Calculation of the economic values for some udder health traits to estimate the profitability of the selection indices for dairy cows in Egypt

摘要

ThreedifferentgroupsofeconomicvalueswerecalculatedforsomeudderhealthtraitstoestimatetheirprofitabilityandcompareseveralselectionindicesinaherdofFriesiancowsinEgypt.DatawereanalyzedusingMTDFREMLprogramwithamodelincludingmonthandyearofcalvingasfixedeffectsandanimalanderrorasrandomeffects.Covariancecomponentsfor305daymilkyield(MY),somaticcellcounts(SCC),clinicalmastitis(CM)andudderhealthstatus(UDHS)alongwiththeirgroupsofrelativeeconomicvalueswereusedforconstructingtheselectionindices.Thegroupsofrelativeeconomicvalueswere:(1)actualrelativeeconomicvalues,(2)actualeconomicvaluesofthegeneticstandarddeviationand(3)therelativeweightasonephenotypicstandarddeviationofthetrait.nbsp;Heritabilityestimateswere0.35,0.24,0.18and0.16forMY,SCC,CMandUDHS,respectively.Geneticcorrelationsbetweenmilkyieldandudderhealthtraitswerenegative,rangingfrom-0.75to-0.39,andbetweenudderhealthtraitswerepositiverangingfrom0.84to0.94.Correspondingphenotypiccorrelationsbetweenudderhealthtraitswerebetween0.73and0.88,butwerenegativerangingfrom-0.66to-0.46betweenmilkyieldandudderhealthtraits.nbsp;Twelveselectionindiceswereconstructedusingdifferentgroupsofthecalculatedeconomicvalues.SelectionforMY,SCC,CMandUDHSimprovedtheefficiencyofresponseoftheaggregategenotypeby8to9%overselectionformilkyieldalone.ThiswasduetoincorporatingeitheroneormoreoftheudderhealthtraitstoMYintheindices.Theselectionindicesconstructedbyeachofthethreegroupsoftheeconomicvalueswererecommendedforuseiftheselectionistobepracticedattheendofthefirstlactation.nbsp;Rankcorrelationcoefficientsamongselectionindicesof1806Friesiancowsconstructedbyusingthethreedifferentgroupsofrelativeeconomicvaluesrangedfrom0.95to1.00.Therefore,itwasrecommendedtousethethirdgroupofrelativeeconomicvaluesbecauseofitssimplicityandeaseofcalculation.ThepresentresultssuggestthattheselectionforlowerSCCandUDHSwouldhelptoreduceoreliminatetheundesirablecorrelatedresponsesofclinicalmastitisassociatedwithselectionforincreasingmilkyield.Additionally,theeconomicimpactofSCC,CMandUDHSareofsufficientmagnitudetowarranttheirinclusioninaselectioncriterionforimprovingtherevenuesrearinglactatingcows.