Without a Tail to Sit On

Dr. Cattanach claims puppies like this don't exist. It's a homozygous NBT bobtail corgi without a tail, no anal opening, structural defects, and an opening to the spine. Defective puppies like this are the direct result of breeding bobtail x bobtail and are sometimes carried to term and born alive.

I am somewhat amazed at the positive responses to this [Toller x Aussie] cross. I have had 20 years of vitriol against my Corgi x Boxer cross for every reason imaginable, but I kept it going as I felt that to give up – and so failing – I would damage the leverage it gave to the concept of breed crossing for health reasons. So the seemingly easy acceptance of the Toller cross is perplexing even if done for a different reason.

– Dr. Cattanach

Those of us in the dog world who support the free and open application of outcross breedings within a registry system have previously looked to the work of Dr. Bruce Cattanach’s natural bobtail boxer program with interest.  Along with the LUA Dalmatian project, it served as a go-to example of a practical out cross with good documentation that could quell the fears of the Pure-Blood-Brigade™ regarding instant and permanent breed ruination should someone anywhere breed two dogs that weren’t pedigreed in the same breed.  It still stands as an excellent example of how quickly you can restore breed type even with an extreme outcross.

But as the movement matures I think it’s advisable to retire Dr. Cattanach as a spokesman for the moral implications and justifications for outcross breeding. It must be noted that despite claiming that he persevered criticism of his program to one day help others who would outcross for health reasons, his Steynmere Boxer x Corgi program is exactly the opposite of this ideal.  He purposely inserted a gene which causes dysfunction into a breed which did not have this gene and he did so for the explicit purpose of evading a ban on manual tail docking.  This is a net-increase in disease, infertility, and disorder in the breed and I don’t think this action squares ethically.

No tail, no rectal opening, open hernia leading to spinal canal.

Compare a surgical procedure with very few complications or side effects that can be carried out with skill and efficiency and which leaves no permanent genetic mark on the breed vs. a semi-lethal gene which is implicated in a plethora of complications and negative side effects which can’t so easily be removed and which is far from precise in presentation.  The gene doesn’t even solve the issue 25-33% of the time and it will never breed true.  If tail docking is thought to be overly cruel simply for the momentary pain it causes, how can the basket of crap that comes along with the bobtail gene be considered more humane?

The greater theme of the outcross for health movement is to combat and repair the damage done by questionable breeding practices done in the name of conformation.  Isn’t inflicting the bobtail disfigurement gene on a breed so that they can still be made to fit a conformation ideal (and for no other reasonable purpose) the exact sort of breeding scheme the outcross movement is against? The Cattanach boxer-corgi cross was not done for health, it was done to promote disease.  It was not done to add or preserve diversity, it was actually done to preserve a conformation ethic and subvert an animal cruelty law.  This is not an outcross done for noble reasons, it was done to replace surgical scissors with a genetic hammer for the shallowest of reasons: historical aesthetics. New research and understanding of the T-box mutation also casts doubt on Cattanach’s assertion that there’s “nothing to worry about” with a single copy of the bobtail gene, that all homozygotes are harmlessly lost before birth, and that litter sizes are not affected.


Whatever the correct interpretation of the discordant evidence, the molecular data establish that the homozygous Corgi bob-tail is a lethal condition. The term, lethal, has an ominous ring to it. It suggests something totally undesirable. Yet, having pondered the issue at length I have to conclude that while the evidence of lethality is disappointing, it is not an ethical problem. Without any detectable ill-effects, the only undesirable feature of the bob-tail condition is that it will not breed true. There will always be a 25% expectation of long tailed pups appearing. That we now know why this occurs simply means that, in a sense, we now know too much.

So! If there are no ill effects, if litter sizes are not reduced, if the only unwanted feature is the persistent appearance of some long tailed pups in litters, is this acceptable in the event of a docking ban? I suggest that it is now up to individuals to decide on this, and as I am now content that there is nothing nasty about the gene, I see no ethical reason for continuing to keep total control over these bob-tail Boxers. The situation is no different from that for all other breeds having this bob-tailed gene.

