Since 1990, the California Horse Racing Board (CHRB), in partnership with the California Animal Health and Food Safety Laboratory System (CAHFS), has operated a postmortem program for all racehorses that die spontaneously or are euthanized at CHRB-regulated facilities. The program aims to: (1) identify the nature of injuries, (2) determine their causes, and (3) develop prevention strategies. Necropsies are performed by CAHFS, funded by CHRB, with transportation provided by racing associations. Regardless of cause of death, a full necropsy is conducted, including examination of all systems, and often histopathology, and ancillary testing (e.g. bacteriology, virology, parasitology, toxicology). Musculoskeletal injuries are studied in detail, including both affected and contralateral limbs, with emphasis on pre-existing lesions. Medical conditions such as colic, pneumonia, and encephalitis are also investigated. Comprehensive, user-friendly reports are provided including diagrams and photographs that are used by CHRB to inform training of equine veterinarians, trainers, officers and owners and inform fatality reviews.
As of June 2024, 7,614 necropsies have been completed. Fatalities peaked at 325 in 2006 and declined steadily to 65 in 2022–2023, with a modest rise to 87 in 2023–2024. Historically, musculoskeletal injuries accounted for 70–75% of deaths, but in 2022–2023, medical cases (52%) surpassed musculoskeletal ones (48%) for the first time. Approximately 90% of catastrophic musculoskeletal injuries in racehorses are linked to pre-existing conditions, the great majority of which are preventable with timely diagnosis.
Cardiac sudden deaths remain stable at 10–12 annually, with over half undetermined—highlighting a key challenge for the program and industry. The California experience demonstrates that a comprehensive postmortem program is essential for understanding and preventing racehorse fatalities. These findings support broader implementation, including the national necropsy program mandated by the Horseracing Integrity and Safety Authority.