Objective—To assess heritability and mode of inheritance
for hypoadrenocorticism in Bearded Collies.
Animals—635 Bearded Collies.
Procedure—Dogs were classified as affected by
hypoadrenocorticism or unaffected. Phenotypic and
pedigree data were analyzed. Heritability was estimated
by use of Bayesian statistical methods.
Regressive logistic models for complex segregation
analyses were used to characterize mode of inheritance.
Results—Hypoadrenocorticism was diagnosed in
60 (9.4%) dogs. Heritability of hypoadrenocorticism
was estimated to be 0.76 with both sexes
affected with equal probability. Evaluation of the
pedigrees did not support a Mendelian autosomal
dominant mode of inheritance. Evidence from the
complex segregation analysis for a single locus of
large effect on hypoadrenocorticism was not convincing.
Conclusions and Clinical Relevance—Hypoadrenocorticism
in Bearded Collies is highly heritable.
Although a precise genetic mechanism responsible
for inheritance of the disorder remains undetermined,
breeding decisions must include consideration of the
genetic likelihood of passing on this deleterious disorder
to offspring of affected dams and sires. (Am J
Vet Res 2002;63:643–647).