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La diversité génétique à l’ère de la génomique : évolution de la consanguinité et ses conséquences dans trois races bovines laitières françaises

Abstract : Genomic selection, implemented in France since 2009, has drastically modified breeding schemes in large French dairy cattle breeds by increasing the number of candidates for selection and reducing generation intervals. The growing use of embryo transfer has also reshaped breeding schemes, intensifying the selection of dams of bulls and further reducing generation intervals. This resulted in an increased genetic gain.However, if their use is not controlled, they put the genetic diversity of these breeds at risk. This loss of diversity, characterized by an increased inbreeding, can be accompanied by inbreeding depression, a decrease in selection efficiency and a loss of adaptive potential. It is therefore essential to understand and predict the impact of these changes on genetic diversity. We studied the implementation of genomic selection and showed that this technology has led to an increase in annual genetic gain in Montbéliarde, Normande and Prim'Holstein while the loss of genetic diversity has only been accelerated in Prim'Holstein.We showed by simulations that, in the context of genomic selection, the intensive use of embryo transfer in a Montbéliarde-type breeding scheme presented a risk for genetic diversity, and that the reduction in the number of bulls in these schemes caused both a decrease in genetic gain and an acceleration of the loss of genetic diversity.In the Montbéliarde breed, inbreeding depression resulted in lower performance for five production and health traits out of six traits studied. The effects of inbreeding on these performances were very heterogeneous along the genome.Managing inbreeding and its consequences in French dairy cattle breeds requires the implementation of effective, ethical and feasible actions in the field.
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Submitted on : Thursday, March 25, 2021 - 2:20:30 PM
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Anna-Charlotte Doublet. La diversité génétique à l’ère de la génomique : évolution de la consanguinité et ses conséquences dans trois races bovines laitières françaises. Sciences agricoles. Université Paris-Saclay, 2020. Français. ⟨NNT : 2020UPASB016⟩. ⟨tel-03181150⟩

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