The
Bobtail Trait in Australian Shepherds – Part III:
Objectives
of the Ongoing Study
by
Gemi Sasson-Brickson
Reprinted from the July-August 2005 Aussie Times, with permission.
©2005-08 - Imagineer/Gemini Sasson-Brickson
All Rights reserved. All photographs and narratives from this web site are
copyrighted and can only be reproduced with written permission from the author.
(This is the last of a three part
series on the Bobtail Trait in Australian Shepherds, written in relation to my
Study on the Inheritance of the Natural Bobtail in Australian Shepherds.
This article addresses the ongoing study of the inheritance of the NBT in
Australian Shepherds, its objectives and information relating to study
participation, as well as some preliminary findings of the study.
Previous articles covered international laws and regulations and
information on genetics and health.)
Why is it important to understand how the natural bobtail trait is inherited in our breed and what effect it might have on neonatal health, if any? In the initial article of this series, I discussed the docking bans in various countries. This movement was initiated by the enactment of the European Convention for the Protection of Pet Animals, which went into effect in the early 1990’s. Inarguably, the main premise behind these laws is a tenet that docking violates the moral obligation, and thus the role as guardian, that humans have towards their animals. Paragraph 11b of the German Animal Protection Act basically states that it is forbidden to breed animals or change them through either biological or genetic measures so that their body parts (organs, skeletal structure, etc.) will be altered to a degree that such alteration may inflict pain, suffering or damage. Depending on the evidence available, this could be interpreted in varying ways. To date, the German law has mostly been applied to the breeding of excessively aggressive animals. Already, there have been a few cases of registries placing restrictions on the breeding of two naturally bobtailed parents together, perhaps due to some of the myths that were addressed in the second article of this series regarding health and genetics. Before we allow such restrictions to creep further into various registries, it is imperative to study whether or not these precautionary measures are warranted. That is one of the things this study attempts to do.
In the United States, where docking is routinely performed
on Aussie litters, whether or not a dog is NBT is normally not a factor when
deciding which dogs to continue with. Although a few decades ago probably
more emphasis was placed upon retaining the NBT, today American breeders are
looking at many other things like structure, perceived breed type,
situation-specific working traits, performance potential and health issues such
as juvenile cataracts, epilepsy and hip dysplasia. In Europe now, some breeders are selecting away from the NBT,
whether through individual preference or demands from buyers for a full tail, or
due to restraints in breeding options. Conversely, other European breeders
have opted to try to preserve the NBT whenever possible as the identifying
characteristic within the breed that it is. After all, a natural bobtail is
actually a beneficial feature for a dog gathering livestock out of the brush in
that there is no extra hair there to mat or collect burs.
With a considerable percentage of the breed possessing the NBT trait,
either breeding toward or away from NBT’s has the possibility of having a
definite impact on which individuals are retained within the gene pool and
consequently the other traits that they will pass on to their offspring.
This selective pressure poses the potential for what’s called
‘genetic drift’. Maintaining
genetic diversity does provide for more variability in any species – and this
can be both a good or bad thing. Selectiveness
gives us uniformity. Variety gives
up options. Both have their price.
The more selective a breeder is about pulling in or weeding out a certain
trait, the more alike the products of their breeding will be.
But doing so will also further concentrate other traits, good and bad, as
it is not within anyone’s power to sort out genes from each other as if one
were mixing ingredients in a recipe. As
someone who purchased their first Aussie nearly twenty years ago, I have seen
the predominant concerns about the breed shift and alter through the years.
While certain concerns such as poor temperament or debilitating health
defects certainly merit the utmost regard, breeders must always keep in mind the
complexity of genetics and just how many possible gene combinations we are
dealing with when we cross two individuals and get ten puppies.
I mention this because of those European breeders who have reported that
many of their requests are for full-tailed puppies.
I find this a sad situation because there are and have been so many
bobtailed Aussies who have contributed positively to our breed.
Do I think therefore that we should start concentrating on getting more
NBTs so we don’t lose that trait? Certainly
not. What I am saying is that we
should look at the complete picture, full-tail, half-tail or no tail, when
choosing future breeding prospects.
So what does it matter if NBT X
NBT breedings are not allowed in certain countries? Or
even if breeders just choose not to do them?
