1、Rumen FermentationRumen FermentationnWorlds largest commercial fermentation spacen100 billion liters or rumen volume in domestic animalsn1010 to 1012 cells/mLnRumen capacity ranges from less than 1 liter(1 quart)in a duiker to 200 liters(50 gallons)in a cowRuminantsnContinuous culture fermentersnInp
2、ut and outputnLignocellulosic substrates(forages)digestedCellulase complexHemicellulasesNitrogen capture(NPN)n8 x 1015 mouths to feedBecause of these microbial enzymes,ruminants can utilize feedstuffs that provide little to no nutritional benefit to non-ruminantsFour Steps of RuminationnRegurgitatio
3、nnReverse peristalsis carries food to mouthnRemasticationnLiquid squeezed from bolus and swallowednBolus chewednReinsalivationnAdding more salivanRedeglutitionnSwallowing bolus and liquidsRuminationnAllows animal to forage and eat food rapidly,and then store for later digestionnReduces particle size
4、nOnly small particles leave reticulorumennIncreases surface area for microbial attachment and digestion/fermentationnBreaks down impervious plant wallsnFurther stimulation of saliva flow(saliva serves to buffer rumen)Rumination TimenAverage times for a grazing animalnEating 8 hoursnRuminating 8 hour
5、snResting 8 hoursnRuminating time is quite variable(high variation)nReducing forage:concentrate decreases ruminationnReducing particle size of forage decreases time spent ruminatingMechanism of Rumination:RegurgitationnStimulus digesta in fiber mat scratching surface near cardiac sphincternContracti
6、on of the reticulum forces digesta to cardianAnimal inhales with epiglottis closed to produce a vacuumnCardia sphincter opens and esophagus dilatesnNegative pressure(vacuum)sucks digesta into esophagusnRapid reverse peristalsis moves digesta to mouthMechanism of Rumination:Remastication,Reinsalivati
7、on,and RedeglutitionnBolus is rechewednChewing is slower and more deliberate than during initial eating phasenDigesta reinsalivatednParotid glands secrete more saliva during rumination than eatingnSaliva from parotid glands secrete more NaHCO3-than other glandsnReswallowingnAfter reswallowing,the ru
8、men contracts to move swallowed bolus into the rumenRemastication and RedeglutitionReducing Particle Size of Ingested FeedsnChewing during eating(minimal)nPreparation for swallowingnRelease soluble constituentsnDamage plant tissues for microbial attachmentnChewing during remastication(extensive)nDec
9、rease particle size for passagenDamage plant tissues for microbial attachmentnMicrobial digestionnReticuloruminal contractionsRumen ContractionsnInoculate incoming feed with microbesnMix contentsnMinimize effects of stratificationnMove fermentation products(VFAs)to rumen wallnParticle sorting and pa
10、ssage of small particles to omasumnRuminationnEructation of fermentation gasesNeed for EructationnPeak gas production occurs 30 min to 2 hr post-feeding(12-27 liters/min)nAverage is 1-2 liters/minnApproximately 30%of CO2 produced in rumen is absorbed into blood and removed through the lungsnRemainde
11、r is eructatednOnly 20%of the CH4 is removed through the lungsn80%eructatedComposition of rumen gas_Gas_ _%_ CO2 65.35 CH4(variable)27.76 N2 7.00 O2 (at wall).56 H2 .18 H2S .01 Control of EructationnStimulusnGaseous distension of the reticulum and rumennEsophagus dilates&animal belchesn12-30 L per m
12、inute for cattlen3-17 times per minutenInhibitionnPresence of digesta near the cardiac sphincternAffects all three sphinctersnProtective mechanism to prevent digesta from entering lungsnEpinephrine fight or flight responsenInhibition of eructation will cause the animals to bloatnRuminal pressures wi
13、ll increase up to 100 mm HgnStable froth or foam formed in rumenFeed InVFAMicrobial ProteinVitaminsThe nutrients presented to the animal after ruminal fermentationare very different than those enteringthe rumen as feedFeed the Microbes,Let the Microbes Feed the Ruminant!Rumen Digestion and Fermentat
14、ion CO2 VFADegradable Rumen Microbial cells Feed microbes NH3 CH4 Heat Long-chain fatty acids H2SProducts in red are used by the host animalProducts listed in black are not useable by the animalRumen MicroorganismsNutritional RequirementsnCO2nEnergynEnd products from digestion of structural carbohyd
15、ratesn Fermentation of sugarsnNitrogennAmmonia(majority of nitrogen needs)nAmino acids(cellulolytic bacteria)nMineralsnCo,S,P,Na,K,Ca,Mg,Mn,Fe,Zn,Mo,SenVitaminsnNone required in mixed cultures of bacteria Symbiotic RelationshipnMicrobes provide to the ruminantnDigestion of cellulose and hemicellulos
16、enProvision of high quality proteinnProduction of VFAnProvision of B vitaminsnDetoxification of toxic compoundsDigestion of Cellulose and HemicellulosenCellulases are all of microbial originnWithout microbes,ruminants would not be able to use forage crops such as pasture,hay or silageProvision of Hi
17、gh Quality Proteinn50-80%of absorbed N is from microbesnImproved microbial efficiency will provide more microbial proteinnCan get over 3 kg of microbial protein per day in cattlenHigh biological value protein sourcenAmino acid pattern is very similar to that required by the ruminant animalMicrobes A
18、s A Feed SourcenMicrobes as a feed sourcenBacteria and protozoa washed out of the rumen to omasum and into the abomasum nAcidic environment kills microorganismsnDigested and absorbed the same as any other feed source in stomach and small intestinenProvide amino acids and some energySources of energy
