Correlations between first and successive records on four traits as a basis for culling dual purpose cattle

摘要

Inordertodeterminewhetherfirstrecordscouldbeusedasabasisforculling,recordsonmilkyield,daysinmilk,daysopenand4-monthcalfweightfrom882cowsin12dualpurposeherdsweretoestimatethecorrelationbetweenfirstandsuccessiverecordsuptothefourth.Allherdswerekeptongrazingwithvariableproportionsofcultivatedpasturesandsupplementaryfeeding.Tenoftheherdsweremilkedbyhandwithcalfsuckling.Twodatasetswereused:thefirstconsistedofunadjusted(UA)performancedatatosimulatethesimplestselectionmethodavailabletofarmers.nbsp;Thesecondanalysiswasbasedonthedeviationsofeachcow'srecords(A)fromcontemporarymeansbasedonaminimumoftenrecords,withherd,calvingyear,seasonandnumberbeingtakenintoaccount.Thecorrelationsbetweenfirstandsuccessiverecordsrangedfrom0.59to0.72(UA)andfromO.24to0.47(A)formilk,butwereintherange0to0.27(UA)or0.23(A)fortheotherthreetraits.Itwasconcludedthatfirst,unadjustedrecordscouldbeusedtocullpoorperformersformilkyield.Morerecordsweredesirableinthecaseoftheothertraitsbut,nevertheless,economicallyreasonablelimitsshouldbeestablishedoneachfarmforfirstcalfcowswithlongintervalsfromcalvingtoconception,beyondwhichtheirretentionintheherdshouldnotbeacceptable.