Horses naturally run, but not at sustained speeds over the distances and obstacles in modern racecourses. Commercial races can be dangerous and exhausting for horses. As Mundy  puts it, “Consider a 1,000-lb horse traveling at speeds of more than 25 mph suspending its entire weight (a force approaching 1 ton) on a single limb. It’s no wonder the lower limbs of horses are susceptible to sprains, strains, and fractures.” A large-scale study of over 35,000 race starts found 3.3 horse injuries, of which 1.4 were fatal, for every 1,000 starts . In New Zealand, the rate of failure to complete is around 2.88 per 1,000 horse starts .
Thoroughbreds are commonly raced in New Zealand, even though Mundy  notes that “Thoroughbreds … appear to be at particular risk for injury …” A range of other factors may also increase injury risks, including race type, number of horses and crowding. Jump races are particularly dangerous for horses, and the Melbourne Cup and similar high stakes races are extremely exhausting, and regularly result in deaths.
Veterinarians may be present, but as Mundy  notes, “Acute injury management expertise, equipment, and procedures vary among racetracks.” Unfortunately, because of their body weight, treatment of horses with lower limb fractures is extremely difficult, and such horses are often euthanased trackside. Many horses have been killed at New Zealand racetracks in recent years.
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2. Peloso JG, Mundy GD and Cohen ND. (1994). Prevalence of, and factors associated with, musculoskeletal racing injuries of Thoroughbreds. J Amer Vet Med Assoc, 204, 620–626.
3. Tanner J, Rogers C, Bolwell C, et al. (2016). Analysis of failure to finish a race in a cohort of thoroughbred racehorses in New Zealand. Animals 6(6), 36.