More focus on training practices for two-year-old Thoroughbreds is required, according to researchers, who found they were more at risk of musculoskeletal injuries than their older counterparts.
It is possible that early training exercise may decrease the risk of such injuries, researchers in the University of Queensland study reported in the open-access journal, Animals.
The publication of the research by Dr Kylie Crawford and her colleagues, who delved into the incidence and type of musculoskeletal injuries in Thoroughbreds in Queensland, comes just days after the tragic death of the Epsom Derby winner Anthony Van Dyck from a broken leg in the Melbourne Cup. He is the seventh horse to have died in the last eight Cup races.
The study team said musculoskeletal injuries remain a concern in racing, involving serious ethical and welfare issues.
For their research, the study team set out to determine the incidence of such injuries for two-year-old Thoroughbreds and their older counterparts, and whether this was affected by training track, season, or rainfall.
The researchers also wanted to determine the types of musculoskeletal injuries affecting these horses, and whether they went on to trials or races after their injury.
The information needed for the study was collected through personal structured weekly interviews with participating trainers, all based in the Brisbane area, over a 13-month period.
In all, 27 trainers participated. The average number of Thoroughbreds in training each week across all trainers was 544.
A musculoskeletal injury was defined as any clinically relevant injury to the musculoskeletal system, incorporating orthopaedic and soft tissue injuries, that prevented the horse from training for seven days.
The authors found that the incidence of musculoskeletal injuries among the horses was low, with 0.6% of animals in training each week suffering a musculoskeletal setback.
The incidence of such injuries was higher among the two-year-olds than the older horses.
The authors also found differences between the types of musculoskeletal injuries in each age group.
A larger proportion of the two-year-olds had dorsal metacarpal disease and traumatic lacerations than their older counterparts.
In contrast, a smaller proportion of the two-year-olds had suspensory desmitis, superficial digital flexor tendonitis, proximal sesamoid bone fractures, and fetlock joint injuries than older horses.
12 horses lost during study period
Training track and rainfall did not affect the incidence of injuries, they reported.
The season affected the incidence of injuries among the two-year-olds, but not in the older horses.
The researchers recorded a total of 202 musculoskeletal injuries affecting 195 horses during the 13-month study. Ninety-seven of these 195 horses (50%) were older than two years, and 98 were two-year-olds.
Seven horses (4%) experienced a second such injury during the study period.
The researchers found that, despite the low incidence of musculoskeletal injuries in the study, the consequences for affected horses were severe.
In fact, 12 of the 195 horses — that’s 6% — were euthanised or died. During the study period, a total of 14 horses died among the 195 horses, meaning just two of the 14 deaths were a result of other causes.
“In this study, 11 horses were euthanised on humane grounds due to the severity of the injury and poor prognosis deemed by the attending veterinarian or consulting specialist surgeon.” One horse died as a result of a traumatic head injury, they noted.
Of the 195 horses with injuries, 82 (42%) did not a trial or race again after their injury, as determined in follow-up inquiries up to 23 months after injury.
Two-year-olds were more likely to trial or race after such injuries than older horses (79%, compared with 37% for the older horses).
The type of injury also significantly affected whether horses trialed or raced again after injury.
Horses were more likely to trial or race after dorsal metacarpal disease and traumatic injuries and less likely to trial or race after suspensory desmitis, superficial digital flexor tendonitis, and proximal sesamoid bone fractures.
Season a factor in young horse injury rate
Discussing their findings, the researchers noted that seasonal variation strongly affected the number of musculoskeletal injuries in two-year-olds, with such injuries being three times more likely in the summer than the winter. This was not the case in older horses.
They hypothesised that the poorly adapted bones of two-year-old horses may be less resilient to the firmer track conditions in the summer, noting also that two-year-olds were experiencing a rapid increase in training intensity in the summer, whereas older horses were not.
The researchers said the incidence of musculoskeletal injuries in the studied horses was low when compared with other studies on the subject. The reasons warrant further investigation, they added.
Given the difference seen between younger and older horses in terms of the types of musculoskeletal injuries, the outcome, and the risk factors, future investigations should address these different populations separately, the study team said.
“A particular focus on two-year-old training practices is required since they are at higher risk of musculoskeletal injuries.”
They continued: “Thoroughbred racing is a highly contentious, high profile and lucrative industry and, as such, attracts significant media and public opinion.
“It is vital that the industry is focused on understanding and mitigating the risks of musculoskeletal injuries.”
The authors noted the level of enthusiasm and commitment among the trainers who chose to take part in the study.
The full study team comprised Kylie Crawford, Anna Finnane, Solomon Woldeyohannes, Nigel Perkins and Benjamin Ahern, all with the University of Queensland; Ristan Greer, with Torus Research; and Clive Phillips, with Curtin University in Perth.
Crawford, K.L.; Finnane, A.; Greer, R.M.; Phillips, C.J.C.; Woldeyohannes, S.M.; Perkins, N.R.; Ahern, B.J. Appraising the Welfare of Thoroughbred Racehorses in Training in Queensland, Australia: The Incidence and Type of Musculoskeletal Injuries Vary between Two-Year-Old and Older Thoroughbred Racehorses. Animals 2020, 10, 2046.