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Osteochondrosis in Young Horses: Genetics or Nutrition?By Kentucky Equine Research Staff · August 11, 2016

For decades, researchers have tried to pinpoint the cause of osteochondrosis (OC) in horses. Why the concern? OC remains an important cause of joint swelling, lameness, poor performance, wastage, and economical losses throughout the equine industry, including young Thoroughbred populations.

“OC occurs when the articular cartilage that lines the ends of long bones fails to mature into sound bone early in a horse’s life, a process referred to as endochondral ossification,” explained Kathleen Crandell, Ph.D., a Kentucky Equine Research (KER) nutritionist.

Despite the volumes of research on this important topic, conflicting data continue to be published, leaving researchers, veterinarians, and horse breeders uncertain as to the most important cause of OC. As succinctly described in a recent article*, what is known is that OC is multifactorial, involving nutrition, conformation, body size, trauma, and genetics.

To help clarify the OC situation, one group of Australian veterinarians recently reviewed radiographs (X-rays) of 1,962 Thoroughbred yearlings, identified the presence and location of OC lesions, and measured the “heritability” of OC by reviewing each affected yearling’s pedigree. Key findings of the study were:

  • Overall, OC was identified in 23% of included horses;
  • OC was found in 10% of stifle joints, 6% of hock joints, and 8% of fetlock joints; and
  • Heritability estimates for OC were low (ranging from 0 to 0.2 on a scale of 0 to 1), suggesting that only a proportion of OC cases in Thoroughbreds are heritable.

While genetics may still play a role in OC, these data suggest that nongenetic factors have a substantial influence on most OC lesions. In fact, one of the most important determinants of OC in this study was dam environment.

According to Russell and colleagues, “…breeding and farm management practices (e.g., feeding) or other factors such as parity or age of mares may be related to likelihood of osteochondrosis and could potentially be used to alter the prevalence of osteochondrosis lesions in the Thoroughbred.”

“These data support other studies suggesting that mare nutrition plays an important role in foal health,” relayed Crandell.

Ensuring mares maintain a healthy body condition score before, during, and after pregnancy and lactation; avoiding micronutrient imbalances (including deficiencies and excess), and avoiding foal overnutrition all help minimize the occurrence of OC.

Consult with an equine nutritionist today to maximize your mare’s diet.

*Russell, J., O. Matika, T. Russell, et al. Heritability and prevalence of selected osteochondrosis lesions in yearling Thoroughbred horses. Equine Veterinary Journal. In press.