Estimation of additive, maternal and non-additive genetic effects of preweaning growth traits in a multibreed beef cattle project |
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| Authors: | Mahmoud ABDEL-AZIZ Stephan Johannes SCHOEMAN Gail F JORDAAN |
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| Institution: | Department of Animal Production, Faculty of Agriculture, Alexandria University, Egypt and;Department of Animal Sciences, University of Stellenbosch, South Africa |
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| Abstract: | Data from purebred and crossbred calves, consisting of Afrikaner (AF), Charolais (CH), Simmental (ST) and Hereford and Aberdeen Angus combined (HA), were analyzed to estimate breed additive effects, breed maternal effects, average individual heterosis and average maternal heterosis. The traits studied were birthweight (BW), weaning weight (WW) and preweaning average daily gain (ADG) (kg). A multiple regression procedure was used for the estimation of these genetic effects and for predictions for breed crosses that were not included in the data set. Crosses containing higher proportions of CH or ST were heavier at birth and weaning than the other crosses and purebreds. The direct effects of BW were negative and significant (P < 0.05), except that of the CH, which was the highest. The regression coefficients were ?24.87, ?18.16, ?22.80 and ?27.02 for AF, CH, ST and HA, respectively. The maternal effects were not significant. Both average individual and average maternal heterosis regression coefficients were also not significant for BW. Regression coefficients of both direct and maternal effects for WW were not significant and were characterized by large standard errors. Average individual heterosis and average maternal heterosis regression coefficients were, however, significant (P < 0.01) and the values were 5.34 and 2.19, respectively. A similar pattern was observed for ADG, except for the regression coefficients of the maternal effects, which were significant, with larger estimates for AF and ST reflecting their superior mothering ability. The values were 0.01, 0.13, 0.13, 0.03; ?0.82, ?0.85, ?0.85, ?0.81; 0.03 and 0.01 for direct effects and maternal effects of AF, CH, ST and HA; and average individual heterosis and average maternal heterosis, respectively. Means and standard errors of purebreds and their F1 crosses not included in the dataset were predicted. |
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| Keywords: | additive genetic effects multibreed beef cattle non-additive genetic effects regression coefficients |
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