rumen fermentation
DESCRIPTION
generalidades de la fermentacion ruminalTRANSCRIPT
Rumen Fermentation
Rumen Fermentation World’s largest
commercial fermentation space 100 billion liters or
rumen volume in domestic animals
1010 to 1012 cells/mL
200 liters (50 gallons) in one cow
Ruminants Continuous culture fermenters
Input and output Lignocellulosic substrates digested
Cellulase complex Hemicellulases Lysozyme Nitrogen capture (NPN)
8 x 1015 mouths to feedBecause of these microbial enzymes, ruminants can utilize feedstuffs that provide little to no nutritional benefit to nonruminants
4 Steps of Rumination Regurgitation
reverse peristalsis carries food to mouth
Remastication liquid squeezed from bolus and
swallowed bolus chewed
Reinsalivation adding more saliva
Redeglution swallowing bolus and liquid
Rumination Allows animal to forage and eat food
rapidly, and then store for later digestion Reduces particle size
only small particles leave reticulorumen Increases surface area for microbial
attachment and digestion/fermentation Breaks down impervious plant walls Further stimulation of saliva flow (buffer
rumen)
Rumination Time Average times for a grazing animal
Eating – 8 hours Ruminating – 8 hours Resting – 8 hours
Ruminating time is quite variable Reducing forage:concentrate decreases
rumination Reducing particle size of forage decreases
time spent ruminating
Mechanism of Rumination: Regurgitation
Stimulus – digesta in fiber mat scratching surface near cardiac sphincter
Contraction of the reticulum forces digesta to cardia
Animal inhales with epiglottis closed to produce a vacuum
Cardia sphincter opens and esophagus dilates
Negative pressure (vacuum) sucks digesta into esophagus
Rapid reverse peristalsis moves digesta to mouth
Mechanism of Rumination: Remastication, Reinsalivation, and Redeglutition
Bolus is rechewed Chewing is slower and more deliberate than
during initial eating phase Digesta reinsalivated
Parotid glands secrete more saliva during rumination than eating
Saliva from parotid glands secrete more NaHCO3-
than other glands Reswallowing
After reswallowing, the rumen contracts to move swallowed bolus into the rumen
Reducing Particle Size of Ingested Feeds
Chewing during eating (minimal) Preparation for swallowing Release soluble constituents Damage plant tissues for microbial attachment
Chewing during rumination (extensive) Decrease particle size for passage Damage plant tissues for microbial attachment
Microbial digestion Reticuloruminal contractions
Rumen Contractions Inoculate incoming feed with microbes Mix contents
Minimize effects of stratification Move fermentation products (VFA’s) to
rumen wall Particle sorting and passage of small
particles to omasum Rumination Eructation of fermentation gases
Rumen Contractions
Feeding increases frequency and amplitude of contractions
Feeding a finely ground forage reduces number and intensity of contractions Requires 2-6 weeks to adapt
Metabolic problems Hardware disease, hypocalcemia, or
hyperglycemia will inhibit ruminal contractions
Need for Eructation Peak gas production occurs
30 min to 2 hr post-feeding (12-27 liters/min)
Average is 1-2 liters/min Approximately 30% of CO2
produced in rumen is absorbed into blood and removed through the lungs
Only 20% of the CH4 is removed through the lungs
Composition of rumen gas
__Gas__ _%__ CO2 65.35 CH4 (variable) 27.76 N2 7.00 O2 (at wall) .56 H2 .18 H2S .01
Control of Eructation Stimulus
Gaseous distension of the reticulum and rumen Esophagus dilates & animal belches
12-30 L per minute for cattle 3-17 times per minute
Inhibition Presence of digesta near the cardiac sphincter
Affects all three sphincters Protective mechanism to prevent digesta from entering lungs
Epinephrine Histamine
Inhibition of eructation will cause the animals to bloat
Ruminal pressures will increase to 45 to 100 mm Hg Stable froth or foam formed in rumen
Why Worry about Rumen Microbes? Microbes make ruminants less
efficient!!
