A review of poultry welfare in conventional production system

摘要

Theconventionalproductionsystemshavethepotentialtoinfluencepoultrywelfareinbothpositiveandnegativeways.Thebatterycageforegg-layinghensisperhapstheoldestoftheintensiveanimalfarmingsystemsstillinwidespreadusetoday.However,theconcernregardingconventionalcagesisthatbehavioralrestrictionisinherenttothesystemandhensarepreventedfromexpressinghighlymotivatedbehaviorsfortheirentirelayinglifespan.Non-cagesystemsenabletheexpressionofamorediversearrayofancestralbehaviorpatterns,withthegreatestbehavioraldiversityoccurringinfree-rangesystems.Moreover,osteoporosisandbonefractureduetogeneticimprovementforhigheggproductionhasseriousanimalwelfareimplicationsincommerciallayerflocks.Increasingthestockingdensityofbroileroperationsisawayinwhichproducerscanincreasetheirreturnoninvestment.Theydoincreasetheirrisklevelsaswell,astheconsequencesofhighstockingdensitymayleadtoincreasinghealthproblemsandreducedlivability.Dueinparttogeneticselectionforunnaturallyfastgrowth,muscleoutpacesbonedevelopmentduringtheearlylifeofpoultry,leadingtoproblemswithskeletalweakness.Asaresult,broilersoftensufferfromlegdeformitiesandlameness.Legdisorders,besidesbeingamatterofgreatconcernfromthewelfarestandpoint,alsocausepoorfeedconversion,cullingandhighmortalityofthepoultryresultingindirectfinanciallossforproducers.Themajordiseaseswithwelfareimplicationsascitesandsuddendeathsyndromeandthesehavebeenexacerbatedbyintenseselectionforfastgrowthrateandincreasedfeedefficiency.Thereisanincreasedmortalityassociatedwithfastergrowthrateswhereasslowergrowthrateshavealowermortality.Geneticprogresscreatesmanagementandnutritionalchallengesthatconfrontproducersbecausebroilersandbroilerbreederflocksarelesstoleranttomanagementanddiseaseproblemsthantheywereyearsago.Anumberofdiseaseswhicharerelatedtoundesirablechangesinmetabolismarealsoincreasinglythreateningthehealthandwelfareofpoultry.Progresscanbemadeinreducingandeliminatingpoultrywelfarebygeneticmeansandalsobyalterationofhusbandrypractices.