Genetic Parameters for Milk Production and Persistency

《Genetic Parameters for Milk Production and Persistency》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。

1、J.DairySci.85:1607–1616AmericanDairyScienceAssociation,2002.GeneticParametersforMilkProductionandPersistencyforDanishHolsteinsEstimatedinRandomRegressionModelsusingREMLJ.H.Jakobsen,*P.Madsen,†J.Jensen,†J.Pedersen,*L.G.Christensen,‡andD.A.Sorensen†*DanishAgricultur

2、alAdvisoryCenter,Udkaersvej15,DK-8200AarhusN,Denmark†DanishInstituteofAgriculturalSciences,DepartmentofAnimalBreedingandGenetics,P.O.Box50,DK-8830Tjele,Denmark‡RoyalVeterinaryandAgriculturalUniversity,DepartmentofAnimalScienceandAnimalHealth,Groennegaardsvej3,DK-18

3、70Frb.C,DenmarkABSTRACTINTRODUCTION(Co)variancecomponentsformilk,fat,andproteinTraditionally,aggregated305-dyieldshavebeenyieldof8075first-parityDanishHolsteins(DH)wereusedasthebreedinggoalforproductionindairycattle.estimatedinrandomregressionmodelsbyREML.ForThe305-

4、dyieldshavebeenestimatedfromindividualallanalyses,thefixedpartofthemodelwasheldcon-test-dayrecordsaccordingtorelativelysimplerulesstant,whereasfourdifferentfunctionswereappliedtogivenbySargentetal.(1968).Thatthe305-dyieldsmodeltheadditivegeneticeffectandthepermanent

5、arepredictedfromfewobservationsmaygiverisetoenvironmenteffect.Homogeneousresidualvariancebias(Andersonetal.,1989).Furthermore,shortlacta-wasassumedthroughoutlactation.Univariatemodelstionsonculledcowsorrecordsinprogressmustbewerecomparedusingaminimumof−2ln(restrict

6、edextended,whichalsomayleadtobias.Extensionproce-likelihood)asthecriterionforbestfit.HeritabilitiesasduresusedintheDanishevaluationsystemhavebeenafunctionoftimewerecalculatedfromtheestimateddescribedbyPedersen(1980)andlaterupdatedbyAa-curveparametersfromunivariatean

7、alyses.Indepen-mandetal.(1999).Biasesintheextendedrecordsmaydentofthefunctionappliedandthetraitinquestion,beduetoindividualvariationintheshapeofthelacta-heritabilitieswerelowestinthebeginningofthelacta-tioncurve(Shanksetal.,1981;PanderandHill,1993).tion.Heritabilit

8、iesforpersistencyoffatyieldwereFurthermore,accumulatedyieldsmaybeinfluencedbyslightlyhigherthanheritabilitiesforpersistencyofdifferenttemporalenvi