Non-genetic factors affecting somatic cell count, milk urea content, test-day milk yield and milk protein percent in dairy cattle of the Czech Republic using individual test-day records

摘要

Thisstudyhadtwoaims.Firstly,todeterminetheassociationsofmonthofrecording(MOR)anddaysinmilk(DIM)withsomaticcellcount(SCC),milkureaconcentration(MU)andmilkproductiontraits(i.e.test-daymilkyield,TDM;milkproteinpercentage,PPandmilkproteinyield,PY).Secondly,toevaluatetheassociationsamongSCC,MUandmilkproductiontraitsbyanalyzingindividualmonthlytest-dayrecordsfordairycowsraisedintheCzechpartoftheCzechRepublic.Atotalnumberof33,881individualtest-daymilkrecordsinvolving15,565dairycowsfora12-monthperiodbetweenJanuaryandDecember2001enrolledinDatabaseComputerCenterbelongingtoCzechMoravianBreeders′Corporation,Inc.,Hiradistko,theCzechRepublicwasused.nbsp;TheMORandDIMhadhighlysignificant(P0.001)effectsonthestudiedtraits.TheSCCreachedthemaximumlevelinSeptember(504,000)associatedtothelowestTDM(19.9kg)andthelowestSCCinDecember(320,000)andFebruary(335,000cell/ml).LeastsquaresmeansofTDM,categorizedby30-dincrementsofDIM,paralleledreversiblechangesinPPandfollowedacurvilinearshape.SCCreachedtothepeakinthe2ndand3rdmonthsoflactationthendecreasedgraduallytotheendoflactation.MUwaslower(30.5mg/dl)duringthefirst30DIMcomparedwithallotherDIMcategories.nbsp;ThestatisticalanalysisofTDM,PYandSCCbyMUshowedthatasMUincreased,TDM,PYincreasedandSCCdecreased.nbsp;MU,SCC,PPandPYweresignificantlydifferentamongTDMcategorized.nbsp;EachofPPandSCCmeasuresinverselyassociatedwithTDM,meanwhileMUparalleledchangewithTDM.nbsp;SomaticcellcountmeasuresshowedaparalleledchangewithPP.nbsp;nbsp;Theeffectsofenvironmentalvariablesandassociationsamongtraitsmustbetakenintoconsiderationwhencowsareevaluated.