BIONÆR-Bionæringsprogram

Traditional lameness examination is based on the attending veterinarians subjective assessment of the horses movement pattern, recognizing movement asymmetry, which is especially challenging when the horse is moving at high speed. Subjective lameness evaluation may be aided by objective, sensor-based technology systems, which with unparalleled accuracy measure movement asymmetry. Previous studies have demonstrated that most riding horses in regular training move asymmetrically; however, knowledge is lacking regarding the biologic and clinical relevance of this finding. Especially challenging is the distinction between movement asymmetry due biological variation, versus movement asymmetry due to a clinical (painful) condition. Also, knowledge is scarce regarding the development of movement asymmetry over time, in relation to clinical lameness. Expanding the scientific knowledge base regarding these matters may result in earlier detection of clinical lameness, which in time, will improve animal welfare for horses affected by orthopedic conditions. The objective of this prospective longitudinal study was to investigate the prevalence and magnitude of movement asymmetry using an objective sensor-based system, in a large group of young Standardbred trotters. Horses were recruited as yearlings as they were introduced to training, and the 2-year study period lasted until the end of their 3-year old season; a total of 114 horses from 13 different training yards in Norway and Sweden were included. Movement asymmetry was measured at the trot, both during in-hand trot-ups and while driving, using a commercially available inertial measurement unit (IMU) system: IMU sensors are placed directly onto anatomical landmarks on the horse, and sensor data output is processed by purpose built software calculating movement asymmetry of the horse. Data was collected approximately every 3 months, resulting in a total to 8 data collection yard visits. For the first data collection visit, 94% of included horses demonstrated movement asymmetry exceeding the threshold values recommended by the system manufacturer; however, mild asymmetry was found in most horses. There was considerable variation in this data, reflecting typical youngster behavior, and the fact that horses were just introduced to any meaningful training. When comparing asymmetry data from the in-hand trot-ups to the driven exercise, no group-level differences were found, however, there were large individual variations; some horses even changed their asymmetry pattern between trotting in-hand and while being driven. This finding supports the current recommendation of assessing harness racehorses both in-hand and while driven on a track when assessing for lameness. Throughout the two-year study period, substantial movement asymmetry (exceeding threshold values) was found in included horses. Most horses demonstrated mild asymmetry, whereas a smaller proportion of included horses had moderate to severe asymmetry. Over time, there was a trend of increasing severity of hind limb asymmetry at a group level; however, this finding must be interpreted with care as a large number of horses left the study during the study period due to re-location, lameness, or other issues precluding continued training. Therapeutic joint injections were the most common orthopedic treatment registered during the study period, and was most frequently administered in the 3-year old season. The vast majority of horses finishing the study period received such treatment in one or multiple joints. Regardless, >70% of the study subjects started qualifying races within their 3-year old season, and 64% raced in registered tote races, which is a larger proportion than the national average for 3-year olds. One potential explanation for this is the fact that only horses from professional trainers were recruited to the study.

Resultater fra studien viser at bevegelsesasymmetri er svært vanlig forekommende hos unge varmblodstravere, allerde fra de settes i trening som åringer, og i økende omfang til de er på slutten av sin 3-års sesong. Dette er potensielt svært viktig med tanke på dyrevelferden i travsporten, som har som et grunnpremiss at hester som stiller til start skal være friske og uhalte. Det neste viktige steget i denne forskningen er dermed å gå grundigere inn på årsaksfaktorer rundt bevegelsesasymmetri i en slik type hestepopulasjon. Datagrunnlaget fra denne studien er således den første byggesteinen i et større arbeide angående dyrevelferd i travsporten.

Many horses in training show motion asymmetries, but it is not known if these are due to pain caused by training; or due to individual biological variations. The aim of this project is to initiate three cohort studies where changes in motion symmetry will be monitored over time in riding horses and trotters. The prevalence and degree of motion asymmetry will be studied in young horses before and after training is initiated and in adult riding horses competing on advanced level. The project will give us important information on when asymmetries arise and how they develop over time. If horses have mild motion asymmetries that do not change over time, with different types of training, this could indicate natural persistent asymmetries. The proposed study is also highly useful for future studies where detailed information on training and management may lead to identification of risk factors for development of orthopedic lesions and improve interpretation of clinical use of motion symmetry.