Digestion in the Ruminant

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AL 757 Special Topics in Rumen Microbiology
LEC 05
Digestion in Ruminant Animals
Lab. of Rumen Microbiology and Biotechnology,
GSNU, Korea.
Sung Sill Lee
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Digestion in the Ruminant
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Digestion in the Ruminant

• Largest of herbivores
• Main fxn of complex stomach of ruminant
• Utilize the largest CHO source in the world as an
  energy source
• Produce food and other products

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Anatomy
Large Intestine
Esophagus
Cecum
Rumen
Mouth
Reticulum
Abomasum
Small Intestine
Omasum
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Digestion in the Ruminant

• Mouth
• No upper teeth
• Dental pad

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Digestion in the Ruminant

• Mouth
• No upper teeth
• Dental pad
• Particle size reduction by teeth grinding against
  dental pad
• Saliva
• Moistens food
• More importantly provides buffer for rumen
• Rumen microorganisms produce
• Volatile Fatty ACIDS

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Digestion in the Ruminant

• Esophagus
• Same general fxn as in monogastric
• Complex stomach comprised of four compartments
• Rumen
• Contents 20 BW of animal
• Volume
• 5 60 gallons liquid
• 5 50 lb dry material

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Digestion in the Ruminant

• Stomach complex cont
• Reticulum
• Omassum
• Abomasum
• True glandular stomach
• Lined with mucous membrane and gastric juice
  secreted

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Digestion in the Ruminant

• Rumen/reticulum and omassum collectively term
• ??? Forestomachs ???
• Lining of these tissues
• Stratified squamous epithelium
• layered, scaly epithelium
• Not glandular
• No secretions

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Digestion in the Ruminant

• Esophageal groove (reticular groove)
• Groove which can contract and form tube to bypass
  rumen/reticulum
• Empties into omasum
• Fxn
• Allow milk to pass directly to omasum and
  abomasum
• Keep milk out of young ruminants undeveloped
  rumen

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Digestion in the Ruminant

• Rumen - Anatomy/Function
• Main fxn act as site of anaerobic bacterial
  fermentation
• Anaerobic microorganisms live and reproduce
• No oxygen anaerobic
• Undeveloped at birth sterile
• Partially developed at 4-6 weeks of age
• 1st place food goes in adult
• Some nutrients bypass anaerobic fermentation

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Digestion in the Ruminant

• Rumen wall covered with papillae
• Small finger-like projections.
• Increase surface area.
• Influence by diet and season.
• Storage of food
• Consume large amounts can digest later.
• Regurgitation, remastication, etc.

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Digestion in the Ruminant

• Microorganisms in the rumen digest
• CHO cellulose and starch
• Fermentations produces Volatile Fatty Acids

Fiber (cellulose) Corn (starch)
VFAs
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Digestion in the Ruminant

• VFAs
• Acetate/acetic acid (2 carbons)
• Propionate/propionic acid (3 carbons)
• Butyrate/butyric acid (4 carbons)

• VFAs absorbed through rumen wall
• Can supply 50-100 of required energy for ruminant

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Digestion in the Ruminant

• Main benefit of microbial fermentation
• Produce microbial protein as they live and
  reproduce

Urea Protein AA
NH3
MCO protein
C skeleton
VFAs

• Utilize urea (non-protein source)
• Utilize plant/animal protein

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Digestion in the Ruminant

• Bacteria pass through rumen with feed to lower
  G.I. Tract
• Protein (feed and microbial)
• Microbial protein contains 50 CP
• Excellent protein source
• Microorganism also synthesize
• B vitamins thus no reqt
• Vitamin K
• Microorganism also contain
• 1 2 CHO
• 3 fat essential FAs present no reqt for FA

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Digestion in the Ruminant

• Rumen provides favorable environment for
  microbial growth due to
• Buffered pH
• Temperature maintained at 101 to 103 degrees
• Primarily a liquid media
• Food supply replenished daily
• End products of digestion removed
• Anaerobic

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Digestion in the Ruminant - 2

• Anatomy continued
• Reticulum Honey Comb
• Fxn Site of microbial action absorption of
  VFAs
• Fxn Pacemaker for rumen contractions
• Contractions start in reticulum spread to rumen
• Mixes rumen contents

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Digestion in the Ruminant - 2

• Anatomy continued
• Reticulum Honey Comb
• Heavy particles move to bottom, lighter ones
  float
• Lighter particles subject to ruminationRuminatio
  n regurgitation, remastication, resalivation,
  reglutition

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Digestion in the Ruminant - 2

• Omasum many piles, lamina propia
• Fxn is unclear
• Some water and VFA absorption
• Some mechanical digestion from lamina
• Regulates particle size flowing to abomasum/S.I.
• Abomasum
• True stomach
• Secretions
• HCI denatures protein, but also kills MCO
• Mucin, pepsin, etc

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Digestion in the Ruminant - 2

• Small intestine, large intestine
• Very similar to that for non-ruminant
• Post Gastric Fermentation
• Approximately 5-15 of cellulytic digestion can
  occur in colon and cecum
• MCO here as well but lost in feces, lose MCO
  protein
• VAs produced and can be absorbed through L.I.
• Primary function is still water absorption

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Rumination Process
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Rumination Process

• Define set of steps that reduce particle size
  of digesta for passage to lower tract
• Regurgitation
• Bolus is moved by reverse contraction of
  esophagus from rumen to mouth
• Remastication
• Reduce particle size
• Resalivation
• Buffer
• Nitrogen recycling
• Reglutition

