Variance components and genome-wide association studies of haematological traits in Holstein cattle population from Southern China

Haematological parameters serve as indicators of an animal’s physiological and health conditions, and investigating the genetic basis of this trait also aids in breeding animals that are resistant to diseases. Cattle raised in southern China are adapted to hot and humid climates, such as disease resistance and stress tolerance. Although haematological traits are widely recognised as indicators of immune function in both humans and livestock, there is a paucity of research focusing on the haematological traits of cattle populations from southern China. In this study, we examined 18 haematological traits in 348 Chinese Holstein cattle using both single nucleotide polymorphism (SNP)-based and gene-based genome-wide association studies (GWAS). Haematological parameter analysis exhibited low-to-moderate heritability, ranging from 0.00 to 0.59. The SNP-based GWAS identified 63 SNPs associated with seven blood parameters, with the most significant SNPs identified on bovine chromosome 5 for haematocrit levels. Gene-based GWAS revealed that two genes (ATF1 and CALCOCO2) were associated with the mean corpuscular haemoglobin concentration (MCHC) trait. These genes identified in this study were found to be involved in the regulation of immune function. These findings not only provide insights into the genetic underpinnings of haematological traits in animals but also identify potential candidate genes for breeding disease-resistant cattle.