Sudden cardiac death is an important cause of exercise-associated fatalities in Thoroughbred racehorses. Equine cardiac deaths share similarities with fatalities in human athletes that result from inherited cardiac disease. While researchers have postulated genetic causes in horses, these have not been confirmed, and heritability of sudden cardiac death has not previously been estimated in Thoroughbred racehorses. This retrospective case-control study aimed to determine the heritability of sudden cardiac death in a sample population of Thoroughbred racehorses.
Research on Sudden Cardiac Death in Racehorses
Researchers reviewed steward and post-mortem reports of Thoroughbred racehorses in Australia between 2007 and 2020 to identify horses with sudden cardiac death. They randomly selected control horses from races in which sudden cardiac death occurred or from races on the date of the case fatality. Researchers collected a five-generation integrated pedigree chart for each horse. They obtained estimates of heritability using an animal model in the ASReml-R program with variance components estimated assuming sudden cardiac death was normally distributed, and on the logit transformed scale. Inbreeding coefficients were calculated, and the risk of producing sudden-cardiac-death-affected progeny was calculated for stallions that sired ≥ 5 individuals in the case-control population.
The researchers identified 93 horses with sudden cardiac death and 465 control horses. Heritability on the underlying scale was 0.15 ± 0.09 (logit animal) and 0.24 ± 0.12 (normal animal). Inbreeding coefficients were not significantly different between groups. Of the 16 first-generation sires that appeared ≥ 5 times in the case-control data set, two sires more frequently produced affected progeny (OR 7.95–10.41).
Bottom Line
The heritability of sudden cardiac death in this population was relatively low. However, individual stallions appear more likely to produce affected progeny.
https://beva.onlinelibrary.wiley.com/doi/full/10.1111/evj.14130
Related Reading
- Practical Field Cardiology for Horses
- Research Spotlight: Sudden Death in Horses
- Sudden Death in Racehorses
Stay in the know! Sign up for EquiManagement’s FREE weekly newsletters to get the latest equine research, disease alerts, and vet practice updates delivered straight to your inbox.
