Marginal ancestral contributions to atrial fibrillation in the Standardbred racehorse: Comparison of cases and controls.
Authors: Kraus Megan, Physick-Sheard Peter, Brito Luiz F, Sargolzaei Mehdi, Schenkel Flávio S
Journal: PloS one
Summary
Atrial fibrillation in Standardbred racehorses has become increasingly common since the 1990s, yet despite modest heritability estimates (approximately 0.15), the specific genetic architecture underlying susceptibility remains poorly characterised. Kraus and colleagues used pedigree analysis to compare the ancestral contributions of 168 affected horses admitted to Ontario Veterinary College Teaching Hospital between 1993 and 2007 with 840 contemporary racing controls, stratifying animals into 26 birth-year cohorts to identify whether particular ancestors appeared disproportionately in affected versus unaffected populations. Twenty-six ancestral lines demonstrated statistically significant contributions to disease status, with eleven stallions and broodmares contributing significantly more to affected cohorts and fifteen contributing preferentially to controls (P ≤ 0.05); critically, one stallion and one broodmare showed very highly significant associations with affected horses (P ≤ 0.001), suggesting concentrated genetic risk within specific pedigree lines. These findings indicate that atrial fibrillation in Standardbreds exhibits familial clustering around particular sire families rather than polygenic inheritance, which has important implications for breeding decisions and warrants further investigation into the functional genetic variants segregating within high-risk lineages. For practitioners involved in breeding programme management, this research supports selective exclusion of high-risk ancestors and their descendants from breeding programmes, whilst identifying which pedigree lines warrant closer cardiovascular monitoring in young racehorses destined for competition.
Read the full abstract on PubMed
Practical Takeaways
- •Breeders of Standardbreds should be aware that certain sire lines carry significantly elevated risk for atrial fibrillation and should consider genetic screening and pedigree analysis in breeding decisions
- •Veterinarians managing Standardbred racehorses should counsel owners on familial risk factors; horses from high-risk pedigrees warrant proactive cardiac monitoring
- •While heritability is modest, the identification of specific ancestral contributors suggests that selective breeding away from affected lineages could reduce AF incidence in the population over time
Key Findings
- •Atrial fibrillation in Standardbred racehorses shows modest heritability (h² ≈ 0.15) with significant ancestral genetic contributions
- •26 ancestors had statistically significant marginal contributions to AF phenotype, with 11 contributing more to affected cohorts and 15 to controls (P ≤ 0.05)
- •One stallion and one broodmare showed very highly significant contributions to affected cohorts (P ≤ 0.001), indicating familial clustering of AF risk
- •The arrhythmia demonstrates particular prevalence in descendants of one specific sire family, suggesting identifiable genetic predisposition