HEALTH
Natural bobtail and NBT
Tested variant, tail length and limitations of the evidence.
30 SECONDS · In a nutshell
A natural bobtail may be associated with the NBT variant of the T gene. The result only describes the tested variant.
VARIABLE LENGTH
Tail appearance does not establish genotype
3 MINUTES → EXPERT · Explanation and sources; open the sections to explore further
Natural tail and genetics
Natural bobtail: the NBT variant and tail length
Australian Shepherds may be born with a full tail or a natural bobtail of variable length. This trait can be associated with the C189G variant of the T gene, known as NBT.
Natural from birth
A naturally short tail is not an amputated tail. Appearance alone does not replace documentation or a genetic test.
Variable length
The variant is associated with a shortened tail of variable length; the test does not predict an exact length. A negative result excludes the tested variant, not every possible cause of a short tail.
What the evidence says
According to UC Davis, two copies of the NBT variant are usually associated with embryonic loss. Indrebø et al. (2008) described two Pembroke Welsh Corgis that reached birth with severe malformations incompatible with life. These observations concern Corgis, not Aussies.
Tail appearance does not establish a genetic result. If you receive a test report, check which variant was analysed and which dog it concerns.
From the guide to your Lunamar records
The library explains breed and health concepts. The private platform organises dogs and kennels, preserves evidence, explores pedigrees and records reproduction. Reading a guide does not create records, grant access or confirm a result.
In Health and genetics, preserve the dog’s report and review variant, copies, inheritance and page before marking it Documented. A genetic finding, clinical suspicion and diagnosis are different facts. Recording a result does not prescribe treatment or automatically approve a mating.
For an individual dog, discuss tests and family history with the veterinarian. The system does not diagnose or decide treatment, ovulation or insemination timing. Missing data must remain identified as pending information.
Open the private platform user guides
Application to Lunamar features reviewed on 22 October 2026. Each reading retains the scope of its clinical sources and review dates.