Published online by Cambridge University Press: 02 September 2010
To determine a best measure for predicting genetic merit for milking and nursing ability in beef cattle, restricted maximum likelihood (REML) estimates of variances and covariances for direct and maternal effect were obtained by using pre-weaning growth records of calves at various stages after parturition until weaning in Japanese Black cattle. Data used in this study were pre-weaning growth records of 1892 Japanese Black calves obtained from the Tottori National Livestock Breeding Station covering the period from 1960 to 1985. Traits analysed were adjusted monthly weights, adjusted monthly heights and cumulative daily gains (DGs) from birth to 1, 2, 3, 4, 5 and 6 months of age. Estimates of variances and covariances were obtained by REML using the DFREML program of Meyer. Results indicate that: (1) the direct effects on pre-weaning growth of calves are the smallest at birth to 1 month of age and then increase; (2) the maternal effects of the dams are the largest for the first 2 months, and then decrease; (3) the contribution of these two effects on calf growth is reversed at 3 or 4 months of age; (4) the non-additive maternal effects exist but are small; and (5) the genetic correlations between direct and maternal effects are low for weight and cumulative DG, whereas those for height are relatively high. These results suggest that DGfrom birth to 2 months of age (DGO-2) is most influenced by the additive maternal effect. Thus, DGO-2 is concluded to be the best measure for predicting genetic merit for milking and nursing ability in beef cattle.