Aerobic fermentation:
Anaerobic fermentation:
Glucose + O2 ATP + CO2 + H2O
Glucose acetic acid + propionic acid + butyric acid + CO2 + H2O + CH4 + Heat
Feed InVFAMicrobial ProteinVitamins
The nutrients presented to the animal after ruminal fermentationare very different than those enteringthe rumen as feed
Feed the Microbes, Let the Microbes Feed the Ruminant!
Rumen Digestion and Fermentation
CO2 VFA
Degradable Rumen Microbial cells Feed microbes NH3
CH4 Heat Long-chain fatty acids H2S
Rumen MicroorganismsNutritional Requirements
CO2 Energy
End products from digestion of structural carbohydrates fermentation of sugars
Nitrogen Ammonia (majority of nitrogen needs) Amino acids (cellulolytic bacteria)
Minerals Co, S, P, Na, K, Ca, Mg, Mn, Fe, Zn, Mo, Se
Vitamins None required in mixed cultures
Symbiotic Relationship Microbes provide to the ruminant
Digestion of cellulose and hemicellulose
Provision of high quality protein Production of VFA Provision of B vitamins Detoxification of toxic compounds
Symbiotic Relationship Microbes provide to the ruminant
Digestion of cellulose and hemicellulose
Cellulases are all of microbial origin Without microbes, ruminants would not
be able to use forage crops such as pasture, hay or silage
Symbiotic Relationship Microbes provide to the ruminant
Provision of high quality protein 50-80% of absorbed N is from microbes
Improved microbial efficiency will provide more microbial protein
Can get over 3 kg of microbial protein per day High biological value protein source
Amino acid pattern is very similar to that required by the ruminant animal
Symbiotic Relationship Microbes provide to the ruminant
Microbes as a feed source Bacteria and protozoa washed out of the
rumen to omasum and into the abomasum
Acidic environment kills microorganisms Digested and absorbed the same as any other
feed source in stomach and small intestine Provide amino acids and some energy
Microbes provide to the ruminant Energy!!!VFA 70%
Microbial cells 10%
Digestible unfermented feed 20%
No glucose available for the ruminant
Concentration of VFA in rumen = 50 to 125 uM/ml
Symbiotic Relationship
Symbiotic Relationship Microbes provide to the ruminant
Provision of B vitamins Meets the ruminant’s requirements under
most conditions Some supplementation, such as niacin, may
be beneficial in early lactation dairy cows
Symbiotic Relationship Microbes provide to the ruminant
Detoxification of toxic compounds Example:
Mimosine in Leucaena causes problems poor growth, reproduction and hair loss
Hawaiian ruminants, but not those from Australia, have microbes that degrade mimosine so Leucaena could be fed
Transferred rumen fluid to Australia Inoculated rumen Fed Leucaena safely to Australian ruminants!
