Genome-Wide Association Analyses of Osteochondrosis in Belgian Warmbloods Reveal Candidate Genes Associated With Chondrocyte Development.

Osteochondrosis (OC) is an important skeletal disease causing profound welfare concerns in horses. Although numerous studies have explored the genetics underlying OC in various breeds, the Belgian Warmblood (BW) remains unstudied despite having a concerning prevalence of 32.0%. As a result, this study aimed to conduct genome-wide association (GWA) analyses to identify candidate variants associated with OC in BWs. To achieve this, blood samples and radiographs were collected from 407 Belgian Warmbloods registered to one of two BW studbooks (Belgisch Warmbloedpaard and Zangersheide), and genotyping was performed using the 670K Axiom Equine Genotyping Array. GWA analyses using a principle component approach were then performed on OC status (OCS; presence or absence of OC at any joint), hock OC status (HOC) and stifle OC status (SOC). These analyses yielded significantly associated (P < .01) SNPs on Equus caballus chromosome (ECA) 3, ECA 12, and ECA 18 for OCS; however, no single nucleotide polymorphisms (SNPs) reached significance for HOC or SOC. Subsequent analysis of candidate genes within 500 kilobases of the significant SNPs revealed functions broadly related to cell differentiation and chondrocyte development. While this study represents another step forward in uncovering variants and biological pathways associated with OC, additional studies are needed to validate the newly identified candidate SNPs for OC in BWs. Further studies of OC in BWs, as well as other breeds, are critical in our efforts to fully understand the disease's etiopathogenesis and ultimately provide breeding programs better equipped to improve horse health and well-being.