Mixed inheritance of equine recurrent airway obstruction.
Authors: Gerber V, Baleri D, Klukowska-Rötzler J, Swinburne J E, Dolf G
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Mixed Inheritance of Equine Recurrent Airway Obstruction Equine recurrent airway obstruction (RAO) represents a significant respiratory disease in performance horses, yet its genetic basis remained poorly characterised until this investigation. Gerber and colleagues analysed 761 offspring from two Warmblood sire families and a reference population of 401 Swiss Warmbloods, using segregation analysis to test five inheritance models (environmental, general, mixed, major gene, and polygenic) against respiratory clinical scores. A mixed inheritance model—incorporating both a major gene and polygenic effects—best explained RAO transmission in all datasets, significantly outperforming purely monogenic or polygenic models, though notably the deleterious allele frequency varied considerably between the two sire families. Critically, one family displayed autosomal dominant inheritance whilst the other showed autosomal recessive patterns, with both families exhibiting extraordinarily high heritability estimates (h² = 1) and substantial displacement values, indicating a powerful genetic component underlying disease expression. These findings have substantial implications for breeding programmes: they suggest RAO cannot be simply controlled through single-gene selection strategies, requiring instead multi-criteria approaches that account for complex genetic architecture, whilst the marked differences in inheritance patterns between families emphasise the importance of pedigree analysis and family-specific risk assessment in breeding decisions and client education regarding RAO predisposition.
Read the full abstract on PubMed
Practical Takeaways
- •RAO has a strong genetic component with complex inheritance patterns that vary between families; breeders should exercise caution when selecting breeding stock from RAO-affected lines
- •Environmental factors alone do not explain RAO susceptibility—genetic screening or pedigree analysis may help identify at-risk individuals regardless of management
- •The different inheritance modes between families suggest RAO may involve multiple genetic pathways; selection strategies need to account for family-specific genetic risk rather than applying one universal approach
Key Findings
- •Mixed inheritance model best explains RAO inheritance pattern across all datasets, significantly better than major gene or polygene models alone (P < 0.01)
- •A major gene plays a clear role in RAO with autosomal dominant inheritance in one family and autosomal recessive in the other
- •Deleterious allele frequency differed considerably between the two sire families, suggesting different genetic architectures despite same phenotype
- •Heritability estimates were extremely large (h² = 1) with substantial displacement values (t = 17.52 and t = 12.24), indicating strong genetic influence independent of environmental factors