Genomic-free EBVs computed from Single-Step evaluations as proofs for MACE in France
Abstract
In France, all dairy breeds and all traits have been evaluated unsing a Single-Step approach since April 2022. Hence, polygenic evaluations are no longer used to select bulls in this country. Furthermore, polygenic evaluations are known to be biased due to genomic preselection. With the aim of providing to Interbull partners MACE proofs that are as unbiased and as close to the national EBVs used in France for the selection of bulls as possible, genomic-free Single-Step EBVs were computed and validated for their routine submissions as proofs for MACE. Among the methods proposed by the Interbull working group for removing the genomic part from Single-Step EBVs, the most appropriate one for France was to run a BLUP evaluation using Single-Step YDs as phenotypes. Consequently, a novel pipeline was implemented to compute the genomic-free Single-Step EBVs for all traits (including milk production, fertility, longevity, calving, conformation, workability and udder health traits) and breeds (Brown Swiss, Simmental, Montbéliarde and Holstein). Then, genetic trends estimated using the EBVs resulting from the BLUP model were validated by means of the Interbull trend validation procedure, based on the analysis of within-bull yearly daughter deviations. All the traits sucessfully passed validation tests. Genomic-free Single-Step EBVs revealed a genetic gain that was intermediate between polygenic EBVs and Single-Step EBVs. The correlations between MACE EBVs based on polygenic or genomic-free Single-Step EBVs in Holstein ranged from 0.94 to 0.994 depending on the trait. In conclusion, France successfully transitioned from providing polygenic EBVs to genomic-free Single-Step EBVs as proofs for MACE for all traits and breeds.
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