Growth and Bone Development in the Horse: When Is a Horse Skeletally Mature?

Abstract

Within the lay literature, and social media in particular, there is often debate about the age at which a horse should be started and introduced to racing or sport. To optimize the welfare and longevity of horses in racing and sport, it is important to match exercise with musculoskeletal development and the ability of the musculoskeletal system to respond to loading. The justification for not exercising horses at a certain age is often in contrast to the scientific literature and framed, with incorrect generalizations, with human growth. This review provides a relative comparison of the growth and development of the horse to the descriptors used to define growth and development in humans. Measures of physeal closure and somatic growth demonstrate that the horse completes the equivalent of rapid infant growth by weaning (4–6 months old). At approximately 11 months old, the horse completes the equivalent of the childhood phase of growth and enters puberty. At 2 years old, the horse has achieved most measures of maturity used within the human literature, including the plateauing of vertical height, closure of growth plates, and adult ratios of back length:wither height and limb length:wither height. These data support the hypothesis that the horse evolved to be a precocious cursorial grazer and is capable of athletic activity, and use in sport, relatively early in life.

Internet Survey Evaluation of Demographic Risk Factors for Injury in Canine Agility Athletes

“…It is possible that the population of agility handlers that choose to have radiographs of their dogs made to assess growth plate closure do so in order to train harder, and at a younger age, which may be contributing to the increased injury risk. It is also possible that radiographic growth plate closure is not a good indicator of safety for increasing training intensity as it does not necessarily correlate with development and strength of the surrounding soft tissue structures, such as ligaments, tendons, and muscles, nor cartilage development (25,26). Studies focusing on sports readiness in adolescents have found that most children are ready for participation in sports by the age of 12 (21).…”

“…These studies not only consider physical aspects, but also include cognitive and psychosocial development as well, making it difficult to make any direct comparisons to our canine agility athletes. Within the equine literature, sport readiness is debated and the optimal level of exercise in young horses is unknown (25)(26)(27).…”

Influence of age and sex on bone development and athletic career longevity of Thoroughbred racehorses in Brazil - preliminary study

“…Research performed on racehorses in the UK (2) observed that 78% of fractures occurred during training, and at least 57% were stress fractures, demonstrating non-adaptation to the training regimen. Besides being a desirable feature in racing, scientific evidence suggests a positive influence of the early onset of controlled training, allowing the proper bone and cartilage adaptations to exercise (8,19,21) , resulting in longer athletic careers (22,23) . Regardless of what may be familiar to the TB horse industry, starting a racing career later in life may not diminish the rate of MS injuries.…”

“…Radiographic study of distal radius growth plate calcification is still an inexpensive and practical method for evaluating bone maturity in horses, helping to adjust individual training intensities, and preventing injuries that could otherwise compromise the athletic future of horses (3,8) . To the best of our knowledge, detailed wastage studies and career evaluations of Brazilian Thoroughbred (TB) horses have not been performed, and there is a great need to increase the welfare of horses by preventing injuries and promoting knowledge to the horse racing industry.…”

Looking back over the shoulder: New insights on the unique scapular anatomy of the tapir (Perissodactyla: Tapiridae)

“…The T. pinchaque specimens (Carlotta and Cofan; Figure 1c; Table 1) were donated to the Denver Museum of Nature and Science (DMNS) by the Cheyenne Mountain Zoo following death by natural causes, with cadaver dissections performed at the DMNS Zoology Lab. One specimen (Qadira) was considered a juvenile (5 months; Table 1); tapirs in this study are considered mature beyond 2 years of age (following the trend exhibited in equids; Rogers et al, 2021). Full skeletal maturity (full epiphyseal ossification) was achieved only in Kamal, Carlotta, and Cofan.…”