The genetics of morphological traits in the grasscutter

摘要

Theobjectivesofthisstudyweretoestimatephenotypicandgeneticparametersofmorphologicaltraitsofthegrasscutter,andtofindthebestmorphologicaltraitpredictorofbodyweight.ThestudywascarriedoutatthegrasscuttersectionoftheDepartmentofAnimalScienceEducation,UniversityofEducation,Winneba,Mampong-Ashanticampus,Ghanafrom2009to2010.Datawererecordedonmorphologicalcharacteristicsandbodyweightsof116animals(66femalesand50males)selectedatrandom.Bodyweightsandlinearbodymeasurementswererecordedfortheanimalsatbirth,atweaning(2months)andat6months.nbsp;Meanbody,tailandheadlengths,heartgirthandheight-at-witherswere35.6,10.2,8.2,18.0and11.6cm,respectively.Atbirth,malesandfemaleshadsimilar(P0.05)bodymeasurementsforallthemorphologicaltraits.nbsp;However,at2and6months,maleshadsignificantly(P0.05)longerbody,headandtaillengths,largerheartgirthandtallerheight-at-withersthanfemales.Thebestpredictorofbodyweightwasheartgirth.Directgeneticdiversity(variability)ofbodylength,headlengthandheartgirthwerelowwhilstthoseoftaillengthandheight-at-withersweremoderate.Proportionofphenotypicvarianceduetopermanentenvironmentaleffectsofdam(c2)waslowtomoderate(3-23%).Covariancesbetweendirectandmaternaleffectswerenegative(-2.3to-29.2).Directheritabilityforalltraitswashigh(0.52-0.60)andmaternalheritabilitywasmediumtohigh(0.39-0.75).Correlationsbetweendirectandmaternalgeneticeffectswerehighnegative(-0.61to-0.78).Geneticcorrelationsamongmorphologicaltraitsweremedium(0.45)tohigh(0.85),whilsttheirphenotypiccorrelationswerehigh(0.71to0.90).Geneticcorrelationsbetweenbodyweightandallmorphologicaltraitswerelow(0.04to0.23),whilsttheirphenotypiccorrelationswerehigh(0.75to0.90).nbsp;Itwasconcludedthatgeneticselectionwillbeeffectiveinimprovingallthemorphologicaltraits.However,littletonocorrelatedresponseinbodyweightwouldbeexpected.Itwasalsoconcludedthatheartgirthcanbeusedbyfarmerstopredictbodyweightofgrasscutters.Itwasrecommendedthatfarmersshouldnotuseheadshapeforsexdeterminationatbirth.