Pleiotropic Genes Affecting Milk Production, Fertility, and Health in Thai-Holstein Crossbred Dairy Cattle: A GWAS Approach

Genomic selection and genome-wide association studies (GWASs) are powerful tools for improving dairy cattle’s milk production, fertility, and health traits. While these methods have been successfully applied to purebred populations in the United States and Europe, their effectiveness in crossbred dairy cattle, particularly in tropical regions such as Thailand, remains less well explored. Identifying the pleiotropic genes influencing multiple economically important traits can enhance genetic selection strategies. This study evaluated the potential of weighted single-step genomic best linear unbiased prediction (wssGBLUP) to improve GEBV accuracy compared to the standard single-step GBLUP (ssGBLUP) and applied a wssGWAS to identify key genetic markers for production (305-day milk yield), fertility (days open), and health traits (fat-to-protein ratio) in Thai-Holstein crossbred dairy cattle. Further research is needed to validate these findings and optimize breeding programs for tropical dairy systems. © 2025 by the authors.