Impacts of genomic selection on classical genetic evaluations

Abstract : With the fast and wide development of genomic evaluations in dairy cattle, the design of breeding schemes has been modified and the long process of progeny testing is being replaced by an early and accurate genomic selection step.In the future, only selected candidates will get performances to be evaluated by the classical method of Best Linear Unbiased Prediction (BLUP). After a genomic selection step, information about the selection process is no longer complete, BLUP assumptions are violated and solutions, i.e., estimated breeding values, are feared to be incorrect.The aim of the thesis study was to consider the consequences of genomic selection on the classical genetic evaluations at the national and international levels.First, bias in national breeding values was assessed by repeated simulations. Estimated breeding values were systematically underestimated and less accurate after a genomic selection step not accounted for in genetic evaluation models.Secondly, a statistical procedure, a BLUP model with genomic pseudo-performances, was investigated to eliminate, with success, bias in estimated breeding values.In a third part, the consequences of genomic selection on international evaluations were studied by simulations. Bulls from the country sending incomplete and/or biased breeding values were the most penalized in international rankings.In conclusion, it is not only necessary but also urgent to prevent from bias in classical evaluations and therefore avoid harmful impacts on international comparisons, on future genomic evaluations, and more generally on selection efficiency. Alternative approaches were thus discussed to propose short and long term strategies for routine evaluations. Nevertheless, a main consequence of bias corrected breeding values is that all genetic predictions will include some genomic information in a near future: adaptations of evaluation methods are still required to optimally benefit from all types of information.
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Clotilde Patry. Impacts of genomic selection on classical genetic evaluations. Agricultural sciences. AgroParisTech, 2011. English. ⟨NNT : 2011AGPT0073⟩. ⟨pastel-00781220⟩

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