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Analyse génétique de la composition protéique & des aptitudes fromagères du lait de vache prédites à partir des spectres moyen infrarouge

Abstract : The ability of milk to be processed into cheese is closely linked to its composition, in particular in proteins. These traits, which are difficult to measure directly, were predicted from milk mid-infrared (MIR) spectra for protein composition in 3 cattle breeds Montbéliarde, Normande and Holstein (PhénoFinlait project) and for 9 milk cheese-making properties (CMP) and composition traits in Montbéliarde cows (From’MIR project). The Partial Least Squares method provided more accurate predictions than the Bayesian methods tested.A genetic analysis was performed on these traits, predicted from more than six million MIR spectra of more than 400,000 cows.Milk CMP and composition traits are moderately to highly heritable. Genetic correlations between CMP (cheese yields and coagulation) and with milk composition (proteins, fatty acids and minerals) are high and favorable.The genotypes of 28,000 cows were imputed to whole genome sequences using the 1000 bovine genome reference population.Genome wide association studies (GWAS) reveal many genes and variants in these genes with strong effects on CMP and milk composition. A network of 736 genes, associated with these traits, enable the identification of metabolic pathways and regulatory genes functionally linked to these traits.A pilot genomic evaluation was set up in Montbéliarde cows. A test-day model, including variants detected by GWAS, provides the most accurate genomic value estimates. Simulation of a selection shows that it is possible to improve the cheesability of milk with a limited impact on the genetic gain of the traits that currently make up the breeding objective.The work presented in this thesis led to 1) the detection of genes (some of which have never been described before) and candidate variants for milk CMP and composition traits and 2) the implementation of a genomic evaluation of CMP predicted from MIR spectra in Montbéliarde cows of the Comté PDO area.
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Submitted on : Friday, January 10, 2020 - 2:38:07 PM
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Marie-Pierre Sanchez. Analyse génétique de la composition protéique & des aptitudes fromagères du lait de vache prédites à partir des spectres moyen infrarouge. Génétique animale. Université Paris Saclay (COmUE), 2019. Français. ⟨NNT : 2019SACLA008⟩. ⟨tel-02434974⟩



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