Presenter Joanna Ilska
Authors Joanna J. Ilska (1), Fern McDonnell (1), Jane F. Ladlow (2, 3)
Affiliations 1. The Kennel Club 2. Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom 3. Granta Veterinary Specialists Referrals, Linton, United Kingdom
Presentation Type Talk
Abstract
Brachycephalic Obstructive Airway Syndrome (BOAS) is among the most serious welfare concerns affecting companion dogs. Owners often underestimate the severity of clinical signs, while the same morphological traits that predispose brachycephalic breeds to BOAS are also those most valued by prospective puppy buyers. As many owners and breeders remain committed to these breeds, and given the limited phenotypic variation in craniofacial morphology within the most extreme populations, there has been continuing debate about whether meaningful within-breed improvement in BOAS is achievable. To date, only limited numbers of phenotyped dogs have been available, constraining accurate estimation of genetic parameters.
We analysed data from 4,301 dogs across three extreme brachycephalic breeds assessed under the Respiratory Function Grading Scheme (RFGS), where clinical grades reflect the severity of BOAS. Genetic parameters were estimated using univariate animal models incorporating full pedigree relationships to partition phenotypic variance into additive genetic and environmental components. Estimated breeding values (EBVs) and their accuracies were subsequently derived for all individuals in pedigree. Population structure was explored within each breed using principal component analysis (PCA) based on pedigree-defined relationships.
In this largest dataset to date, the prevalence of BOAS was estimated at 15–20%, substantially lower than previously reported. Significant additive genetic variance was detected for RFGS grade, with heritability estimates ranging from 0.21 to 0.45 across breeds, indicating that BOAS susceptibility is moderately heritable and therefore amenable to selection. However, EBV accuracies were generally low, reflecting limited uptake of RFGS testing. PCA revealed evidence of population substructure within breeds. Dogs bred outside the official breed standard, here defined as those with non-standard coat colours, were under-represented among tested animals, suggesting sampling bias and uneven distribution of selection opportunities across subpopulations.
These findings demonstrate that genetic progress to improve respiratory health is feasible through within-breed selection, provided participation in health testing is expanded. Greater engagement across all breeding lines will be essential to enhance EBV accuracy and ensure that selection for improved airway function delivers meaningful welfare gains in these popular but high-risk breeds.