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

Abstract The impact of high-speed exercise on the musculoskeletal system of young racehorses has been extensively discussed because of concerns regarding animal health and welfare. This study investigated the correlation between age, degree of ossification of the distal radial epiphysis, sex, and career longevity of Thoroughbred racehorses in Brazil from 2012 to 2015. We performed a retrospective evaluation of 286 dorsopalmar radiographs of the left radiocarpal region of young horses and their racing performance. Distal radial epiphyseal closure was classified into three degrees: A, B, or C. Performance data included the number of races raced, athletic career length, and the number of races per month. The variables were subjected to regression analysis. At the time of radiographic examination, male horses were significantly older than females, and horses with epiphyseal closure degrees differed with age. Age at first race was 33.08±3.81 months, the average of races raced was 18.32±15.14 races, athletic career duration was 20.37±13.82 months, and the number of races raced per month was 0.93±0.46 races. Age influenced (P>0.001) the distal radial epiphyseal closure on racehorses, but sex did not (P=0.218 for males and P=0.275 for females). An inverse association was observed between age at the first race, the number of races raced per month, and athletic career duration. The frequency of race and the age at the first race influenced athletic career duration.

摘要 由于动物健康与福利层面的顾虑，高速运动对年轻竞赛马肌肉骨骼系统的影响已被广泛探讨。本研究针对2012至2015年巴西境内的纯血竞赛马（Thoroughbred racehorses），调查其年龄、桡骨远端骨骺（distal radial epiphysis）骨化程度、性别与职业生涯时长之间的相关性。我们对286例年轻马左侧腕桡关节区域的背掌位X光片（dorsopalmar radiographs）及其竞赛表现进行了回顾性评估。桡骨远端骨骺闭合情况被划分为A、B、C三个等级。竞赛表现数据涵盖参赛总次数、运动生涯时长以及月均参赛次数。对各变量开展了回归分析（regression analysis）。在X光检查时，公马的年龄显著大于母马，且不同骨骺闭合等级的马匹年龄存在差异。首赛年龄为33.08±3.81月龄，平均参赛总次数为18.32±15.14次，运动生涯时长为20.37±13.82月龄，月均参赛次数为0.93±0.46次。年龄对竞赛马的桡骨远端骨骺闭合情况存在显著影响（P>0.001），但性别无此影响（公马P=0.218，母马P=0.275）。研究发现首赛年龄、月均参赛次数与运动生涯时长呈负相关关系；参赛频率与首赛年龄会对运动生涯时长产生影响。