Linebreeding is a gathering of lines in
several generations, back to one or more good dogs and/or bitches.
If we study this 6-generation pedigree of Mallorn's
Coconut, we'll see several names reappear several times, like Boothgates
Headliner, Charway Ballywill, Brandhams Hot Choice for Oulsmi, etc. In
a 10-generation pedigree we would see this even more.
This pedigree is a typical example of linebreeding.
Both the pedigree of the sire and the dam go back to outstanding, very
well known Labradors.
The main purpose of linebreeding is to transmit
a large percentage of one outstanding ancestor's genes from generation
to generation without causing an increase in the frequency of undesirable
traits often associated with inbreeding.
Because linebreeding is not based strictly
on mating closely related individuals (with very similar gene types), it
does not necessarily cause a rapid increase in homozygous gene pairs. Consequently,
it will not expose undesirable recessive genes as extensively as closebreeding.
For this reason, linebreeding is generally a safer inbreeding program for
most breeders. Every good strain is linebred, usually to the strain itself,
because top breeders know heir stock from tip to toe, so know exactly how
to use their own bloodlines.
Loose linebreeding over successive
generations will result in more variations of physical appearance than
inbreeding or close linebreeding, but it will keep the physical
structure of size and shape with fewer long term risks.
The mathematics of close
Call our star bitch “A”. Remembering
that each puppy is ½ of each parent, her half-sibling offspring
would all be 50% A, and 50% of the unrelated sires; we’ll call them B and
C. So we can describe the offspring as ½A½B and ½A½C.
If you breed these two half siblings, the
puppies each get ½ of their genes from each of their parents, and
doing the algebra, we see that the puppies from that linebred cross are
½ of (½A½B) plus ½ of (½A½C),
coming to ¼A¼B¼A¼C. Adding up the fractions,
you will see that the puppies are only ¼ each of the less desirable
sires B and C, but are still at ½ of our very desirable bitch A.
And when you breed those puppies to another “A” line out of unrelated sire
D, they come up to be ½A,1/8B,1/8C,¼D; and they will
still be at 50% of A.
By starting with half-siblings, out of otherwise
unrelated lines, we can breed forward endlessly, and still stay at 50%
of our desirable bitch A. This is actually easier if the outstanding individual
is a dog, as you can create many half-siblings within the same generation,
but as you can see from our bitch "A" example, it is still possible to
line breed with a bitch, just slower to get started.
The key to working with a bitch would be
to breed her to a different dog every time, and to hang on to the half
siblings. You will then be able to start linebreeding, all at that magical
50% of “A”. Note that if we breed back a generation, for instance dog AB
back to bitch A, we have then crossed over into inbreeding, resulting in
an animal that is 75% A and 25% B. Anytime the percentage of any
one animal goes over 50%, you are inbreeding; by definition, line breeding
will never take you higher than 50%.
Inbreeding is mating the dog to one of its
immediate ancestors without introducing any fresh blood at all. Although
it is extremely useful in telling the breeder what faults may be hidden
in his strain, and also fixes the virtues, which may outweigh the faults,
inbreeding should only be used by extremely experienced breeders who know
their dogs in and out for a longer period of time, and then only if absolutely
necessary for an essential fact.
When dogs are inbred haphazardly, without
culling of inferior stock, many undesirable traits may become predominant
in their offspring. For example, the inbred dog's ability to resist disease
and his overall performance capacity are often depressed. The growth rate
of the inbred puppy, and the average mature size within the inbred litter,
frequently decreases. Nonselective inbreeding is directly related to a
depressed fertility rate, an increase in abortion and stillbirth. Some
basic principles of genetics show why these traits are directly related
Closebreeding, a breeding system
which uses extreme inbreeding, such as mating between siblings or between
parents and offspring, is also sometimes used by experienced breeders,
but again has its risks and should only be resorted to for a very good
Inbreeding and closebreeding are riskfull
breeding systems, and in a time when culling your litters was common
practice it was easier to get rid of the undesired results. Nowadays you
will be dealing with your vet in any event when it comes to euthanasing
any pup. Some vets are
not prepared to euthanase in all instances;
for example, if they are of the opinion that too much white is not a satisfactory
reason they might very well decline your request. And unfortunately there
are commercial breeders who will refuse to cull their litters at all, because
every puppy, even a bad one, is a source of income.
Example of outcrossing. In this 6-generation
pedigree you will not find the name of one ancestor twice. I don't know
the dog in question, so I don't know what the outcome is.
When outcrossing you introduce a dog that
contains none of your own strain whatsoever and none or very few of the
names appearing in your bitch's 4-generation pedigree. You would only outcross
if you're not satisfied with your own strain at all. Crossbreeding initiates
the desired change, while inbreeding or linebreeding increases the ability
of each generation to breed "true to type".
The chances of getting something good out
of an outcross breeding are remote. However, if the breeder is planning
ahead, this may merely be a step in a longer term strategy. For outcrossing
to work, the next logical step is to breed close again to the line.
When you outcross you basically leave it
up to great randomness about what the puppies will look like. You will
NOT get the best charactertics of the mother and the father. In all likelihood,
you will get a very average looking litter or worse.
- A Practical Approach