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Approximate prediction error covariances among estimates of random regression coefficients for direct genetic effects were obtained for two beef cattle data sets using an extension of the method of Graser and Tier (1997). From these, approximate accuracies of breeding value estimates for birth, 200 day, 400 day and 600 day weight were calculated. Corresponding 'exact' values were determined from the inverse of the coefficient matrix in the mixed model equations (MME), estimating the diagonal blocks of the inverse pertaining to random regression coefficients using Gibbs sampling. Approximate and 'exact' values were contrasted with empirical accuracies, obtained as correlations between true and estimated genetic values in a simulation study. Results showed good agreement between approximate and 'exact' values. |
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