Symbiotic Relationship Ruminants provide to microbes
Housing Garbage removal Nutrients Optimal environment for growth
Symbiotic Relationship Ruminants provide to microbes
Housing Reliable heat (39 ± 2°C) Fluid environment (free water intake)
85 to 90% water Guaranteed for 18 to 96 hours depending
on diet and type of animal Straw-fed water buffalo – longest rumen
residence time for microbes Small selective browsers (mouse deer or
duiker) – shortest residence time for microbes
Symbiotic Relationship Ruminants provide to microbes
Garbage removal Absorption of VFA
Energy to ruminant Eructation
CO2 and CH4
Passage of indigestible residue and microbes to lower GI tract
Rumen mixing to separate and settle small particles
Symbiotic Relationship Ruminants provide to microbes
Nutrients Substrates come from feedstuffs that
animal consumes Saliva provides urea (N source for
bacteria)
Symbiotic Relationship Ruminants provide to microbes
Optimal environment for growth Reduced environment (little to no oxygen)
Strict anaerobic microbes in rumen interior Functional anaerobes near rumen wall
pH 6.0 to 7.0 Saliva contains bicarbonate and phosphate buffers
Cows produce up to 50 gallons of saliva daily Continuously secreted More added during eating and rumination Cow ruminates 10-12 hours/day Decreases in particle size of forage reduce
need for rumination, decrease chewing time, decrease saliva production, and rumen pH plummets
Symbiotic Relationship Ruminants provide to microbes
Optimal environment (pH) If pH 5.7 rather than 6.5
50% less microbial synthesis Cellulolytic bacteria function best at pH ~6.8
Rate of structural carbohydrate use is decreased
Amylolytic bacteria function best at pH ~5.8 More lactate and less acetate is produced
Further downward pH spiral In concentrate selectors (like deer), parotid
salivary glands are 0.3% of body weight
Bacteria and pH Tolerance
Species Type pHRuminococcus flavefaciensFibrobacter succinogenesMegasphaera elsdeniiStreptococcus bovis
fiberfiber
lactate userlactate
producer
6.156
4.94.55
Microbes% of mass
Generation interval
No./mL
Bacteria 60-90 20 min 25-80 billion
Protozoa 10-40 8-36 h 200-500 thousand
Fungi 5-10 24 h minimal
Rumen Microbes Bacteria
>200 species with many subspecies 25 species at concentrations >107/mL
1010 to 1012 cells/mL 99.5% obligate anaerobes
Groups of bacteria in the rumen Free-living in the liquid phase Loosely associated with feed particles Firmly adhered to feed particles Associated with rumen epithelium Attached to surface of protozoa and fungi
Environmental Niches for Bacteria
Allows bacteria to colonize the digestible surface of feed particles
Brings enzymes (from microbes) and substrate (from feedstuff) together Protects microbial enzymes from proteases in the rumen
If attachment prevented or reduced, digestion of cellulose greatly reduced
Retention time of microbes in the rumen is increased to prolong digestion Reduces predatory activity of protozoa Over-feeding fat to ruminants can coat forages, reducing bacterial attachment
Benefits of Bacterial Attachment
Rumen Microbes Protozoa
Large (20-200 microns) unicellular organisms
Ingest bacteria and feed particles Engulf feed particles and digest
carbohydrates, proteins and fats Numbers affected by diet
Entodinium (Rumen Protozoa)
Rumen Microbes Fungi
Known only for about 20 years Numbers usually low Digest recalcitrant fiber
Bacterial Populations Cellulolytic bacteria (fiber digesters)
digest cellulose require pH 6-7 utilize N in form of NH3 require S for synthesis of sulfur-containing
amino acids (cysteine and methionine) produce acetate, propionate, little butyrate,
CO2 predominate from roughage diets
Microbial Populations Amylolytic bacteria (starch, sugar
digesters) digest starch require pH 5-6 utilize N as NH3 or peptides produce propionate, butyrate and lactate predominate from grain diets rapid change to grain diet causes lactic
acidosis (rapidly decreases pH)
Microbial Populations Methane-producing bacteria
produce methane (CH4) utilized by microbes for energy represent loss of energy to animal released by eructation
Location of Microbes
Rumen Wall
Rumen Fluid
Fiber Mat
Gas Phase
Dietary Factors That Reduce Microbial Growth Rapid, dramatic ration changes
Takes 3-4 weeks for microbes to stabilize Restricted amounts of feed Excessive unsaturated fat
Bacteria do not use fat for energy Inhibit fiber digestion and microbial growth Different types of fat have different effects
Dietary Factors That Reduce Microbial Growth Excessive non-structural
carbohydrate Lowers rumen pH (rumen acidosis)
Slug feeding Feed barley or wheat (rapidly fermented) To prevent acidosis, must balance lactate
users and producers
Dietary Factors That Maximize Microbial Growth Maximum dry matter intake Balanced carbohydrate and protein
fractions at the same time Bacteria need both energy and N for
amino acid synthesis Gradual ration changes Feed available at all times
Maintains stable rumen pH
Rumen Function Overview