Effects of genetic and environmental factors on chronic lower airway disease in horses.
BACKGROUND
Environment and genetics influence the manifestation of recurrent airway obstruction (RAO), but the associations of specific factors with mild, moderate, and severe clinical signs are unknown.


OBJECTIVE
We hypothesized that sire, feed, bedding, time outdoors, sex, and age are associated with clinical manifestations of mild, moderate, and severe lower airway disease.


METHODS
Direct offspring of 2 RAO-affected Warmblood stallions (F1S1, n = 172; F1S2, n = 135); maternal half-siblings of F1S1 (mHSS1, n = 66); and an age-matched, randomly chosen control group (CG, n = 33).


METHODS
A standardized questionnaire was used to assess potential risk factors and to establish a horse owner assessed respiratory signs index (HOARSI 1-4, from healthy to severe) according to clinical signs of lower airway disease.


RESULTS
More F1S1 and F1S2 horses showed moderate to severe clinical signs (HOARSI 3 and HOARSI 4 combined, 29.6 and 27.3%, respectively) compared with CG and mHSS1 horses (9.1 and 6.2%, respectively; contingency table overall test, P < .001). Sire, hay feeding, and age (in decreasing order of strength) were associated with more severe clinical signs (higher HOARSI), more frequent coughing, and nasal discharge.


CONCLUSIONS
There is a genetic predisposition and lesser but also marked effects of hay feeding and age on the manifestation of moderate to severe clinical signs, most markedly on coughing frequency. In contrast, mild clinical signs were not associated with sire or hay feeding in our populations.
Ramseyer
Alessandra
A
Equine Clinic, Vetsuisse-Faculty, University of Berne, Switzerland.
Gaillard
Claude
C
Burger
Dominik
D
Straub
Reto
R
Jost
Ursula
U
Boog
Cornel
C
Marti
Eliane
E
Gerber
Vincent
V
D000818:Animals; D002908:Chronic Disease; D020022:Genetic Predisposition to Disease; D006734:Horse Diseases / Q000209:etiology* / Q000235:genetics*; D006736:Horses; D008297:Male; D012140:Respiratory Tract Diseases / Q000209:etiology / Q000235:genetics / Q000662:veterinary*; D012307:Risk Factors