What happens is that a breeder’s options are reduced.
If the bobtail trait in Aussies is indeed a dominant one, as it is in
Pembroke Welsh Corgis, that means that a fairly large number of our dogs are
genetically NBTs. If one can’t or
chooses not to cross two NBTs, what might have been the best overall choice in
stud dogs for a certain bitch is thrown out as a possibility. The breeder
then must find a stud less suitable that has a full tail. A gradual
drifting away from NBTs in the breed population begins to occur in certain
countries and eventually the number of representatives of unique bloodlines
where the NBT is prevalent become fewer and fewer. Theoretically, this
could lead to the possibility that the gene pool will be skewed towards those
individuals that do not possess the NBT trait, meaning less genetic diversity.
Whenever possible, we should
endeavor to understand the mode of inheritance of any specific trait within a
breed, especially when it is being legislated or ruled upon, and to look at all
aspects of genetic concerns within a breed to so that registries and breeders
will know the importance to be placed upon various traits.
Numerous factors must be weighed when considering a breeding: structure,
ability, temperament, and a variety of notable health concerns that exist in our
breed (including but not limited to: epilepsy, hip dysplasia, autoimmune
disorders and inherited eye diseases such as PRA, CEA and juvenile cataracts).
So, how do we figure out what
health concerns there might be to breeding dogs with bobtails – specifically
the Australian Shepherd? First, we
need to look for clues as to its mode of inheritance. Secondly, we need to
maintain records of what occurs in our litters, compile these results and
analyze them, just as the Pembroke Welsh Corgi breeders did in Norway and just
as Dr. Cattanach did with his bobtail Boxers in the U.K.
During the course of this study
I have run across a fair amount of assumptions and incomplete information. Sometimes, when information is lacking we can only take an
educated guess at things. When
presented with the unknown, there is a natural tendency to assume the worst
possible outcome and to tend to play it safe.
However, when there is information out there and we fail to
incorporate it into the overall picture, we may in the long run do a disservice
to the animals over which we are maintaining the breeding control of.
Therefore, in this one small aspect, that of the natural bobtail in
Australian Shepherds, it is just one more way available to educate ourselves
fully and base our decisions on a sounder pool of knowledge.
Alright folks – here is my
disclaimer. With a background in
laboratory science, I fully understand the importance of conducting a thorough
scientific study; however, lining up beakers in a laboratory or breeding mice
specifically for testing purposes is a far cry from breeding dogs. Of all domestic animals, dogs are perhaps the most broadly
accepted as family members and the breeding of them carries a very heavy
responsibility. So breeding for the
sole purpose of studying their health and genetics is simply not feasible.
If it were possible to survey every Aussie litter born in a given time
period, we could very quickly arrive at some answers.
This would take the cooperation of a national registry and will only
happen if the breeders in any given country feel it is a worthwhile endeavor. Meanwhile, if it’s not possible to study the entire
population over a given period, the most scientific way to conduct a study is to
survey a very broad cross-section of the population.
However, since studying large numbers is usually not possible due to the
man-hours needed, random sampling is often used – for example, like when a survey company, having picked names
at random, calls you (usually at dinner time) during a presidential election
year. Properly defined, a random
sample is one without bias – randomly conducted so that the results of the
sampling reflect the true status of the population.
Random sampling still takes a considerable amount of manpower and
resources, so in lieu of that method, another available course is to survey a
population. A survey basically
means putting the word out that you need input and then waiting for people to
come to you with answers. Surveying
is a means of conducting a ‘voluntary sampling’ of the population – people
volunteer their answers to your questions.
In reality, however, any voluntary sampling is limited by the
number of people who choose to participate and the portion of the population
that their numbers represent, thus introducing bias into the sampling. For
example, it’s entirely possible that the litters represented in this study
will represent a disproportionate amount of crosses with bobtail puppies (I
don’t doubt that’s because the study has the word ‘Bobtail’ in the
title). If ‘X’ per cent of the
litters in this study contain bobtail parents or puppies, it would be improper
to state that ‘X’ per cent of the Aussie population are genetically
bobtailed dogs. If a TV station
conducts a phone-in survey asking, “Do you think the economy is worse than it
was four years ago?”, you are far more likely to get people phoning in who are
dissatisfied with their current financial situation than to hear from a true
general cross-section of the population. Thus,
voluntary surveys are flawed by their own limitations.
