By: Dr. Lydia Gray, SmartPak Medical Director/Staff Veterinarian
OCD stands for osteochondritis dissecans and, like osteochondrosis (OC), is a type of growth disturbance of horses that falls under the general heading Developmental Orthopedic Disease (DOD). Specifically the two terms refer to bone diseases of young horses in which cartilage fails to mature properly. Although the terms OCD and OC are often used interchangeably, osteochondritis dissecans is a more advanced form of osteochondrosis where the abnormal joint cartilage actually develops cracks and fissures. Abnormal cartilage that becomes loose in the joint is commonly referred to as "joint mice."
Bone growth disorders in young horses have many overlapping causes. Genetics, growth rate, type and amount of feed, excesses and deficiencies of nutrients, too much or too little exercise and other factors can all lead to abnormal development of cartilage and bone. Although high protein diets do not appear to be a factor, excess energy intake and improper amounts and ratios of minerals have been shown to affect the health of maturing bone and cartilage in horses through four years of age. However, because most joints, like the hock and stifle, "close" long before this, weaning is considered to be the "age of no return" for preventing OCD lesions.
Sustained, modest growth rates in young horses are thought to minimize OCD-type lesions. Feeding for uniform weight gain throughout a young horse's life-especially through the critical weaning period-may reduce the chances of developmental orthopedic disease like osteochondritis dissecans. In addition, ensuring the appropriate calcium to phosphorus ratio and supplementing with copper during pregnancy may also help prevent OC, OCD and other growth disturbances.