A correct assessment of the effects that heat load has on animal performance is of main interest not only for the quantification of the losses associated to it, but also for the correct characterization of individual thermo-tolerance. The latter is key for the identification of genome regions associated with animal thermo-tolerance. In the present study, nine phenotypes have been proposed and their suitability in genome-wide studies has been investigated. Two main approaches have been considered: a first one using pseudo-phenotypes (obtained from the solutions of a mixed model including a norm of reaction to individual heat load term but ignoring pedigree relationships) as phenotypes in the GWAS studies, and a second one using deregressed proofs from those pseudo-phenotypes obtained from a single-step approach. An FDR threshold of 10% was used to select relevant SNPs. Results have shown that many of the markers bellow that threshold were associated with phenotypes representing the animal level of production and located within genome regions comprising production genes like DGAT1. However, 35 out of 95 and 42 out of 78 SNPS for fat and protein, respectively, showed a significant association with phenotypes describing production losses. The dgvGWAS approach identified more SNPs than pseudoGWAS approach for fat content, but the behaviour was different for protein, where pseudoGWAS captured a larger number of SNPs. These two traits appear to have similar heritabilities but different genetic architecture what might be behind this different behaviour. Keywords: heat stress, gwas, dairy cattle

Manuel Ramón, María J Carabaño, Clara Diaz

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Challenges - Environmental, , 831, 2018
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