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The rumen (anatomy, microbiology, function, diseases) Flashcards

1
Q

Name the digestive sacs of the ruminant

A
  • Rumen
  • Reticulum
  • Omasum
  • Abomasum (true stomach)
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2
Q

What is the function of the rumen-reticulum?

A
  • Mammals unable to digest beta-linked polysaccharides e.g. cellulose
  • Rumen reticulum (and omasum) allows utilisation of micro-organisms to assist digestion
  • Rumen is large fermentation vessel
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3
Q

Give a brief overview of the forestomachs of the ruminant

A
  • Rumen, reticulum, omasum
  • Derived from gastric spindle
  • Lined by stritified keratinied epithelium
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4
Q

Give a brief overview of the ruminant abomasum

A
  • “True stomach”
  • Analogous to stomach of monogastrics
  • Acid producing
  • Lined by simple columnar epithelium with occasional goblet cells
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5
Q

Where is the rumen-reticulum located?

A

Takes up most of left side of abdominal wall

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6
Q

Name the sacs of the rumen (in order, starting at the top going clockwise)

A
  • Dorsal sac
  • Dorso-caudal (blind) sac
  • Ventro-caudal (blind) sac
  • Ventral sac
  • Cranio-dorsal (blind) sac
    (At very front have reticulum, kind of like sac of rumen)
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7
Q

Where are the omasum and abomasum located?

A

On the right side, omasum more cranial

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8
Q

Describe the oesophagus of the ruminant

A
  • Large (diameter up to 6cm)
  • Distensible
  • Striated m. along whole length
  • Mucosa insensitive
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9
Q

What is “chock” and where does it comonly occur?

A
  • Obstruction of oesophagus

- Commonly close to pharynx and at thoracic inlet

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10
Q

Describe the conditions in the rumen-reticulum and why this is important

A
  • Large volume
  • Warm (close to body temp)
  • Moist
  • Anaerobic
  • pH ~6.5
  • Environment suitable for range of microorganisms that digest and degrade plant material
  • Particularly cellulose and hemicellulose
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11
Q

What are the products of fermentation in the rumen?

A
  • Volatile fatty acids (acetate, butyrate, proprionate)
  • CO2
  • Methane
  • Fibrous feedstuffs remain long enough for complex carb digestions
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12
Q

How frequently do rumen- reticulo contractions occur?

A

~3 every 2 mins

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13
Q

What is the purpose of the rumen-reticulo contractions?

A
  • Stire, redistribute and mechanically grind food

- Partitions fibre for re-chewing

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14
Q

What are the layers of digestive material found in the rumen-reticulum? (top to bottom)

A
  • Gas
  • Fibre mat (thickest fibre material)
  • Intermediate zone
  • Liquid zone
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15
Q

What are the fates of the rumen-reticulo zones?

A
  • Fibre mat selected for remastication

- Liquid zone moves forward into omasum and abomasum

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16
Q

What is the function of the cycling movement in the rumen-reticulum?

A
  • Stirs and redistributes contents

- Maximises efficiency of breakdown, eructation, remastication and forward movement of digested food

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17
Q

What are the 2 types of cycles found in the rumen-reticulum?

A
  • Primary (A) cycles

- Secondary (B) cycles

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18
Q

Describe the primary (A) cycles within the rumen-reticulum

A
  • Mixing
  • every 1-2 mins
  • Diphasic contraction of reticulum - monophasic contractino of dorsal sac then ventral sac
    Contraction wave moves in cranial to caudal direction
  • Mix ingesta and aids flow of liquid layer into omasum
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19
Q

Describe the secondary (B) cycles within the rumen-reticulum

A
  • Eructation cycles
  • Every 1-2 mins
  • Result in erucation
  • Rumen dorsal wall contraction then ventral sac contraction
  • displaces gas into cardia, leads to eructation assisted by anti-peristaltiv wave
  • Most gas first inspired before being released
  • Primary and secondary contractions independent
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20
Q

