Genome-Wide Association Study of Leukocyte Traits Reveals Candidate Genes Associated With Immunity in Holstein Cattle From Southern China.

Leukocyte traits are crucial clinical indicators for various diseases, reflecting the immunity in dairy cows and indicating production performance and elimination rate. In Southern China, diseases caused by high temperature and humidity in summer significantly impact the production of dairy cows. Conducting a genome-wide association study (GWAS) on leukocyte counts and components in healthy individuals is essential for identifying genes involved in leukocyte production, differentiation or clearance, thereby aiding in the accurate identification of genetic sources of immune variation in dairy cows. This study measured leukocyte traits in 200 healthy dairy cows and conducted GWAS. The results revealed 70 single-nucleotide polymorphisms (SNPs). Of these, 15 SNPs were within genes and all in introns. Additionally, the BEN Domain-Containing Protein 5 (BEND5) gene, which regulates white blood cell count (WBC), percentage of basophils (%BASO) and percentage of lymphocytes (%LYMPH), and the Forkhead box J3 (FOXJ3) gene, which regulates WBC and %BASO, were identified as two crucial candidate genes. This study provides new evidence on the genetic basis of immunity differences in dairy cows in Southern China, suggesting that the SNPs and candidate genes identified could be valuable for dairy cow breeding.