Biomarkers again linked to higher injury risk among Thoroughbreds

Justify led from wire to wire to win the Belmont Stakes at the weekend. © Elsa Lorieul
“Environmental factors, particularly training track surface, are proposed as an underlying cause of the identified difference in bone metabolism between North American and Polish racehorses.” © Elsa Lorieul

Two biomarkers in serum have again been linked to a heightened risk of musculoskeletal injuries in Thoroughbreds, highlighting their potential to identify at-risk racehorses.

Musculoskeletal problems are common among racehorses, with orthopaedic injuries responsible for nearly 70% of lost training days in Thoroughbred racing. Their impact on horse welfare and racing economics are key drivers for improved measures of injury diagnosis and prevention.

Serum biomarkers of bone and cartilage metabolism have previously shown promise in predicting musculoskeletal injuries among horses.

Researchers Agnieszka Turlo, Anna Cywinska and David Frisbie set out to re-evaluate the potential usability of predictive serum biomarkers identified in North American Thoroughbred racehorses in a geographically distinct group of Polish Thoroughbreds.

Their study, reported in the journal BMC Veterinary Research, involved 26 two-year-old Polish racehorses under the care of three different trainers. They were trained and raced on turf, with training occurring six days a week.

The horses were free of lameness, had no history of musculoskeletal injury, and did not show any abnormalities in routine blood analysis at the start of the study.

The research focused on three months of training.

Blood samples were collected at the start of the study for baseline data, then at one-month intervals during the three months of training, followed by a further sample one month afterwards.

Serum concentrations of bone and cartilage biomarkers were assessed: osteocalcin, c-terminal telopeptide of type I collagen, total glycosaminoglycans (GAG), chondroitin sulfate epitope and c-propeptide of type II procollagen (CPII).

Horses were considered injured if they showed clinical signs requiring veterinary attention and leading to the loss of more than five consecutive training days on the recommendation of a veterinary surgeon.

Six of the horses fell into this category, all injured in the third month. A further two did not complete the three months due to poor performance unrelated to lameness.

The remaining 18 completed the three months of training without clinical injury, but two were injured very shortly after the completion of the three months. They were therefore classified as injured for the purpose of the study.

The researchers used matching archival data from 35 2-year-old North American racehorses in their efforts to identify universal predictors of injury.

Average levels of total glycosaminoglycans and c-propeptide of type II procollagen were found to be lower in the injured Polish group when compared to the controls, which is consistent with previous findings in racehorses.

“These biomarkers were also identified as predictors of injury in the mixed population model,” they reported.

Population origin had no significant effect on the predictive value of the evaluated biomarkers.

The researchers also found decreased osteocalcin and increased c-terminal telopeptide of type I collagen levels in the injured horses when compared to the controls.

“It suggests that balance of bone synthesis and resorption in those individuals was disrupted, leading to loss of bone mechanical resistance and subsequent stress injury,” they said. “None of these changes were reported in North American racehorses.”

They continued: “Changes in serum glycosaminoglycans and c-propeptide of type II procollagen in racehorses at risk of injury appear to be similar across distinct populations while dynamics of serum bone marker is more population-specific.”

The study team said the results had been expected to reveal how environmental differences may affect biomarker performance as an injury predictor.

“Although serum biomarkers show promise as a potential screening tool for identification of horses at risk of developing injury, further examination with well-recognised diagnostic methods is necessary in order to determine specific pathology type and location.

“Varied results in bone marker dynamics between distinct racehorse populations suggest that, as an indicator of bone metabolism, serum biochemical marker data should be used in conjunction with clinical examination and diagnostic imaging for more meaningful results.”

The trio concluded: “This study shows that racehorses in European training systems, represented by the Polish population sample, might be more prone to disruption of bone turnover homeostasis that is reflected by differences in bone marker serum levels.

“Environmental factors, particularly training track surface, are proposed as an underlying cause of the identified difference in bone metabolism between North American and Polish racehorses.

“Conversely, cartilage markers appear to show similar dynamics in injured and healthy racehorses regardless of population origin and turn out to be more accurate predictors of approaching injury.”

Turlo and Cywinska are with the Warsaw University of Life Sciences in Poland; Frisbie is with Colorado State University.

Revisiting predictive biomarkers of musculoskeletal injury in thoroughbred racehorses: longitudinal study in polish population
Agnieszka J. Turlo, Anna Cywinska and David D. Frisbie
BMC Veterinary Research 2019 15:66

The study, published under a Creative Commons License, can be read here

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