Describe process of regurgitation in the ruminant

A
  • Additional contraction
  • Reticular contraction floods cardia
  • Inspiratory effort, closed upper airway, expands thorax, reduce pressure in thorax and expanding oesophagus
  • lower oesophageal sphincter opens, material propelled forward by abdominal effort
  • Antiperistaltic wave in oesophagus transfers bolus to mouth
  • Liquid component reswallowed and fibre component masticated approx 50 more times before being swallowed
  • occurs between primary cycles
  • Occupies 6-12 hours per day depending on diet
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21
Q

Describe how the rumen-reticulo contractions are regulated

A
  • Integration centre in brainstem
  • Sensory cells in forestomach - info via vagal nerves
  • Stretch sensitive, mechano and chemoreceptors (stretch, pH, osmolarity, VFA concentration)
  • Motor supply via vagal nerve
  • vago-vagal reflex
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22
Q

Breifly outline the structure of the omasum

A
  • Broadly spherical, slightly flatterned sides
  • Approx 100 laminae, covered with conical papillae, increase SA
  • Relatively smaller in sheep and goats
  • Curtained appearance
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23
Q

Briefly outline the function of the omasum

A
  • Function unclear
  • Possible water absorption
  • Regular biphasic contractions, squeeze material into recesses and tehn general contraction progresses fluid forward
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24
Q

Briefly outline the structure of the abomasum

A
  • Similar to monogastric structure
  • fundus, body (corpus), pylorus
  • Larger in sheep and goats
  • A dozen large folds
  • Columnar epithelium
    Glands producing mucus, pepsinogen, HCl
  • pH ~ 3-4
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25
Q

Briefly outline the function of the abomasum

A
  • Similar to monogastric function
  • Protein digestion in ruminants (can occur in rumen-reticulum and abomasum)
  • Weak rhythmical contractions
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26
Q

Describe the appearance of the wall of the rumen

A

Covered in papillae (sheet)

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27
Q

Describe the appearance of the wall of the reticulum

A

Hexagonal shapes, papillae

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28
Q

How is the development of papillae in the rumen related to diet?

A
  • Vary in shape and size depending on diet, age and location
  • High concentration of VFAs (esp butyrate) promote growth
  • Take time to adapt to dietary changes
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29
Q

What is the oesophageal groove reflex also known as?

A

The reticular groove reflex

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30
Q

Give a basic overview of the digestion of milk in the abomasum

A
  • Milk digested in abomasum
  • Fundic glands produce rennin
  • Rennin coagulates casein milk protein) in acidic environments
  • Clot retains milk to allow complete digestion by pepsin
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31
Q

What happens to milk in the rumen?

A

Ferments, causing scour and digestive upsets

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32
Q

What is the function of the reticular groove reflex?

A

Prevents milk entering the rumen and thus reduces the risk of scour

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33
Q

Describe how the oesophageal groove reflex works

A
  • Directs milk from oesophagus into amasal canal and onwards to abomasum
  • When stimulated, groove contracts
  • Forms closed tube
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34
Q

What is the reticular groove reflex stimulated by?

A
  • Suckling milk

- Feeding routine in artificailly reared calves

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35
Q

How is the reticular groove reflex “turned off”?

A
  • After birth, forestomach starts to grow and develop
  • Promoted by presence of forage in rumen
  • Is becuase young animal starts to pick at solid food
  • Rumen flora develops within a couple of weeks of birth
  • By time animals weaned, forestomach capable of digesting adult diet
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36
Q

What is the significance of stomach tubing lambs and calves?

