NEWS NOTES

UC Davis Efforts Contribute to Continued Decline in California Racehorse Fatalities

By Amy Young UC Davis

The number of racehorse fatalities in the 2022-23 fiscal year continues to decline, according to the California Horse Racing Board (CHRB).

Fatalities have been trending downward since 2005, with the recent report totaling 26 fatalities resulting from musculoskeletal injuries that occurred while racing or training at CHRB-regulated facilities (compared with 39 the previous year). According to the CHRB, 30,000 race starts and more than 100,000 workouts occur across 8,000 to 10,000 horses annually.

Long-standing efforts between the CHRB and the UC Davis School of Veterinary Medicine have built on past successes to benefit equine welfare and safety.

From research programs to testing facilities, UC Davis is integral to advances in racehorse health and injury prevention. The school is home to the J.D. Wheat Veterinary Orthopedic Research Laboratory, where Dr. Susan Stover’s group has characterized changes in proximal sesamoid bones that put racehorses at risk for catastrophic fracture. These data, combined with standing equine positron emission tomography (PET) scanning, pioneered by at UC Davis by Dr. Mathieu Spriet, now allows at-risk horses to be identified and successfully rehabilitated for return to training and competition.

The California Animal Health and Food Safety Laboratory at UC Davis is home to the CHRB Post-mortem and the Kenneth L. Maddy Equine Chemistry Laboratory. The Post-mortem Examination Program provides necropsies (animal autopsies) for every horse that dies or is euthanized at CHRB racetracks and training facilities. The Maddy Laboratory is the CHRB’s primary drug-testing laboratory. The laboratory, which is part of the California Animal Health and Food Safety Laboratory System and is co-managed by professors Benjamin Moeller and Heather Knych, tests more than 40,000 samples from California racehorses annually.

In combination, these programs have provided valuable insights into the causes of racehorse injuries, as well as science-based approaches to improvements in injury detection and prevention.

How Common Is Sudden Cardiac Death?

Premature depolarizations occur more often among horses during cross-country competition, and those in the upper divisions were at a higher risk, according to a recent study done my veterinarians from several U.S. facilities, including New Bolton Center, in Kennett Square, Pa., and Equine Sports Medicine Consultants, in Newark, Del.

They did a prospective, cross-sectional study to determine the frequency and types of rhythm disturbances that these elite athletes suffer. They also wanted to highlight the factors for premature depolarisations occurring during the cross-country phase of United States Eventing Association (USEA) and Fédération Equestre Internationale (FEI)-sanctioned events.

They obtained continuous electrocardiographic (ECG) recordings from 75 horses prior to, during and immediately following the cross-country competition and categorized them by complexity (singles, couplets, triplets, complex).

Premature depolarizations were identified in 42 of the 75 horses (56%) during the competition. The horses competing in the upper divisions of eventing had higher odds for having any premature depolarisations during the event compared with the lower divisions (OR = 17.5 [4.3, 72.01], P=0.006).

Another factor was the time the heart rate (HR) was >199 beats per minute, which was associated with more complex arrhythmias (triplets, salvos and tachyarrhythmias) (OR = 1.01 [1.0, 1.02], P=0.005), they said.

They also found that an irregular heartbeat at rest was associated with arrhythmia in the early recovery period (OR = 3.5 [1.1, 10.8], P=0.03).

For more information:

Durando MM, Slack J, Birks E, et al. Premature depolarisations in horses competing in United States Eventing Association and Fédération Equestre Internationale-sanctioned 3-day events. E Vet J. 2023 May 30. 2023 May 30. doi: 10.1111/evj.13948. https://beva.onlinelibrary.wiley.com/doi/10.1111/evj.13948