ensues
  • Treated by iv alkaline fluids (corrects both dehydration and acidosis)
  • Can be prevented by introducing levels of hCHO gradually (over 3-4 weeks) to enable lactate-utilisers (cant work at low pH) to increase in level with lactate producers
52
Q

Why is it important not to change the diet of a ruminant rapidly?

A
  1. important not to disturb the ratio of diff families of microorgansims? bac, protozoa and fungi
  2. Quickly = upsets one populaiton at expense of other
  3. usually myolytic (rapid fermenters) tend to be more resistent
  4. inc rate of fermentation = produce VFA at faster rate than designed = decrease pH
53
Q

Role of amylolytic bacteria

A
  1. break down alpha glycosidic bonds = hydrolysable carbo
  2. survive low pH
  3. proliferate v quickly = can get out of hand if upset environ
54
Q

Role of cellulolytic bacteria

A
  1. break down non hydrolysable carbo (beta glycosidic bonds)

2. can’t survive at low pH = die if envir disturbed

55
Q

Role of proteolytic bacteria

A
  1. fermentation of protein and then use for themselves

2. protein –> peptides –> aa –> VFA and NH4+

56
Q

Role of methanogenic bacteria

A

CO2 into CH4

small proportion

57
Q

Role of lactate utilisers

A

lactate –> propionate

die at low pH

58
Q

as protein is digested what is produces?

As CHO digested what produced?

A
  1. NH4+
  2. VFA
  3. pH DOWN
59
Q

Homeostasis of rumen

A
  1. digestion = NH4+ and VFA inc
  2. pH dec which inc osmoregularity
  3. water enters rumen by osmosis
  4. NH4+ taken up by microbes, VFA absorbed by host
  5. Increased rumination/ HCO3- from saliva and blood
  6. osmoregulatily dec, pH inc
  7. water reabsorbed
60
Q

Ruminant metabolism

A
  1. V efficient, only 10% feed energy lost (mostly via CH4 production)
  2. Rumen microbes can degrade many toxins before their absorption cf simple stomached animals
    • Foxglove leaves (digitalis)
    • Ragwort (horses v. susceptible
  3. Homeostatic envir must be maintained
61
Q

What is the rate of fermentation in the ruminant dependent on?

A
  1. Type of feedstuff
    • Starch fermented more rapidly than fibre
  2. Volume of feedstuff
  3. Microbial balance
    • Amylolytic bacteria ferment faster than celluloytic
62
Q

How is propionate formed?

A
  1. via 2 metabollic pathways
    • Via anaerobic glycolysis of pyruvate
    • From lactate
  2. diet high in starch enable proliferation of lactate utilisers so inc overall VFA production :. inc relative propionate production
63
Q

Methane production

A
  1. need to be produced
  2. for glycolysis to occur need to reduce NAD+ to NADH
  3. Methane producers reduce CO2 to methane via oxidation of NADH back to NAD+
  4. regenerated NAD+ and recyled H+ ions thereby help maintain ideal rumen pH
64
Q

Methane production

A
  1. need to be produced
  2. for glycolysis to occur need to reduce NAD+ to NADH
  3. Methane producers reduce CO2 to methane via oxidation of NADH back to NAD+
  4. regenerated NAD+ and recycled H+ ions thereby help maintain ideal rumen pH
65
Q

How does a ruminant metabolise fat

A
  1. diets modified to inc fat especially in dairy cattle

2. hydrolysed and fermented to VFAs

66
Q

How does a ruminant metabolise protein

A
  1. again not directly availabel to hsot but to bacteria
  2. Degraded into peptides, AA, Nh3 and organis acids and branches fatty acids (stimulate growth of cellulotic bacteria)
  3. for microbes to proliferate = high rate of protein synthesis
67
Q

Where do microbes get nitrogen from for protein synthesis?

A
  1. Most = inorganic nitrogen

2. also non protein nitrogen in food and additives (urea)

68
Q

Metabolism of NPN

- what are NPN

A
  • NPN consist of amides, amines, peptides, amino acids, nucleic acids, urea, nitrates & ammonium ions
  • Ruminants (cf other simple-stomached animals) can utilise NPN for protein synthesis (via microbes)
  • NPN → NH3 → amino acids → protein
  • Microbial protein digested in stomach / small intestine as in simple-stomached animals
  • NPN essential for healthy microbial population
  • Grass / grain contains 5-15% NPN
  • Silage (due to microbial fermentation) contains 70% NPN
69
Q

Why silage fed? esp dairy cows

A
  1. partly fermented so contains 70% NPN vs grass 5-15%
70
Q

What lactation requires

A
  1. dairy dcows require more than microbial protein
  2. urea often added to inc NPN to inc microbial population
  3. inc microbial proliferation = inc VFA to host. Molasses = good source
  4. Xtra by pass protein added to diets escape fermentation as poorly soluble and pass into abomasum. small I for digestion
71
Q

What is unique to ruminants with surplus protein?

A
  1. recycled into urea by liver and secreted in saliva
72
Q

Waht is absorption?

What enhances absorption in ruminant?

A
  1. selective transfer of useful nutrients into the hosts blood stream
  2. • Reticulo-rumen enhances this by papillae that increase surface area for absorption
    • Papillae most dense in parts of rumen responsible for absorption (ventral sac & cranial / caudo-dorsal blind sacs). absorbs principially VFA
73
Q

Omasal absorption

A

smaller component – regulates passage and mops up water
• Surface area increased by leaves / papillae
• Fermentation continues in omasum
• Absorption of ~10% total VFA leaving only ~10% passing into abomasum
• Water (10-15%) / Na+ (25%) also absorbed
• Ingesta therefore more solid than in rumen
• Contains less HCO3- therefore abomasum needs to secrete less H+
• Some rumen material passes straight into abomasum via omasal canal

First year semester 2 (50 decks)

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