A

Can easily flood rumen with milk

Not catastrophic but does not acheive aim

37
Q

Describe the bacterial flora of the rumen and related chambers

A
  • more than 200 species
  • Most non spore-forming anaerobes
  • No host specificity
38
Q

Descibe the fungal flora of the rumen and related chambers

A
  • Strict anaerobes
  • Motile zoospore phase, vegetative sporangium phase
  • In vegetative found attached to food particles which penetrate pant cell walls
  • Gennus Neocallimastix
  • 12 species
  • Digest plant material by secretion of enzymes
  • Mechanical effect on structure as forms hyphae within material
  • can utilise polysaccharides (cellulose), sugars, carbohyrates but not all
  • Colones plant fragments in rumen of cattle and sheep on high fibre diets
  • Actively ferment cellulose, resulting in generation of mixture of products
39
Q

Describe the protozoal flora of the rumen and related chambers

A
  • More than 100 species
  • Most ciliates
  • 2 families - Isotrichidae (holotrichs), Ophryoscolecidae
  • Single celled eukaryotes
  • Can be predators for unicellular or filamentous algae, bacteria, microfungi
  • Control bacterial population and biomass
  • Good indicators of rumen health
  • Pick up from other animals (or parents)
  • sensitive to low pH
  • Each genus has specific effect on rumen fermentation
  • Absence does not adversely affect animal
  • Absence can be beneficial under certain dietary conditions
40
Q

What is used by the rumen microbes?

A
  • Proteins
  • Sugar, acid, lipid
  • Nitrogen
41
Q

What is produced by the rumen microbes?

A
  • Methane
  • Carbon dioxide
  • cofactors and metabolic intermediates (vit B12, aromatic growth factors, interspecies hydrogen transfer)
  • cytochrome synthesis
42
Q

What is produced by the rumen microbes?

A
  • Methane
  • Carbon dioxide
  • cofactors and metabolic intermediates (vit B12, aromatic growth factors, interspecies hydrogen transfer)
  • cytochrome synthesis
43
Q

Describe the Isotrichidae family of protozoa

A
  • Ovoid organisms
  • Covered in cilia
  • Include genera: Isotricha, Dasytricha
44
Q

Describe the Ophryoscolecidae family of protozoa

A
  • Vary in size and shape
  • Cannot utilise cellulose
  • Include genera: Entodinium, Diplodinium, Epidinium, Ophryoscolex
45
Q

What is produced by fungi in teh fermentation of cellulose?

A
  • Acetate
  • Lactate
  • Ethanol
  • Formate
  • Succinate
  • CO2
  • H2
46
Q

Describe the neocallimastix life cycle

A
  • Zoospore encysts and germinates
  • Growth by digestion of material
  • Sporangium develops
  • Release of new spores
47
Q

Describe the neocallimastix life cycle

A
  • Zoospore encysts and germinates
  • Growth by digestion of material
  • Sporangium develops
  • Release of new spores
48
Q

What are the benefits of microbial fermentation?

A
  • High quality protein from poor material
  • Vertebrates cannot synthesise essential amino acids, mixture of fermentative microbes can synthesise all
  • Synthesis of protein from non-protein nitrogen sources (urea)
  • can produce all B vitamins (only 2 synthesised in mammals)
49
Q

Explain how and why pH is maintained with relation to rumen microflora

A
  • Acid (VFA) production can lower pH
  • Buffered at 5.5-6.5 by phosphate bicarbonate buffer from saliva
  • rapid absorption of VFAs and ammonia keeps effects low
  • Prevents denaturing of microflora
50
Q

Explain how and why the redox potential is maintained with relation to rumen microflora

A
  • oxygen enters with food
  • Rapidly soaked up by bacterial population
  • Anaerobic conditions maintained, redox kept low
  • ideal conditions for microflora
51
Q

What are somethings that can cause disruption to the rumen microflora?

