The role of probiotics in the poultry industry

Int.J.Mol.Sci.2009,10,3531-3546;doi:10.3390/ijms10083531InternationalJournalofMolecularSciencesISSN1422-0067:[e-mail]2DepartmentofMicrobiologyandHygiene,FacultyofVeterinaryScience,BangladeshAgriculturalUniversity,Mymensingh-2202,BangladeshReceived:3June2009;inrevisedform:9August2009/Accepted:11August2009/Published:12August2009Abstract:Theincreaseofproductivityinthepoultryindustryhasbeenaccompaniedbyvariousimpacts,includingemergenceofalargevarietyofpathogensandbacterialresistance.Theseimpactsareinpartduetotheindiscriminateuseofchemotherapeuticagentsasaresultofmanagementpracticesinrearingcycles.Thisreviewprovidesasummaryoftheuseofprobioticsforpreventionofbacterialdiseasesinpoultry,aswellasdemonstratingthepotentialroleofprobioticsinthegrowthperformanceandimmuneresponseofpoultry,safetyandwholesomenessofdressedpoultrymeatevidencingconsumer’sprotection,withacriticalevaluationofresultsobtainedtodate.Keywords:probiotics;bacteria;diseasecontrol;meatquality;poultry1.IntroductionThepoultryindustryhasbecomeanimportanteconomicactivityinmanycountries.Inlarge-scalerearingfacilities,wherepoultryareexposedtostressfulconditions,problemsrelatedtodiseasesanddeteriorationofenvironmentalconditionsoftenoccurandresultinseriouseconomiclosses.Preventionandcontrolofdiseaseshaveledduringrecentdecadestoasubstantialincreaseintheuseofveterinarymedicines.However,theutilityofantimicrobialagentsasapreventivemeasurehasbeenquestioned,givenextensivedocumentationoftheevolutionofantimicrobialresistanceamongpathogenicbacteria.So,thepossibilityofantibioticsceasingtobeusedasgrowthstimulantsforpoultryandtheconcernabouttheside-effectsoftheiruseastherapeuticagentshasproducedaclimateinwhichbothconsumerandmanufacturerarelookingforalternatives.Probioticsarebeingconsideredtofillthisgapandalreadysomefarmersareusingtheminpreferencetoantibiotics[1-3].OPENACCESSInt.J.Mol.Sci.2009,103532Addingtheso-calledbeneficialbacteriatothedigestivetractofpoultryisnotanewconcept,however,acompleteunderstandingofwhere,whenandhowtousethemstillhasescapedusinitsentirety.AstrikinglycrucialeventinthedevelopmentofprobioticswasthefindingthatnewlyhatchedchickenscouldbeprotectedagainstcolonizationbySalmonellaenteritidisbydosingasuspensionofgutcontentsderivedfromhealthyadultchickens[4].Thisconceptiscalledcompetitiveexclusion.Theimpactofbiotechnologyinpoultrynutritionisofsignificantimportance.Biotechnologyplaysavitalroleinthepoultryfeedindustry.Nutritionistsarecontinuallyputtingtheireffortsintoproducingbetterandmoreeconomicalfeed.Goodfeedalonewillnotservethepurposebutitsbetterutilizationisalsoessential.Dietarychangesaswellaslackofahealthydietcaninfluencethebalanceofthemicroflorainthegutthuspredisposingtodigestionupsets.Awell-balancedrationsufficientinenergyandnutrientsisalsoofgreatimportanceinmaintainingahealthygut.Agreatdealofattentionhasrecentlybeenreceivedfromnutritionistsandveterinaryexpertsforproperutilizationofnutrientsandtheuseofprobioticsforgrowthpromotionofpoultry.Inbroilernutrition,probioticspeciesbelongingtoLactobacillus,Streptococcus,Bacillus,Bifidobacterium,Enterococcus,Aspergillus,Candida,andSaccharomyceshaveabeneficialeffectonbroilerperformance[5-25],modulationofintestinalmicrofloraandpathogeninhibition[7,20,26-31],intestinalhistologicalchanges[29,32,33],immunomodulation[8,10,15,19,22,34-39],certainhaemato-biochemicalparameters[7,11-12,25,39],improvingsensorycharacteristicsofdressedbroilermeat[40,41]andpromotingmicrobiologicalmeatqualityofbroilers[42].Theobjectivesofthisreviewaretodescribetheprinciples,mechanismsofactionandcriteriaforselectionofprobiotics,andtosummarizetheirapplicationsinthepoultryindustry.2.WhatIsaProbiotic?Overtheyearsthewordprobiotichasbeenusedinseveraldifferentways.Itwasoriginallyusedtodescribesubstancesproducedbyoneprotozoanwhichstimulatedbyanother[43],butitwaslaterusedtodescribeanimalfeedsupplementswhichhadabeneficialeffectonthehostanimalbyaffectingitsgutflora[44].Crawford[45]definedprobioticsas“acultureofspecificlivingmicro-organisms(primarilyLactobacillusspp.)whichimplantsintheanimaltoensuretheeffectiveestablishmentofintestinalpopulationsofbothbeneficialandpathogenicorganisms”.Fuller[46]latergaveauniquedefinitionofprobioticsas“alivemicrobialfeedsupplementwhichbeneficiallyaffectsthehostanimalbyimprovingitsintestinalmicrobialbalance”.TheUSNationalFoodIngredientAssociationpresented,probiotic(directfedmicrobial)asasourceoflivenaturallyoccurringmicroorganismsandthisincludesbacteria,fungiandyeast[47].AccordingtothecurrentlyadopteddefinitionbyFAO/WHO,probioticsare:livemicroorganismswhichwhenadministeredinadequateamountsconferahealthbenefitonthehost[48].Moreprecisely,probioticsarelivemicroorganismsofnonpathogenicandnontoxicinnature,whichwhenadministeredthroughthedigestiveroute,arefavorabletothehost’shealth[49].Itisbelievedbymostinvestigatorsthatthereisanunsteadybalanceo