The effect of inbreeding, body size and morphology on health in dog breeds

Post is based on Canine Medicine and Genetics’ post, published 02 December 2021


Dog breeds are known for their distinctive body shape, size, coat color, head type and behaviors, features that are relatively similar across members of a breed. Unfortunately, dog breeds are also characterized by distinct predispositions to disease. We explored the relationships between inbreeding, morphology and health using genotype based inbreeding estimates, body weight and insurance data for morbidity.

“The inbreeding values within dog breeds were very high, with the mean being 0.24, just below the coefficient of inbreeding obtained from breeding full siblings. The breeds with low inbreeding included recent cross breeds (Tamaskan Dog, Barbet and Australian Labradoodle) and landrace breeds (Danish-Swedish Farmdog, Mudi and Koolie), supporting the notion that high inbreeding is a result of closed stud books or small numbers of founders or both. It also demonstrates that it is possible to have consistent breed type without inbreeding.”

– From the publication “The effect of inbreeding, body size and morphology on health in dog breeds”


The average inbreeding based on genotype across 227 breeds was Fadj = 0.249 (95% CI 0.235–0.263). There were significant differences in morbidity between breeds with low and high inbreeding (H = 16.49, P = 0.0004). There was also a significant difference in morbidity between brachycephalic breeds and non-brachycephalic breeds (P = 0.0048) and between functionally distinct groups of breeds (H = 14.95 P < 0.0001). Morbidity was modeled using robust regression analysis and both body weight (P < 0.0001) and inbreeding (P = 0.013) were significant (r2 = 0.77). Smaller less inbred breeds were healthier than larger more inbred breeds.


In this study, body size and inbreeding along with deleterious morphologies contributed to increases in necessary health care in dogs.

To read the full post, click here.

Long Bay Labradoodles shares for each breeding dog COI% in dog details. For planned litters COI is shared with the puppy buyers. We target with COI% in our breeding program max 2,5. Our COI% is calculated with 10 generations if available.

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