The second year of a horse’s life brings significant changes not only in his development, but also in his use. Lanky yearlings, though perhaps still hip-or-wither-high, broaden and become more proportional. Fillies and stud colts show increasing sexual maturity. And, depending upon the intended discipline, an owner’s thoughts turn toward training. The changes during the 18-24-month period bring rewards, but they also carry health risks.

Ideally, a horse owner will monitor a foal’s development from birth–closely observing growth, conformation, nutrition, housing, socialization, and preventive care as discussed in the first two segments of this series (see the February and June issues). But, what about the foal purchased at a yearling sale, or one that is brought in from the yearling band to prepare for training? What should owners look for in the near 2-year-old?

Musculoskeletal Development

By 18 months, "most (orthopedic) lesions are already developed but may not yet be clinical," meaning the horse doesn’t show detectable signs of the disorder, says Elizabeth M. Santschi, DVM, Dipl. ACVS, associate professor of veterinary clinical sciences at The Ohio State University. Developmental abnormalities that might become apparent at this age include osteochondritis dissecans (OCD) lesions in the cartilage and bone of developing joints; acquired flexural deformities such as contracture of the fetlock (in which the joint can’t be fully extended); and wobbler syndrome, a malformation of the cervical vertebrae (in the neck) causing compression of the spinal cord