Genome-Wide Association Studies for Conformation Traits in the Turkish Holstein Cattle Population

Abstract

Background: Conformation traits (CNTs) are part of the selection goals that significantly affect cow economic efficiency, health, welfare, and productive life in the dairy industry. Aims: This study focused on a genome-wide association study (GWAS) and genetic parameters estimation for 21 CNTs, including udder, leg-foot, body, type, and final classification traits in the Turkish Holstein (THol) dairy cattle population. Methods: A restricted maximum likelihood with a univariate model including the fixed effects of herd-year-season and days in milk was used. The total dataset consisted of CNTs records and Affymetrix BovineSNP54K data for 3,008 THol cows that calved from 2019 to 2022. The gene ontology and Kyoto Encyclopedia of genes and genome pathway databases were used to assign genes to functional categories. The biological pathways were performed in BioMart databases. Results: The heritability of these 21 CNTs ranged from 0.01 (udder index) to 0.133 (udder depth). A total of 16 significant single nucleotide polymorphisms (SNP) associated with 13 CNTs was identified. Significant SNP overlap in the candidate genes, which include ITGB1, TNN, and SEMA3D, have potential for researchers and breeders for CNTs in cattle breeding. Conclusion: These results provide valuable knowledge and contribute to the elucidation of the genetic factors responsible for conformation traits in dairy cattle populations. © 2025 Elsevier B.V., All rights reserved.