– Dr. Cattanach

The arguments Cattanach makes for bobtail don’t hold true in the light of more evidence: Litter sizes are reduced, there’s actually up to a 33% expectation of long tailed pups making this scheme considerably less effective, and ill effects from a single bobtail gene can not be ruled out in good faith.

For the Swedish Vallhunds [who have the same mutation as Corgis and Bobtil Boxers], analysis of the litter sizes from short-tailed x short-tailed crosses revealed a 29% reduction in litter size, further supporting recessive embryonic lethality of the mutation.

Hytonen, et al. Ancestral T-Box Mutation Is Present in Many, but Not All, Short-Tailed Dog Breeds, Journal of Heredity 2009.

Another survey study of bobtail Australian Shepherds which share the same gene also documented a reduction in litter size in NBT x NBT matings:

Avg. # pups in NBT X NBT litters = 5.83
Avg. # pups in Full-tail X NBT litters = 7.55
Avg. # pups in Full-tail X Full-tail litters = 7.22

This documented reduction in litter size is consistent with homozygous NBT puppies being killed and not being harmlessly replaced as Cattanch suggested: “The hypothesis for the bob-tails is therefore simply that homozygous bob-tail loss replaces natural loss. Their loss in effect enhances the chances of other embryos surviving.”  There is no documented evidence that loading up a uterus with fetuses that will mostly die at some point before birth is in any way beneficial to the dam or the other puppies.  Frankly, this idea is ridiculous and opens the door to lesser minds and breeders with questionable ethics using Dr. Cattanach’s words to justify doubling up on any sort of lethal genes for aesthetic purposes while claiming that they’re helping the surviving puppies and that small litter sizes are good.

Cattanach also downplays the failure rate of NBT to achieve bobtail dogs:  “There will always be a 25% expectation of long tailed pups appearing.”  This is only correct if every homozygous NBT is born and thrives, but we know this isn’t the case.  If all homozygous pups are nonviable, then we have a resulting ration of 2/3 bobtail and 1/3 normal tail because the original homozygous NBT population doesn’t appear and thus can’t be counted.  A breeder who doesn’t realize this change in expected ratios would expect only 1 in 4 puppies to be long tailed, but nature will actually produce up to 1 in 3 undesirable long tails.  This is not an insignificant difference and makes the NBT gene solution a less attractive option.

The Australian Shepherd study confirms the ~33% failure rate:

% Full-tailed pups in this study = 66.25%
% NBT pups in this study = 33.75%

Cattanach is aware of the Norwegian study which shows the same effect:

Norwegian Corgi data indicated a shortage of bob-tail pups (66%) relative to the 75% expected from bob-tail x bob-tail matings, suggesting that the homozygotes are lost before birth.

This clearly means a failure rate of 34% versus 25%.

The final claim Dr. Cattanach makes is that a single copy of the bobtail gene is “Without any detectable ill-effects.”  While no study to my knowledge has intended to look specifically at lumbar disease within breeds comparing no copies to one copy of the bobtail gene, there is too much lumbar disease in T-box breeds to rule this out in good faith without further investigation.

The Australian Shepherd study documented that NBT puppies were 7 times more likely to have kinked tails than normal puppies (5.76% versus 0.8%), and that 1.6% of the NBT puppies were born with imperforate anuses and all three died before 8 weeks.  No non-NBT puppies had imperforate anuses.  Of the 6 NBT x NBT litters in the study, one litter of 5 puppies was born premature and nonviable.  No other litters were premature.

The survival rate of NBT x NBT litters was also lower (the study did not publish individual dog data):

8 week survival rate NBT x NBT: 77.14%
8 week survival rate NBT x full:  97.99%
8 week survival rate full x full: 94.58%

Pembroke Welsh Corgis, the breed Cattanach turned to for his outcross are noted for their “High” risk profile for Intervertebral Disc Disease, which is consistent with the malformations of the spine that have been documented both in dogs and in the many other species which have a T-box mutation.

