4 rumen fermentation


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4 rumen fermentation

  1. 1. RumenFermentation
  2. 2. Rumen Fermentation  World’s largest commercial fermentation space  100 billion liters or rumen volume in domestic animals  1010 to 1012 cells/mL  Rumen capacity ranges from less than 1 liter (1 quart) in a duiker to 200 liters (50 gallons) in a cow
  3. 3. Ruminants  Continuous culture fermenters  Input and output  Lignocellulosic substrates (forages) digested  Cellulase complex  Hemicellulases  Nitrogen capture (NPN)  8 x 1015 mouths to feedBecause of these microbial enzymes, ruminants can utilize feedstuffsthat provide little to no nutritional benefit to non-ruminants
  4. 4. Four Steps of Rumination Regurgitation  Reverse peristalsis carries food to mouth Remastication  Liquid squeezed from bolus and swallowed  Bolus chewed Reinsalivation  Adding more saliva Redeglutition  Swallowing bolus and liquids
  5. 5. 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 (saliva serves to buffer rumen)
  6. 6. Rumination Time Average times for a grazing animal  Eating – 8 hours  Ruminating – 8 hours  Resting – 8 hours Ruminating time is quite variable (high variation)  Reducing forage:concentrate decreases rumination  Reducing particle size of forage decreases time spent ruminating
  7. 7. 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
  8. 8. 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
  9. 9. Remasticationand Redeglutition
  10. 10. Reducing Particle Size of Ingested Feeds Chewing during eating (minimal)  Preparation for swallowing  Release soluble constituents  Damage plant tissues for microbial attachment Chewing during remastication (extensive)  Decrease particle size for passage  Damage plant tissues for microbial attachment Microbial digestion Reticuloruminal contractions
  11. 11. 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
  12. 12. Need for Eructation Peak gas production Composition of rumen occurs 30 min to 2 hr post- gas feeding (12-27 liters/min)  Average is 1-2 liters/min Approximately 30% of CO2 __Gas__ _%__ produced in rumen is CO2 65.35 absorbed into blood and CH4 (variable) 27.76 removed through the lungs N2 7.00  Remainder is eructated O2 (at wall) .56 Only 20% of the CH4 is removed through the lungs H2 .18  80% eructated H2S .01
  13. 13. 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 – fight or flight response  Inhibition of eructation will cause the animals to bloat  Ruminal pressures will increase up to 100 mm Hg  Stable froth or foam formed in rumen
  14. 14. Feed the Microbes, Let the Microbes Feed the Ruminant! Feed In VFA Microbial Protein Vitamins The nutrients presented to the animal after ruminal fermentation are very different than those entering the rumen as feed
  15. 15. Rumen Digestion and Fermentation CO2 VFA Degradable Rumen Microbial cells Feed microbes NH3 CH4 Heat Long-chain fatty acids H2SProducts in red are used by the host animalProducts listed in black and green are not useable by the animalProducts listed in green are the primary energy losses from the rumen
  16. 16. Location of Microbes Gas PhaseRumen Fiber MatWall Rumen Fluid
  17. 17. Rumen Microorganisms Nutritional 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 of bacteria
  18. 18. 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
  19. 19. Digestion of Cellulose andHemicellulose Cellulases are all of microbial origin  Without microbes, ruminants would not be able to use forage crops such as pasture, hay or silage
  20. 20. 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 in cattle High biological value protein source  Amino acid pattern is very similar to that required by the ruminant animal
  21. 21. Microbes As A Feed Source 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
  22. 22. Energy Sources of energy leaving rumen: 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
  23. 23. Provision Of B Vitamins Meets the ruminant’s requirements under most conditions  Some supplementation of specific vitamins, such as niacin, may be beneficial in early lactation dairy cows
  24. 24. Detoxification Of Toxic Compounds  Many potential toxins are de-toxified by rumen microbes  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 obtaine from Hawaiian cattle to Australia  Inoculated rumens of Australian cattle  Fed Leucaena safely to Australian ruminants!
  25. 25. Symbiotic Relationship Ruminants provide to microbes  Housing  Garbage removal  Nutrients  Optimal environment for growth
  26. 26. Housing Reliable heat (39 ± 2°C) Fluid environment (requires free water intake)  85 to 90% water Guaranteed housing 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
  27. 27. 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
  28. 28. Nutrients Substrates come from feedstuffs that animal consumes Saliva provides urea (N source for bacteria)
  29. 29. 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
  30. 30. 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
  31. 31. 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 Ruminants provide to microbes  Housing  Garbage removal  Nutrients  Optimal environment for growth
  32. 32. Microbes % of mass Generation No./mL intervalBacteria 60-90 20 min 25-80 billionProtozoa 10-40 8-36 h 200-500 thousandFungi 5-10 24 h minimal
  33. 33. Rumen Microbes Bacteria  >200 species with many subspecies  25 species at concentrations >107/mL  1010 to 1012 cells/mL  99.5% obligate anaerobes
  34. 34. Environmental Niches for Bacteria 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 Bacteria attached to rice straw in water buffalo rumen
  35. 35. Benefits of Bacterial Attachment Allows bacteria to colonize the digestible surface offeed particles  Brings enzymes (from microbes) and substrate (from feedstuff) together  Protects microbial enzymes from proteases in the rumen If attachment prevented or reduced, digestion ofcellulose 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
  36. 36. Microbial Populations Cellulolytic bacteria (fiber digesters)  Digest cellulose and hemicellulose  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 in rumens of cows fed roughage diets
  37. 37. Microbial Populations Amylolytic bacteria  Digest starches and sugars  Require pH 5-6  Utilize N as NH3 or peptides  Produce propionate, butyrate and lactate  Predominate in rumens of cows fed grain diets  Rapid change to grain diet causes lactic acidosis (rapidly decreases pH)
  38. 38. Microbial Populations Methane-producing bacteria  Produce methane (CH4)  Utilized by microbes for energy  Represent loss of energy to animal  Released by eructation
  39. 39. 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
  40. 40. Entodinium (Rumen Protozoa)
  41. 41. Rumen Microbes Fungi  Existence known for about 25 years  Numbers usually low  Digest recalcitrant fiber Protozoal organisms attached to red clover in rumen of steer 24 hours after feeding
  42. 42. Dietary Factors That ReduceMicrobial 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
  43. 43. Dietary Factors That ReduceMicrobial 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
  44. 44. Dietary Factors That MaximizeMicrobial 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
  45. 45. Rumen Function Overview