Environmental and genetic effects on the temperament variability of Guzerá (Bos indicus) females

摘要

ThetemperamentofGuzeráfemaleswasevaluatedtoidentifygeneticandnon-geneticfactorsinfluencingtheexpressionofthistrait,providinginformationtosupportdecision-makinginbreedingprograms.Temperamentassessedbyreactivitywasevaluatedinalivestockscaleusingvisualscoring(TS)andanelectronicdevice(TR).Measurementswererepeatedduringtherainyanddryseasonsin1354femalesfromfiveherdscomprising2663records.Estimatesof(co)variancecomponentsandgeneticparameterswereobtainedusingthederivative-freerestrictedmaximumlikelihoodmethod.ThereactivityofGuzeráfemaleswidelyvaried.Thereisindicationthatthebullsusedintheseherdshavebeenchosenbasedalsoontheirdaughters#8217;temperament.Theeffectsofherd,season,physiologicalstate,weightclass,entryorderclass,andageattimeofmeasurementweresignificant(p0.001)sourcesofvariationinTR.Herdwasthemostimportantfactorassociatedwiththereactivityandparticularlyhandlingpracticesarelikelytoexplainthedifferences.TheheritabilitiesofTSandTRwereestimatedas,0.29±0.08and0.06±0.02,respectively.Thegeneticcorrelationswere0.89betweenTSandTRand-0.46betweenTRandtest-daymilkproduction.ThisstudysuggestedthatvariationinTRismainlyinfluencedbynon-geneticeffects.GeneticparameterestimatesstilldonotallowforanaccurateestablishmentofthepotentialofTRforselection.Furtherstudiesusinglargerdatasetsshouldbeperformedtoprovideadditionalevaluationoffemaletemperament.