A
  • Acidosis (rapid change to concentrate diet, more neat sugars)
  • Cariation in diet (allow 2 weeks to cahnge microflora, diurnal changes, almost batch)
  • Starvation
  • Antibiotic therapy (may destroy rumen microflora)
  • Attachment flow of microorganisms in rumen
52
Q

Describe how rumen synchronicity can be maintained

A
  • Some constituents of feed metabolised quickly, others slowly
  • Balancing of feed will reduce fluctuations in nutrition and imbalances as microbiota adjusts
  • Well balanced feeds can increase efficiency of rumen fermentation
  • Feed will affect balance in what is produced
53
Q

List the features that permit continuous fermentation in ruminants

A
  • Anaerobic environment of rumen
  • Constant temperature and pH
  • Good mixing
  • Well masticated substrates ]
  • Huge fermentation vessel
  • Many long meals throughout the day
  • Microflora continuously moved into omasum, abomasum and SI
  • Rumination means digestion continues after grazing is done
54
Q

What direction do the rumen contractions go?

A

Cranial to caudal

55
Q

How are the rumen contractions in the camelid different to those in ruminants?

A
  • Ruminant go cranial to caudal

- Camelid go C2 for 2 mins, C1 for 8 contractions backwards and forwards, back to C2

56
Q

What are the 3 oesophageal diverticula of camelids?

A
  • C1
  • C2
  • C3
57
Q

Describe the C1 oesophageal diverticulum of camelids

A
  • Occupies large portion of left side of barrel
  • Primary bacterial breakdown of plant cellulose
  • Divided into cranail and caudal sac
  • Ingeta homogenous
  • Caudal and upper dorsal part of cranail sac drier
  • Finer matter in lower ventral part of cranial sac
  • Cud regurgitated from here
  • ure a cycling
  • Communicates with C2
58
Q

Describe the C2 oesophageal diverticulum of camelids

A
  • Sits on right abdominal wall
  • Smaller than C1
  • Liquid ingesta from C
  • Dorsal lesser vurvature, ventral greater curvature
  • Empties into C3 via short, thick-walled muscular tube
  • Control rate at which meterial moves into C3
59
Q

Describe the C3 oesophageal diverticulum of camelids

A
  • Below C2
  • Elongated
  • Lower right abdo wall
  • Last 1/5 contains gastric glands = true stomach
  • Initial 4/5 lined by mucinous glandular mucosa
  • Empties into diated ampulla delineating beginning of small intestine
60
Q

What are some of the physiological differences between ruminants fed on diet of only roughage and diet of mostly concentrate?

A
  • More regurgitation on roughage based
  • More bacteria as wider variety of materials in food (roughage)
  • Less secretion and not as much dilation of stomach (concentrate)
61
Q

What are some of the biochemical differences between ruminants fed on diet of only roughage and diet of mostly concentrate?

A

High concentrate iet can lead to acidosis

62
Q

Why do ruminants not need a dietary source of nutritionally essential amino acids?

A
  • Are produced by rumen microflora which are “ingested” by the ruminant
63
Q

What types of amino acids do ruminants consume?

A
  • Non-essential

- Can be split into rumen undegradable and rumen degradable

64
Q

What are the fates of rumen degradable and undegradable protein?

A
  • Undegradable sent straight to rumen and abomasum

- Rumen degradable digested by microflora

65
Q

Explain the role of microflora in protein digestion

A
  • Rumen degradable proteins digested by microflora
  • used to make microbial protein as population grows
  • Also requires source of energy
  • Vast quantities of rumen microflora flow into omasum and abomasum
  • Ruminant digest microflora
  • Good source of protein to ruminant
  • Microbes can also utilise ammonia to produce microbial protein
66
Q

Explain what is meant by “protein cycling” in ruminants

A
  • Ammonia used by microbes o form microbial protein
  • Excess ammonia to liver, used to make urea
  • Most urea excreted, some recycled to salivary glands
  • Swallowed in saliva
  • Used to make microbial protein
67
Q

List the products of carbohydrate digestion

A
  • Carbon dioxide
  • Methane
  • VFAs (acetate, butyrate, proprionate)
  • Pyruvate
68
Q

What is the impact of overfeeding non-protein nitrogen?

