Horses of any breed, size, and shape are at risk of osteochondritis dissecans (OCD), a developmental orthopedic disease, if predisposing factors are present.
For years, researchers have believed that genetics play a role in the development of OCD, and science supports this assertion. No specific genes have been identified, however. A recent study* using advanced genetic analysis techniques confirmed that multiple genes contribute to the problem, and that environment, including diet and other management practices, influences the development of OCD.
“Historically, pedigrees were examined to affirm that OCD in a certain breed had a genetic component. Now, genetic tests are available that allow scientists to rapidly analyze millions of genes at a time to identify which genes may play a role in a certain trait or condition,” explained Laura Petroski-Rose, B.V.M.S, a Kentucky Equine Research veterinarian.
Using this state-of-the-art technology, referred to as SNP chips (pronounced “snip”), researchers from the University of Minnesota attempted to pinpoint the genes involved in OCD development. They analyzed genetic material from 479 North American Standardbreds, well known for OCDs of the hock.
“This study confirmed that a large number of genes contribute to OCD, making this a â€˜polygenic/complex disease,’ and therefore explaining why it is so challenging to eradicate,” explained Petroski-Rose. “The overall heritability was estimated at 0.24 on a scale of 0 to 1, which is considered a moderate level. This means other factors substantially affect the development of this disease.”
Based on the SNP and heritability results, the researchers concluded that “it is likely that a significant portion of disease risk is due to environmental factors and/or genotype x environment interactions, which were not accounted for in these analyses.”
“Known dietary risk factors for OCD include nutritional mismanagement, such as excess energy/calories, diets low in copper, or diets with other mineral imbalances,” said Petroski-Rose.
An improved understanding of genes involved in OCD and the development of tests will facilitate early identification of affected animals.
“In turn, this will greatly influence management changes, expedite medical intervention, and improve breeding decisions,” Petroski-Rose pointed out.
In the interim, consult a Kentucky Equine Research nutrition advisor to ensure young horses receive a balanced, energy-appropriate diet.
*McCoy, A.M., E.M. Norton, A.M. Kemper, et al. SNP-based heritability and genetic architecture of tarsal osteochondrosis in North American Standardbred horses. Animal Genetics. In press.