19、 leaving rumen:VFA70%Microbial cells10%Digestible unfermented feed 20%No glucose available for the ruminantConcentration of VFA in rumen=50 to 125 uM/mlEnergy Provision Of B VitaminsnMeets the ruminants requirements under most conditionsnSome supplementation of specific vitamins,such as niacin,may b
20、e beneficial in early lactation dairy cowsDetoxification Of Toxic CompoundsnMany potential toxins are de-toxified by rumen microbesnExample:nMimosine in Leucaena causes problemsnPoor growth,reproduction and hair lossnHawaiian ruminants,but not those from Australia,have microbes that degrade mimosine
21、 so Leucaena could be fednTransferred rumen fluid obtaine from Hawaiian cattle to AustralianInoculated rumens of Australian cattlenFed Leucaena safely to Australian ruminants!Symbiotic RelationshipnRuminants provide to microbesnHousingnGarbage removalnNutrientsnOptimal environment for growthHousingn
22、Reliable heat(39 2C)nFluid environment(requires free water intake)n85 to 90%water nGuaranteed housing for 18 to 96 hours depending on diet and type of animalnStraw-fed water buffalo longest rumen residence time for microbesnSmall selective browsers(mouse deer or duiker)shortest residence time for mi
23、crobesGarbage RemovalnAbsorption of VFAnEnergy to ruminantnEructationnCO2 and CH4nPassage of indigestible residue and microbes to lower GI tractnRumen mixing to separate and settle small particlesNutrientsnSubstrates come from feedstuffs that animal consumesnSaliva provides urea(N source for bacteri
24、a)Optimal Environment For GrowthnReduced environment(little to no oxygen)nStrict anaerobic microbes in rumen interiornFunctional anaerobes near rumen wallnpH 6.0 to 7.0nSaliva contains bicarbonate and phosphate buffersnCows produce up to 50 gallons of saliva dailynContinuously secreted nMore added d
25、uring eating and ruminationnCow ruminates 10-12 hours/daynDecreases in particle size of forage reduce need for rumination,decrease chewing time,decrease saliva production,and rumen pH plummetsOptimal Environment(pH)nIf pH 5.7 rather than 6.5n50%less microbial synthesisnCellulolytic bacteria function
26、 best at pH 6.8 nRate of structural carbohydrate use is decreasednAmylolytic bacteria function best at pH 5.8nMore lactate and less acetate is producednFurther downward pH spiralnIn concentrate selectors(like deer),parotid salivary glands are 0.3%of body weightBacteria and pH ToleranceSpeciesTypepHR
27、uminococcus flavefaciensFibrobacter succinogenesMegasphaera elsdeniiStreptococcus bovisfiberfiberlactate userlactate producer6.1564.94.55Microbes%of mass Generation intervalNo./mLBacteria60-9020 min25-80 billionProtozoa10-408-36 h200-500 thousandFungi5-1024 hminimalSymbiotic RelationshipnMicrobes pr
28、ovide to the ruminantnDigestion of cellulose and hemicellulosenProvision of high quality proteinnProduction of VFAnProvision of B vitaminsnDetoxification of toxic compoundsnRuminants provide to microbesnHousingnGarbage removalnNutrientsnOptimal environment for growthRumen MicrobesnBacterian200 speci
29、es with many subspeciesn25 species at concentrations 107/mLn1010 to 1012 cells/mLn99.5%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 pr
30、otozoa and fungiEnvironmental 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 g
31、reatly 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 attachmentBenefits of Bacterial AttachmentBacterial PopulationsnCellulolytic bacteria(fiber digesters)nDig
32、est cellulosenRequire pH 6-7nUtilize N in form of NH3nRequire S for synthesis of sulfur-containing amino acids(cysteine and methionine)nProduce acetate,propionate,little butyrate,CO2nPredominate from roughage dietsMicrobial PopulationsnAmylolytic bacteria(starch,sugar digesters)nDigest starchnRequir
33、e pH 5-6nUtilize N as NH3 or peptidesnProduce propionate,butyrate and lactatenPredominate from grain dietsnRapid change to grain diet causes lactic acidosis(rapidly decreases pH)Microbial PopulationsnMethane-producing bacterianProduce methane(CH4)nUtilized by microbes for energynRepresent loss of en
34、ergy to animalnReleased by eructationRumen MicrobesnProtozoanLarge(20-200 microns)unicellular organismsnIngest bacteria and feed particlesnEngulf feed particles and digest carbohydrates,proteins and fatsnNumbers affected by dietEntodinium(Rumen Protozoa)Rumen MicrobesnFunginKnown only for about 20 y
35、earsnNumbers usually lownDigest recalcitrant fiberLocation of MicrobesRumen WallRumen FluidFiber MatGas PhaseDietary Factors That Reduce Microbial GrowthnRapid,dramatic ration changesnTakes 3-4 weeks for microbes to stabilizenRestricted amounts of feednExcessive unsaturated fatnBacteria do not use f
36、at for energynInhibit fiber digestion and microbial growthnDifferent types of fat have different effectsDietary Factors That Reduce Microbial GrowthnExcessive non-structural carbohydratenLowers rumen pH(rumen acidosis)nSlug feedingnFeed barley or wheat(rapidly fermented)nTo prevent acidosis,must bal
37、ance lactate users and producersDietary Factors That Maximize Microbial GrowthnMaximum dry matter intakenBalanced carbohydrate and protein fractions at the same timenBacteria need both energy and N for amino acid synthesisnGradual ration changesnFeed available at all times nMaintains stable rumen pHRumen Function Overview
