Genetic parameter estimates for weaning traits in a multibreed beef cattle population

[摘要] ENGLISH ABSTRACT: The aim of this study was to estimate genetic parameters as well as to evaluate theinfluence of some genetic factors on preweaning growth traits in a multi breed beef cattlepopulation. These preweaning growth traits were birth weight (BW), weaning weight(WW) and average daily gain (ADG). Three aspects were addressed in this particularstudy; namely the Estimation of (co)variance components and genetic parameters, theeffect of sire breeds and dam genotypes and the contribution of Charolais and Angusbreeding levels on weaning traits in a multibreed beef cattle herd.Variance components and resulting genetic parameters of BW, WW and ADG in thepopulation were estimated by Restricted Maximum Likelihood (REML) procedures. Fourdifferent unitrait and multitrait animal models were fitted ranging from a simple modelwith the animal direct effects as the only random effect to the model allowing for bothgenetic and permanent maternal environmental effects. The model that included directgenetic and permanent maternal environmental effects generally best described the dataanalysed. The simple model ignoring maternal effects most likely inflated directheritability estimates. Direct heritability estimates were 0.11, 0.19, and 0.15 for BW,WW and ADG, respectively, fitting a multitrait model that comprised of both the geneticand maternal environmental effects. Under this comprehensive model, maternalheritabilties were low under both analyses, ranging from 0.02 to 0.10. Permanentmaternal environmental effects were more important than maternal additive geneticeffects for WW and ADG. Direct and maternal genetic correlations range from 0.42 to0.44 for BW, -0.22 to -0.25 for WW and -0.17 to -0.23 for ADG, while the correspondingestimates ofunitrait analysis varied from 0.58 to 0.61 for BW, -0.43 to-0.53 for WW and-0.49 to -0.79 for ADG.The effect of Charolais and Hereford sires and dam breed genotypes on BW and WW incalves of Hereford, F I, two and three breed rotational as well as terminal crosses amongthe Charolais, Hereford, Angus and Bonsmara breeds were investigated. BW and WW ofthe Charolais sired calves were significantly (P

[发布机构] Stellenbosch University