Aksu, Emrah2024-09-282024-09-282023-10-121049-5398https://doi.org/10.1080/10495398.2023.2267614https://hdl.handle.net/11452/45430The A2 milk marker is gaining popularity worldwide; thus, many farms plan to convert their dairy cattle herds to the A2A2 genotype. Variation in beta-casein genotypes needs to be monitored in large dairy cattle populations. Therefore we aimed to evaluate the genotypic distributions, population genetics, and diversity parameters in Holstein-Friesian cows. A total of 1200 cattle were genotyped using the Affymetrix (R) Axiom (R) array system. We performed an association analysis regarding the CSN2 genotypes and phenotypic traits, including lactation and test-day milk yield. We next evaluated the effects of the genotypes considering the genetic merit of the animals. Animals were grouped based on their PTAs for milk production, fat, protein, and daughter pregnancy rate. Thus, we tested the genotype x genetic merit interaction for significance. The A2 allele frequency is remarkably high (0.68), and the heterozygous genotype is predominant (46.25%). The marker showed intermediate variability and diversity levels, indicating a considerable frequency of the A1A1 genotype (9.33%) remains in the population. ANOVA results showed no significant association between the CSN2 genotypes and milk yield traits. A similar finding is valid for the genotype x genetic merit regarding the genomic test results. The data presented here may be helpful for further investigations and applications on A2 milk production.eninfo:eu-repo/semantics/closedAccessProduction traitsGenetic-polymorphismBreeding valueAssociationsCsn2PerformanceVariantsBlackLociLgbA2 milkCsn2 geneGenomic testHolstein cattleMilk productionScience & technologyLife sciences & biomedicineAgriculture, dairy & animal scienceBiotechnology & applied microbiologyAgricultureArticle0010842495000014116412534810.1080/10495398.2023.2267614