Influence of OCD on Horse Racing Starts and Earnings

It takes four to five years for a young horse’s skeleton to become completely mature, and numerous factors can cause problems before the process is finished. A foal’s size, pattern of weight gain, type and amount of exercise, feed management, heredity, and even prenatal nourishment can sidetrack the correct development of cartilage and bone.

Osteochondritis dissecans (OCD) is a type of developmental orthopedic disease characterized by defects in the process by which cartilage ossifies. Small flaps of joint cartilage can partially or completely separate from the underlying layers of tissue, leading to inflammation and lameness in young horses. Some milder cases of OCD self-correct with time and rest. In other horses, the lesions can be repaired surgically.

To find out whether young horses with OCD are as successful in their racing careers as unaffected horses, a study was conducted by researchers at the University of Illinois. The researchers collected information on 819 Standardbred yearlings born in 2005 or 2006. The same veterinarian examined fluoroscopic radiographs of each yearling’s fetlocks, knees, hocks, and stifles for signs of OCD. The number of race starts and earnings at two, three, and four years of age were recorded.

Analysis of this information showed that 462 horses did not have OCD and 357 had a lesion affecting at least one limb. Of the total sample, 597 horses started at least one race at two or three years of age. Among horses without lesions, 75% started a race compared to 70% of horses with at least one lesion that started a race. Horses without lesions had slightly more starts but the number was not significant. Horses without lesions had slightly higher average earnings at two years of age and slightly lower average earnings at three years of age; these differences were not significant.

In this study, analysis of sires and the appearance of OCD in yearlings did not show a correlation, though other studies have indicated there may be some genetic component to the incidence of developmental orthopedic disease. This study did not indicate a significant difference in race starts or earnings among yearlings that did or did not have OCD lesions. However, more than 90% of these horses that showed lesions as yearlings had corrective surgery at some later time, and it is possible that this intervention allowed them to compete on a virtually equal basis with horses that did not have lesions.