Q: People say horses don’t stop growing until they’re seven years old. If this is true, should we be riding them when they’re four?
Asked by Sami Francis
A: The age that a horse stops growing varies, depending mainly on his breed. Thoroughbreds, for example, tend to mature much faster than larger, heavier Warmbloods, and as such, can more safely be ridden at a younger age. Most horses reach 90% of their adult height and 75% of their adult weight by two years of age. After that point, it then takes about another two years for the rest of the body to finish growing. There are always exceptions to this rule, however, and some breeds may not reach full adult height until they’re seven or eight, so check with your vet first if you are uncertain.
More important, however, than the horse’s outside appearance, is his level of skeletal maturation. Growth plates are found above and below joints and calcify to lengthen the bone. These growth plates ‘close’ (become fully calcified) in a staggered sequence up until five-and-a-half years of age, but this may be later in heavier breeds. The first plates to close are in the legs, whereas the spinal plates close last.
Most vets agree that we don’t have to wait for complete closure of the growth plates before riding our young horses, though. On average, leg growth plates are closed by three-and-a-half years old, which is when a lot of horses start ‘proper’ work. It is advisable to avoid strenuous exercise, such as collected work or jumping until they’re older, but light work should not be an issue. Collected work and jumping should ideally be delayed until the growth plates in the spine and neck have closed, and the joints are stronger and more supported.