A
  • Increases blood levels of ammonia
  • Liver overwhelmed
  • Toxic levels in circulation
69
Q

What is the impact of a high roughage diet?

A
  • Produces more acetate
  • Is precursor of milk fat
  • If want high milk fat then feed low yielding cows more roughage
70
Q

What is the impact of a high concentrate diet?

A
  • Easy to break down
  • Utilises lactate pathway to produce lots of proprionate
  • Can lead to acidosis
  • Chronic and acute acidosis
71
Q

Briefly outline chronic acidosis

A
  • more common
  • High producing animals fed high concentrate diets
  • Suboptimal rumen function
  • Microflora constantly exposed to low pH
  • leads to reduced food intake, pain, indigestion, loose faeces, low milk fats
72
Q

Briefly outline acute acidosis

A
  • Usually result of “grain engorgement”
  • Break into feed store and eat as much as possible
  • Rapidly fatal
  • Water absorbed into rumen, hyppovolemic shock
  • Surgically remove carbs from rumen
73
Q

Describe carbohydrate digestion in the ruminant

A
  • Complex carbs borken down to simple sugars using extracellular enzymes of rumen microflora
  • beta-linked carbs (cellulose) digest by bacteria (mostly)
  • Attach closely to food particles
  • Simple sugars taken up rapidly by microflora and metabolised intracellularly to VFAs - anaerobic
  • Also produces pyruvate by glycolysis
74
Q

Briefly describe the production of VFAs in the rumen

A
  • Breakdown of carbs
  • Pyruvate intermediate step
  • VFAs - acetate, butyrate, proprionate
  • Excreted by baceria as waste products, used by ruminant
75
Q

Outline the steps form pyruvate to acetate

A

Pyruvate -> acetyl phosphate -> acetate

76
Q

Outline the steps from pyruvate to butyrate

A

Pyruvate -> acetyl CoA -> acetoacetyl CoA -> beta-hydroxybutyryl CoA -> crotonyl CoA -> Butyryl CoA -> butyrate

77
Q

How many pathways are there to get from pyruvate to proprionate?

A

4

78
Q

What happens to the production of proprionate if ruminants are fed a high concentrate diet?

A
  • Increases
  • Also produce lactate
  • lactate is strong acid, strong effect on rumen acidity
79
Q

How does gassy bloat occur?

A
  • Something blocks are reduces normal eructation
  • Physical obstruction
  • Cessaction of normal ruminants (ruminal acidosis, vagal iindigestion)
  • Gas unable to reach oesophagus e.g. in lateral recumbency
80
Q

How does frothy bloat occur?

A
  • Eating pasture with high quantity of soluble leaf proteins
  • Gassy foam in rumen
  • Cannot be removed by eructation
81
Q

What is absorbed from the forestomach?

A
  • VFAs
  • Ions
  • Water
82
Q

Where does the majority of absorption take place in the ruminant?

A
  • The rumen-reticulum
83
Q

What histological feature do all of the forestomachs have in common?

A
  • All have keratinised stratified squamous mucosal epithelium
  • Non-glandular
84
Q

Briefly describe the histological appearance of the omasum

A
  • Mucosa
  • Submucosa
  • Continuous muscularis mucosa
  • Serosa
85
Q

Briefly describe the histological appearance of the reticulum

A
  • Mucosa
  • Submucosa
  • Discontinuous muscularis mucosa
  • Serosa
86
Q

Briefly describe the histological appeance of the rumen

A
  • Mucosa
  • Submucosa
  • No muscularis mucoa
  • Serosa
87
Q

What features of the abomasum make an LDA possible?

A
  • Shape
  • Gas filled
  • Not tightly fixed
  • Attached to greater and lesser omentum
88
Q

Explain how an LDA may occur

A
  • After calving
  • Space in abdomina cavity once calved
  • Abomasum can move
  • Gas trapped in abomasum so lifts under rumen up on the left side most commonly

GI (31 decks)

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