Heritability of epistaxis in the Australian Thoroughbred racehorse population.
Authors: Velie B D, Raadsma H W, Wade C M, Knight P K, Hamilton N A
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Heritability of Epistaxis in Australian Thoroughbreds Post-exercise epistaxis represents the most visible manifestation of exercise-induced pulmonary haemorrhage (EIPH) in racehorses, yet debate continues about whether genetic predisposition or environmental factors drive its expression. Velie and colleagues analysed racing records from over 117,000 Australian Thoroughbreds competing between 2000 and 2011, using logistic mixed models to partition the contribution of heritable versus non-heritable influences on epistaxis occurrence. The researchers found moderate to substantial heritability estimates—0.27 for lifetime epistaxis risk and 0.50 for risk within individual races—whilst sex, age, and year of birth emerged as significant non-genetic variables, though notably, trainer identity, jockey, race distance, track condition, racecourse, and surface type did not. These findings suggest that whilst genetic factors account for a meaningful proportion of epistaxis risk, racing management and track-specific variables appear less influential than commonly presumed, implying that selective breeding strategies warrant consideration alongside continued investigation of the physiological mechanisms underlying EIPH expression.
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Practical Takeaways
- •Epistaxis in racehorses has a heritable component (h²=0.27-0.50), suggesting selective breeding decisions could reduce incidence in populations
- •Age and sex significantly influence epistaxis risk, so management strategies should account for individual horse characteristics rather than relying solely on modifiable race conditions
- •Track and race management factors (surface, distance, going, starters) did not significantly affect epistaxis occurrence, indicating genetic predisposition may be more important than environmental race conditions
Key Findings
- •Lifetime epistaxis risk heritability was 0.27, indicating moderate genetic contribution to the condition
- •Individual race epistaxis risk heritability was 0.50, suggesting stronger genetic influence when assessed per-race
- •Sex, age, and year of birth were significant factors, while trainer, jockey, race distance, track going, and racecourse were not significant
- •Evidence demonstrates both genetic and non-genetic links contribute to epistaxis expression in Australian Thoroughbreds