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Eructation

• Process of removing gas from the rumen
• 50 200 liters/day
• Gases produced H2 hydrogen CO2 carbon
  dioxide CH4 methane H2S hydrogen sulfide

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Eructation

• Rumen contraction forces gas to the back and then
  forward
• Gas forced up esophagus to the trachea

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Eructation

• Problem Bloat
• Primarily caused by inability to eructate
• Froth
• Foam
• Secondarily caused by something anatomically
  wrong
• Commonly seen distention of left side

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Bloat
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Eructation

• Problem Bloat
• Primarily caused by inability to eructate
• Froth
• Foam
• Secondarily caused by something anatomically
  wrong
• Commonly seen distention of left side
• Legumes (soluble protein) primary cause
• Barn door left open wheat pasture, lush grass
• Treatment/prevention
• Trochar
• Ionphores

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Fermentation Process
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Fermentation Process

• Rumen MOs and ruminant animal live in SYMBIOSIS
• The animal benefits because MOs digest feeds
• The MOs benefit from having a nice Condo
• Feeding ruminant complicated
• Feeding MOs
• Feeding animal

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Fermentation Process

• Rumen environment maintained by animal
• Warmth, 101-105 degrees F
• Moisture
• Daily food supply animal eats
• pH controlled salivation
• Dark no UV light
• Mixing
• Oxygen free
• End products removed absorbed or passed
• Ruminates and masticates decrease particle size

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Fermentation Process

• Microbial Species
• Bacteria
• Vast Number of types may be found in rumen
• 15-50 billion/ml
• Digestion various nutrients
• Ex. Cellulose, starch, protein digesters
• Protozoa
• 35 species of ciliated protozoa
• 20,000 500,000/ml
• Most protozoa prey on bacteria

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Fermentation Process

• Yeast ( fungi)
• Small amount
• Aid in cellulose breakdown
• Total of MOs in rumen assuming 50 liter
  capacity
• 2.5 X 1015 microorganisms
• 2,500,000,000,000,000

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Fermentation Process

• General Fermentation Reactions

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Fermentation Process

• End products of fermentation
• VFA
• Types of VFA

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Fermentation Process

• End products of fermentation
• VFA
• Microbial protein
• B vitamins
• MOs
• Vitamin K
• Essential Lipids

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Fermentation Process

• VFAs are passively diffused through rumen wall
• Importance of VFA
• VFA contribute 50-100 of required energy

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Fermentation Process

• VFA concentrations
• Concentrate diets (rumen fluid)
• 100 120 mmol per ml VFA
• 5.5 6.0 pH
• Forage diets
• 60 - 80 mmol per ml VFA
• 6.5 7.0 pH

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Fermentation Process

• Gas production
• 65 CO2
• 25 CH4
• 7 N2
• Some O2,H2, H2S

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Fermentation Process

• NH3
• By product of deamination of AA
• Incorporated into MO protein
• Absorbed through rumen wall
• Nitrogen recycling
• Urination
• Heat
• Major product of fermentation
• Useful in winter
• Detriment in summer

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Fermentation Process

• CHO fermentation
• Starch feedlot, grain diet
• Fiber grass, silage diets
• Alteration of CHO fermentation
• Ionophores feed additives
• Shift MO to propionic producing species
• Rumensin Lasalocid
• Originally approved as coccidiostat for poultry
• Animals response is improved FE or ADG

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Fermentation Process

• VFA production differs with diet
• Forage diet
• 65 Acetate
• 20 Propionate
• 12 Butyrate
• Grain diet
• 45 Acetate
• 35 Propionate
• 15 Butyrate

Acetate Propionate (ratio)
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Fermentation Process

• Lipid fermentation
• MOs saturate otherwise unsaturated fatty acids
• Reason ruminants deposit saturated fat
• Excessive fat levels decrease fiber digestion
• gt 10 diet
• Coats the feed
• N. Protein Fermentation

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Feed Crude Protein

RUMEN
S. Intestine
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Protein Fermentation

• Fate of dietary protein
• Type of protein
• Mostly escape or mostly soluble
• Rate of fermentation
• How fast can the bugs break it down?
• Rate of passage
• How fast does it leave the rumen?

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Rumen Acidosis
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Rumen Acidosis

• Lactic Acidosis
• Can occur in feedlot cattle, sheep, dairy cow
• Generally due to high levels of concentrate
  (corn) in diet
• Why does it occur??
• Rapid increase in grain in diet
• Rapid change from forage to concentrate
• Barn door left open
• Grazing residue crop
• Improper ration balancing /or management

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Rumen Acidosis

• Large changes in lactic acid producing bacteria
• Due to increase in readily available CHO source
• pH decrease to 4.5 to 5.0
• pH decrease kills off good MOs
• Lower pH goes sicker the animal gets
• Symptoms
• Decrease intake
• Abdominal pain
• Dehydration sunken eyes, staggers, coma death
• Laminitis

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Rumen Acidosis

• Physiology
• Acid absorbed lowers pH of blood
• Keratinization of rumen wall
• Osmotic changes influx of water into rumen
  Dehydration damage to rumen wall
• Management
• Have adequate roughage in diet
• Adapt animals to new diets slowly
• Feed buffer
• Liver abscesses
• Antibiotics Tylan, Chlortetracycline