In regards to this study, that is both good and bad. The numbers may not represent the whole Aussie population,
but what they do is study some issues more closely related to the presence of
the bobtail, if indeed more bobtail individuals are represented by the study.
I have encouraged, as much as possible, for breeders to submit litters
with all full tails to serve as a control group.
This study only uncovers the tip of the iceberg.
It gives us clues and possibilities.
It writes nothing in stone.
Another possible flaw in this
study is that the tail status of the parents relies on the recordings of the
original breeder of the parents of the litters being studied.
If the original breeder of a parent dog was not diligent in recording
whether the tail of that parent in question was a bobtail or not before docking,
that factor could complicate the data results.
One way to overcome this and begin with completely reliable data would be
to raise a breeding colony of Aussies with different tail lengths and then, over
several generations, study the results. That
would take years and endless resources and I’m not aware of anyone willing or
able to do that for this cause or any other.
Another way is, as mentioned in the previous article of this series, to
find corollary studies in other breeds and follow those leads.
When
I first began this study, I hadn’t found the information on the Pembrokes in
Norway or Dr. Cattanach’s full series of articles on the bobtailed Boxers.
I’m glad I eventually did, but at the start I figured there were a few
basic things we needed to know: inheritance, neonatal health, litter size, tail
status of parents and tail status of offspring.
Inheritance can be deduced from either studying a large sample or several
generations, and by looking for clues in other breeds.
Submitting samples for a DNA test to determine if the gene for the NBT in
Aussies is that same as in Pembroke Welsh Corgis is one way of arriving at an
answer more quickly. I am currently
investigating the possibility of doing this and will post information at a later
date if it is indeed doable.
Meanwhile,
I will be collecting Australian Shepherd litter information through this year
(2005) and then publishing the results. The
information I need from breeders takes a relatively short amount of time to fill
out and provide to me. Most of the
data has been sent to me via e-mail, as the data forms are available online or
can be e-mailed as attachments upon request (my e-mail is imgnr@dnaco.net) .
Pictures are helpful to verify tail lengths, plus I may ask to use some
for the final article; however, they are not mandatory.
I request a 5-generation pedigree, some general information on the
parents (such as previous litter
sizes and tail status before docking, if known), and then the litter data (which
includes tail length or category, total number of pups, number of stillborn
pups, and notes on any neonatal health problems, particularly in regards to the
spinal area or hind quarters). That’s
it.
As
of this writing, I have just over 50 litters in the study.
The more data, the more accurate the findings will be, so any and all
breeders are invited to contribute, including litters with all full tails as
well as those with NBT pups in them. Full
tail litters will help serve as a control group for comparison.
The objectives of this study are to determine a possible mode of
inheritance for the natural bobtail trait, to find out whether or not there is
any clear correlation between the presence of the gene and neonatal health
defects, or if the presence of the gene leads to a reduction in litter size or
has no effect on it. Early results
indicate that the gene for the NBT in Aussies may be inherited in the
same manner as it is in Pembroke Welsh Corgis – a dominant gene with modifying
factors that determine actual tail length in the NBTs – as it appears that a
NBT parent will usually produce some NBT pups, no matter who that dog is bred
to. Whether or not it is the same
gene as the Pembrokes could only be proven by DNA testing.
It is unclear whether there is an increase in spinal defects or other
serious health problems, as there simply has not been enough of these problems
reported in this study thus far. It
could be because that although spina bifida and imperforate anus do exist, they
are actually rare in our breed. In
the matter of litter size when the NBT trait is present – a final analysis of
data will give us some indication about this, but thus far litter sizes have
varied in both litters with all full tails and litters with NBTs present.
What will be most interesting to see is what crosses of NBT X NBT will
produce in the way of litter size, but at this point there have not been enough
of such crosses to state anything one way or another.
Although
pedigrees will be requested on all litters to help
determine
the mode of inheritance, no information will be
disclosed
to the public (or to any individuals). Everything is
confidential.
Study results will only contain numerical data.
No
pedigree information or specific sires or dams will be
mentioned.
The
two data sheets needed for participation in this study may be downloaded from
http://www.*****
or received as attachments directly from me at
****.