New Zealand enjoys a lower rate of musculoskeletal injuries among Thoroughbreds in flat racing than those reported by overseas jurisdictions, but more information is required to pinpoint the exact reasons.
A paper published this month in the journal Animals explored the incidence of veterinary events that resulted in horses failing to finish flat races in New Zealand. The authors also looked to identify risk factors for musculoskeletal injuries during racing.
Charlotte Bolwell and her colleagues noted that there was currently limited information on the types, or risk, of injuries occurring in horses in flat races around the country.
The study team used race reports and records from six racing seasons − from August 1, 2005, to July 31, 2011 − to determine why horses failed to finish.
During the six seasons, there were 188,616 race starts for 16,646 individual horses.
In all, 544 horses failed to finish, of which 177 (33%) were classed as veterinary events. Eighty-five of these 177 horses were fatalities (48%).
Of the veterinary events reported, 136 (77%) were due to musculoskeletal injury and 41 (23%) were listed as cardiac and respiratory events.
The incidence of musculoskeletal injury on race day was calculated at 0.72 per 1000 starts, whilst the incidence of cardiac and respiratory events was 0.21 per 1000 starts. The incidence of race-day injury-related fatalities was 0.41 per 1000 starts.
Of the 136 musculoskeletal injuries, 91 (67%) were reported as fractures, 10 (7%) were reported as tendon or ligament injuries, 10 (7%) were reported as lameness, and 7 (5%) were reported as soft tissue injuries. A total of 18 (13%) were undefined.
The incidence of fractures, tendon or ligament injuries, lameness, and soft tissue injuries was 0.48, 0.05, and 0.04 per 1000 starts, respectively.
The rate of musculoskeletal injuries was lower than those reported for other racing jurisdictions, the study team noted.
Recent work in Britain reported a race-day musculoskeletal injury incidence of 2.1 per 1000 starts, while research in Kentucky had shown a rate of 4.1 per 1000 starts. Similarly, the rate of injury-related fatalities during a race was lower than that previously reported in the United States (1.9 per 1000 starts) and in the UK (0.7 per 1000 starts).
The condition of the track and the distance of the race were associated with the rate of injury during New Zealand races, the authors found.
The injury rate was significantly lower on “dead” and “slow” tracks compared with “good” tracks, and was significantly greater in races of 1671 metres or more compared with races of 1200 metres or less.
The lower injury rate than overseas jurisdictions may be because of the management and training of horses in New Zealand, or differences in case definitions used in comparable studies, they said.
There may also be differences in the training programmes and racing schedules for horses in the southern hemisphere, which may have contributed to the low rates reported in the study.
The authors said it was possible that the rate of fatalities may be underestimated in the study due to the nature of data recording before 2011, after which the Racing Integrity Unit was established and took over the monitoring and management of the stipendiary steward’s reports in New Zealand.
“However, the rate of fatalities reported in this study was the same as that previously reported in a study of race-day fatalities in Victoria, Australia, a racing jurisdiction with similar structures and levels of reporting as found in New Zealand.”
The authors noted that many studies had reported associations between exercise distances accumulated in training, prior racing history and time between races, and the risk of injuries and fatalities in training and racing.
“However, these relationships are known to be complex and are likely to vary with different case definitions investigated.”
Training information was not available for the horses used in the study, with further work needed to address the relationship between exercise history and the rates of injury during racing.
They said there was a need for a collaborative approach internationally to determine regional similarities or differences that contributed to the injury rate.
Most of the musculoskeletal injuries in the study were reported as fractures, with smaller numbers of tendon and ligament and lameness and soft tissue injuries reported.
A previous study had reported 42% and 41% of retirements from racing in New Zealand were due to fracture or tendon injuries, respectively. However, that work included injuries in training, making direct comparisons difficult.
The researchers said a detailed analysis of a range of musculoskeletal case definitions was prevented in the study due to a lack of consistent reporting of veterinary diagnosis on the stipendiary steward’s reports.
“To obtain a better understanding of the injuries associated with racing in New Zealand, there is a need for greater robustness and standardisation of descriptors used to record veterinary events occurring during a race; including the site on the horse, type of injury, and location on track where the event occurred.
“This is urgently required in order to facilitate future studies to understand the characteristics of the low rate of racing musculoskeletal injuries in New Zealand.”
The study team comprised Bolwell, Chris Rogers and Erica Gee, all from New Zealand’s Massey University; and Wayne McIlwraith, from the Equine Orthopaedic Research Center at Colorado State University.
Epidemiology of Musculoskeletal Injury during Racing on New Zealand Racetracks 2005–2011
Charlotte Bolwell, Chris Rogers, Erica Gee and Wayne McIlwraith.
Animals 2017, 7(8), 62; doi: 10.3390/ani7080062