Can Vet J. 2026 Aug 1;67(8):882-888. eCollection 2026 Aug.
ABSTRACT
BACKGROUND: Natural bobtail phenotypes, mostly caused by a mutation in the T-box transcription factor T-gene, occur in several dog breeds. Although generally considered benign, reduced tail length may co-occur with structural changes in the lumbosacral spine, raising potential welfare concerns.
OBJECTIVE: The objective of this study was to investigate whether natural bobtail phenotypes (short- and stumptails) are associated with the occurrence of lumbosacral transitional vertebra (LTV) in Brittany dogs and Danish-Swedish Farmdogs.
ANIMALS AND PROCEDURES: This retrospective, cross-sectional study included 1679 dogs [Brittany dogs (n = 744); Danish-Swedish Farmdogs (n = 935)] screened through the Norwegian Kennel Club’s hip dysplasia program. Standardized ventrodorsal pelvic radiographs were evaluated for LTV and tail phenotypes. Associations were assessed using chi-square tests, odds ratios (OR) with 95% confidence intervals (CI), and post-hoc standardized residuals. Tail phenotypes were analyzed as a binary variable (bobtail versus normal) in both breeds and as a 3-category variable (stump, short, normal) in Brittany dogs.
RESULTS: Lumbosacral transitional vertebra prevalence was 47.8% in Brittany dogs and 14.9% in Danish-Swedish Farmdogs, whereas the natural bobtail phenotype (stump + short) occurred in 26.7% of Brittany dogs and 11.0% (short) of Danish-Swedish Farmdogs. In Brittany dogs, bobtailed dogs had significantly increased odds of being LTV-positive compared with dogs having a tail of normal length (OR = 2.04, 95% CI: 1.47 to 2.85; P < 0.001), with the strongest association observed in stump-tailed individuals. In Danish-Swedish Farmdogs, the association was weaker and did not reach statistical significance (OR = 1.66, 95% CI: 0.99 to 2.76; P = 0.05).
CONCLUSIONS AND CLINICAL RELEVANCE: Natural bobtail phenotypes are associated with LTV in Brittany dogs, with stump-tailed dogs showing the strongest association. A similar, non-significant trend was observed in Danish-Swedish Farmdogs.
PMID:42544340 | PMC:PMC13429198
