The aim of the study is to identify age-related morphological features of the thoracic limb bones in horses. Data from outpatient journals at large equestrian farms in Krasnoyarsk Region and the Republic of Khakassia were analyzed. Cadaveric material from the thoracic limbs of horses aged 9 months, 1.6 years, and 14 years was examined using radiography, osteometry, and macro- and micromorphology. It was found that the average incidence of musculoskeletal injuries in horses at several farms in Krasnoyarsk Region and the Republic of Khakassia was (27.43 ± 2.77)%. One of the reasons for this high injury rate may be incomplete osteogenesis in horses entering service. Thus, in foals and horses entering puberty, the scapula, humerus, radius, and ulna continue to grow intensively; their linear dimensions increase due to unclosed growth zones with metaepiphyseal cartilage. The bones of foals and horses at puberty have smooth, even edges and surfaces, without additional roughness, tubercles, or ridges. In horses of reproductive age, growth zones are absent. The bones are tuberous, rough, and ridged, with fusions present: the ulna to the radius and the medial splint to the third metacarpal. Thus, in horses, the bones of the distal thoracic limb—the phalanges, metacarpals, and carpus—complete their growth earliest, as they show no significant differences across age groups and exhibit ossification of the metaepiphyseal zones and formed lamellar bone tissue. Osteon lamellae, intercalated lamellae, and osteocytes with cytoplasmic processes are clearly visible within this tissue.
Undraytis et al. (Fri,) studied this question.