The explanations given below are the fruit of observations that we did, having spent more than 30 years breeding Bourbonnais with short tails, to keep the gene in the breed.
Then I discovered the very interesting experiment of doctor Bruce Cattanach to move the short tail gene from Corgis to boxers, and had the chance to be able to get his wise advices (to see this experiment Click here). The study to which he participated had identified a gene causing this characteristic, we had to know if this gene was at work in the Bourbonnais.
When the doctor Catherine André (from CNRS) accepted to do this research, many enthusiasts got involved and sent their dogÂ’s ADN sample. The result of this study is given by the report written by Samuel Seguin here (in pdf and only in French, sorry): rapport de stage
At the autumn of 2005, Michel Comte found the opportunity to meet Catherine André, the president of the Société Centrale Canine Gérard Arthus and the professor Bernard Denis, to ask them to officialize a test which would enable us to put the mention “natural short tail” on the pedigrees of the Bourbonnais which have it. The idea is to enable the Bourbonnais born with short tail to be showed everywhere in Europe, despite the ban on tail docking that is spreading in numerous countries. It would also be useful that puppies buyers have a guarantee when a "natural short tail" dog is sold to them, we saw too many people buying a docked tail dog as a natural short tail dog (and being disappointed when they have puppies and find no short tail in the litter). Until we have such a test, the only reference for people who want to breed short tail dogs are my files (I keep track of all short tail lines).
One locus is involved, and can bear only two allels:
Allel T -> short tail
Allel t -> long tail
The allel T is dominant compared to allel t.
We have 3 possible genotypes, but one of those genotypes is lethal (meaning that the puppies having this genotype will never be borned), giving 2 phenotypes. In blue the short tail dogs, in red the long tail dogs, in grey the dogs which won't be borned:
|
Genotype |
Phenotype |
|
t-t |
Long tail |
|
t-T |
Short tail |
|
T-T |
Lethal |
|
|
t |
t |
|
|
t-t |
t-t |
|
|
t-t |
t-t |
Expected litter: 100%
of t-t(long tail)
|
|
t |
|
|
t |
t-t |
t-T |
|
t |
t-t |
t-T |
Expected litter: 50%
of t-t(long tail) and 50% of t-T(short tail)
|
|
|
|
|
t |
t-t |
t-T |
|
|
T-t |
T-T |
Expected litter: 25% of T-T(not born), 50% of t-T(short tail) and 25% of t-t(long tail) -> 66% of short tail and 33% of long tail with a litter reduced by 25%
We didn't see the reduction in litter size that were forseen in the few short tail dog to short tail matings we did. This mystery has to be explained.
In a short tail litter, there are no tail puppies (anury) and short tail puppies (brachyury), but we still don't know why. We will have to do some statistics (number of no tail and of short tail in each litter) if we want to understand.