High heritabilities for BOAS grades in Finland

Brachycephalic obstructive airway syndrome (BOAS), observed in many flat-faced dog breeds, is one of the most urgent welfare problems in pedigree dogs.

A Finnish study evaluated the results gained from the Finnish Kennel Club's (FKC) BOAS test and estimated the heritability for clinically graded BOAS signs. The BOAS test used by the FKC includes:

• an exercise component with a recovery assessment,
• BOAS grading by a veterinarian that evaluates upper respiratory signs before and after exercise, and
• a nostril stenosis assessment.

The analysed test results were from the years 2017–2022.

Results and conclusions:

• The majority (80%) of dogs (n = 957) participating in FKC BOAS testing were English Bulldogs, French Bulldogs, and Pugs. In 2022, 89–100% of the litters from these three breeds registered with the FKC had at least one parent tested for BOAS.
• The proportion of dogs failing the exercise test was highest in English Bulldogs (11%), followed by French Bulldogs (4%), and Pugs (3%).
• In these three breeds, moderate to severe BOAS signs were reported in 28%, 22%, and 30% of dogs, respectively. The proportion of moderate to severe nostril stenosis was highest (71%) in Pugs, followed by French Bulldogs (55%), and English Bulldogs (40%).
• Estimates of heritability for BOAS grade were separately calculated for these three breeds and for all dogs, and the estimates were moderate to high, ranging from 0.39 to 0.58.
• The exercise test alone did not sufficiently identify dogs with moderate to severe BOAS signs.
• To better consider the complex nature of BOAS and breed differences, exercise tolerance, the severity of upper respiratory signs (BOAS grade) and nostril stenosis should all be assessed together in breeding animals.
• The heritability estimates for veterinary-assessed BOAS grade indicated that BOAS grade could be used in selective breeding to obtain less-affected offspring.

The study is open access and can be read in the link below:

Lilja-Maula, L.I.O., Mäki, K.H., Aromaa, M.K. et al. Evaluation of brachycephalic obstructive airway syndrome breeding test results in Finland from 2017 to 2022. Acta Vet Scand 66, 35 (2024). https://doi.org/10.1186/s13028-024-00755-9