A discussion this week on a Swedish Vallhund group also suggests that the bobtail gene causes problems in housebreaking single copy NBT puppies:

Barahwolfe Kennel
Rose Madsen believed that sometimes the bobtailed or no-tailed examples of the breed could be hardest to toilet train taking longer than the dogs with tails.

November 12 at 12:29am

Lucy Smith They [bobtails] toilet differently too.

November 12 at 12:31am

A survey of the other breeds with the same T-box mutation shows a consistent pattern: even a single copy of the bobtail mutation might have adverse health effects in regards to musculature, bone structure, and vasculature of the lumbar region.  Possibly related conditions include: degenerative myelopathy (disease of the spinal nerves leading to muscle weakness and lack of coordination and paralysis), cervical spondylosis,  narrow intervertebral space, vertebral osteophytes, hemivertebrae, incontinence and delays in housebreaking, Legg–Calvé–Perthes syndrome (necrosis of the hip joint due to underdevelopment in the lumbar region, also consistent with the abdominal wasting seen with T-box mutations.), etc.

The last assertion Dr. Cattanach makes is that the homozygous NBT puppy is never born and absorbed harmlessly very early in the pregnancy.  Not only is there zero evidence (due to a lack of scientific inquiry) of when homozygous puppies become nonviable and die nor their direct effects on the health of the dam and womb mates, there have been documented homozygous bobtail puppies now that there is a DNA test and a few rigorous inquiries looking for them.

A homozygous NBT puppy born alive but without a tail or an anal opening.

Here is an x-ray of a Pembroke Welsh Corgi puppy (distinct from the one pictured above) that was tested homozygous for bobtail and was born alive.  The puppy presented without a tail and atresia ani.  You can see air in its lungs and the build up of gas in the intestines.  A stillborn normal tailed puppy from the same litter was x-rayed above and to the right of the double NBT puppy for comparison and you can see not only how much smaller the NBT puppy is but also the deformity of the spine and the significant rear wasting in muscle mass.  The puppy was euthanized.

Unlike our state of uninformed ignorance when Dr. Cattanach first made his proclamation of a harmless NBT gene and worry-free NBTxNBT breeding, time and more rigorous examination (including a DNA test for NBT which was developed with assistance from Dr. Cattanach) has begun to document that Dr. Cattanach’s bases for concluding that there was no ethical considerations no longer hold true and never did.  Homozygous NBT puppies ARE born alive and they are a mess.  Litter sizes are smaller and not in an insignificant way.  NBT as a substitute for tail docking is largely ineffective with up to a third of puppies having long tails and some percent more of heterozygous NBTs having shorter but not stubby tails.  And even a single copy of NBT is not cleared as harmless, certainly not less than a manual tail docking procedure.

Given that Dr. Cattanch’s assertions are now documented false, his conclusion is invalidated and the ethics of breeding NBT to NBT is not so cut and dry.  Should Dr. Cattanch choose not to revise his position, invoking his name in the movement to open stud books and demystify the routine practice of outcrossing is a poor strategy and unjustly opens the movement to criticism that should be reserved for those who stubbornly seek to avoid outcrossing–namely that the opponent’s advocated breeding scheme increases disease and disorder within the breed for little to no apparent gain solely to attempt to conform to an historical aesthetic.

This is the sort of breeding scheme we should seek to avoid, not one we should hold up as an example.

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About Christopher

Christopher Landauer is a fifth generation Colorado native and second generation Border Collie enthusiast. Border Collies have been the Landauer family dogs since the 1960s and Christopher got his first one as a toddler. He began his own modest breeding program with the purchase of Dublin and Celeste in 2006 and currently shares his home with their children Mercury and Gemma as well. His interest in genetics began in AP Chemistry and AP Biology and was honed at Stanford University.