Work was performed at Vetsuisse-Faculty, University of Berne, Switzerland. Previous presentation of data briefly (1 PowerPoint slide) mentioned in a lecture at the ACVIM conference 2008 in San Antonio.
Mixed Inheritance of Equine Recurrent Airway Obstruction
Article first published online: 25 MAR 2009
Copyright © 2009 by the American College of Veterinary Internal Medicine
Journal of Veterinary Internal Medicine
Volume 23, Issue 3, pages 626–630, May/June 2009
How to Cite
Gerber, V., Baleri, D., Klukowska-Rötzler, J., Swinburne, J.E. and Dolf, G. (2009), Mixed Inheritance of Equine Recurrent Airway Obstruction. Journal of Veterinary Internal Medicine, 23: 626–630. doi: 10.1111/j.1939-1676.2009.0292.x
- Issue published online: 19 MAY 2009
- Article first published online: 25 MAR 2009
- Submitted October 22, 2008; Revised December 10, 2008; Accepted January 12, 2009.
- Major gene;
- Segregation analysis
Background: Mode of inheritance of equine recurrent airway obstruction (RAO) is unknown.
Hypothesis: Major genes are responsible for RAO.
Animals: Direct offspring of 2 RAO-affected Warmblood stallions (n = 197; n = 163) and a representative sample of Swiss Warmbloods (n = 401).
Methods: One environmental and 4 genetic models (general, mixed inheritance, major gene, and polygene) were tested for Horse Owner Assessed Respiratory Signs Index (1–4, unaffected to severely affected) by segregation analyses of the 2 half-sib sire families, both combined and separately, using prevalences estimated in a representative sample.
Results: In all data sets the mixed inheritance model was most likely to explain the pattern of inheritance. In all 3 datasets the mixed inheritance model did not differ significantly from the general model (P= .62, P= 1.00, and P= .27) but was always better than the major gene model (P < .01) and the polygene model (P < .01). The frequency of the deleterious allele differed considerably between the 2 sire families (P= .23 and P= .06). In both sire families the displacement was large (t= 17.52 and t= 12.24) and the heritability extremely large (h2= 1).
Conclusions and Clinical Relevance: Segregation analyses clearly reveal the presence of a major gene playing a role in RAO. In 1 family, the mode of inheritance was autosomal dominant, whereas in the other family it was autosomal recessive. Although the expression of RAO is influenced by exposure to hay, these findings suggest a strong, complex genetic background for RAO.