Growth patterns, metabolic indicators and osteoarticular status in the Lusitano horse: A longitudinal study

Development of a healthy musculoskeletal system is of high concern for horse breeders and users. A longitudinal field study was performed in order to: (i) evaluate growth patterns and long-term changes on bone quality, bone metabolism, growth factors and metabolic variables in the Lusitano horse; and (ii) retrospectively assess whether these changes were related with radiographic findings regarding osteochondrosis-like lesions (OC) at the onset of training. Thirty-four Lusitano foals born and raised at four stud-farms, were periodically weighed (BW), and measured (withers height-WH) from birth to 36 months of age. On the same days, blood samples were collected for determination of osteocalcin, bone alkaline phosphatase, insulin-like growth factor I (IGF-I), leptin, insulin, glucose, parathyroid hormone (PTH), calcium, phosphorus and magnesium plasma concentrations, and quantitative ultrasound measurements were performed on the right third metacarpal bone (McIII). At the end of the study horses underwent radiographic examination of the four fetlocks, hocks and stifles. According to their radiographic status (OC negative vs. OC positive), Richards growth function was adjusted to BW and WH data. Instantaneous BW and WH growth rates (BW IADG and WH IADG) were calculated for each foal, from the resolution of the first derivative of growth models for seven age-classes. The presence of radiographic findings compatible with OC at the onset of training was associated with changes in BW and WH growth rates. Positive horses presented higher BW IADG from six to 18 months of age and lower WH IADG before 45 days of age (P马繁育者与使用者对健康肌肉骨骼系统的发育始终高度重视。本研究开展一项纵向实地调查，旨在实现两大目标：（i）评估卢西塔诺马（Lusitano horse）的生长模式、骨质与骨代谢的长期变化、生长因子及代谢相关指标；（ii）回顾性分析上述变化是否与训练初期出现的类骨软骨病（osteochondrosis-like lesions, OC）放射学表现存在关联。 本研究共纳入34匹在4个种马场出生并饲养的卢西塔诺马驹，自出生至36月龄期间，定期记录其体重（BW）与肩高（withers height, WH）。每次测量当日，采集血样以检测血浆中骨钙素、骨碱性磷酸酶、胰岛素样生长因子I（IGF-I）、瘦素、胰岛素、葡萄糖、甲状旁腺激素（PTH）、钙、磷及镁的浓度；同时对右侧第三掌骨（McIII, third metacarpal bone）开展定量超声检测。 研究结束时，对所有马匹的4个系关节、跗关节及膝关节进行放射学检查。根据放射学检查结果将马匹分为OC阳性组与OC阴性组，采用理查兹生长函数（Richards growth function）拟合体重与肩高数据。针对7个年龄组，通过求解生长模型的一阶导数，计算每匹马驹的瞬时体重生长速率（BW IADG）与瞬时肩高生长速率（WH IADG）。 研究发现，训练初期出现符合OC的放射学表现的马匹，其体重与肩高生长速率存在显著差异：阳性组马匹在6至18月龄期间的瞬时体重生长速率更高，而在45日龄前的瞬时肩高生长速率更低（P