Mendelian Sampling variance tests with genomic preselection

Peter G Sullivan


Interbull has introduced a new validation test, and provided corresponding software to detect non-zero time trends and outliers years, for estimates of genetic variance.  The test is applied separately for cows and AI sires, for all traits included in the Interbull MACE evaluation service.  In recent years, AI sires have been genomically preselected, using genotype-based evaluations when they were young calves.  Genomic preselection significantly changes the expectation of Mendelian sampling distributions for AI bulls.  The new Interbull test is applied to EBV computed without genotypes, which are biased by ignored genomic preselection effects.  The purposes of the present study were to apply the new validation test to Canadian data, firstly using official EBV submitted for MACE, and secondly using corrected EBV, after making adjustments to reduce preselection biases in the MS distributions of the most recent AI bulls.  For the main traits under selection in Canada, test results were a pass for official EBV, but a fail for bias-corrected EBV.  For bull populations with genomic preselection, biased EBV are expected to pass the test, while unbiased data are expected to fail.


trend validation; international evaluation; Mendelian sampling; genomics; selection bias

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