The genetics of equine osteochondrosis.

This research paper discusses the genetics of equine osteochondrosis, a disease that affects the joints of horses and can lead to orthopedic problems. The published data on the heritability of this disease is reviewed, and the potential for selective breeding that reduces the prevalence of the disease is considered.

Overview of Osteochondrosis

• Osteochondrosis (OC) is a disease that predominantly affects growing horses. It’s characterized by a disruption in the differentiation and maturation of cartilage. This especially impacts the fetlock, hock, and stifle joints in horses.
• Horses with osteochondrotic lesions are at a high risk of developing orthopaedic problems later in life.

Heritability of Osteochondrosis

• The article reviews existing research on the heritability estimates for OC, signifying the extent to which genetic factors contribute to this disease. Heritabilities for OC in Warmblood and Standardbred horses have been estimated between 0.1-0.4 in animal threshold models.
• The heritability estimates give an indication of the potential effectiveness of selective breeding to reduce the prevalence of OC within these horse breeds.

Horse genome and QTL

• Whole genome scans have identified 14 areas, referred to as quantitative trait loci (QTL). These areas are parts of a genome where variation can be associated with the phenotypic expression of a trait. In this case, it is OC.
• The eight most significant QTL have been further refined using dense marker maps, which provide a higher level of detail regarding these loci.
• Genome-wide association studies using single nucleotide polymorphisms (SNPs) have revealed additional QTL in Thoroughbred, Standardbred, and Hanoverian horses. These are different types of horse breeds, suggesting that the expression of OC may vary somewhat between different breeds.

Potential for Breeding Against Osteochondrosis

• Only few QTL corresponding locations have been found among the different horse breeds, suggesting that the genetic factors contributing to OC may vary between breeds.
• Next-generation-sequencing and the use of positional candidate genes may provide further insights into the genetic determination of equine OC and aid in understanding the mechanisms behind its development.
• The implementation of selection schemes based on breeding values, or even genomic selection against OC, should be considered as an option for improving equine musculoskeletal health. This could potentially lower the prevalence of the disease in the future.