Estimates of direct and maternal (co) variance components of growth traits in Boran cattle
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Haile-Mariam, M. and Kassa-Mersha, H. 1994. Estimates of direct and maternal (co) variance components of growth traits in Boran cattle. 1-13.
Permanent link to this item: http://hdl.handle.net/10568/66794
Birth (BW), weaning (WW) and yearling weight (YW) data of Boran cattle from Abernossa ranch of the Ministry of Agriculture of Ethiopia were analysed to estimate genetic parameters due to maternal and direct effects. In the univariate analysis, six different models ranging from the simple animal model (model 1) to a model, which included direct and maternal, genetic effects and their correlation and permanent environmental effects (model 6) were applied. After comparing the Log likelihood values, model 4, which included direct and maternal genetic effects and their correlation for BW and model 6 for WW and YW-were selected as being appropriate. For BW, a direct heritability (hd2) of 0.24 and a maternal heritability (hm2) of 0.08 were estimated. In the case of WW and YW, the estimates were 0.29 and 0.34 for hd2and 0.06and0.05 for hm2, respectively. The ratios of permanent environmental variance to total (c2) were 0.14 and 0.05 for WW and YW, respectively. Estimates from the bi- and tri-variate analyses were similar to those from univariate analysis, but the estimates for hd2 were relatively higher. Particularly parameter estimates based on WW and YW together, as well as the trivariate analyses appeared to have accounted for selection bias on WW and thus resulted in a higher hd2 estimate for YW .The across trait correlation estimates were low to medium with the exception of high direct genetic and permanent environmental correlations between WW and YW. Generally, parameter estimates of Boran cattle were within the range of those for other breeds. However, the genetic antagonism between direct and maternal effects seems to be stronger (-0.33 to -0.68).