Breeding Myths By JP Yousha
For most dog breeders,
as well as dog buyers, genetics is both a confusing and intimidating topic.
This short article is intended to clarify some commonly held misconceptions
about genetics and to offer some simplified explanations which (hopefully)
will help the average person understand a few basic concepts of genetics that
are important in breeding and owning purebred dogs. A couple of good references
written for dog fanciers are listed at the end of this article for those seeking
more information and more in-depth explanations.
THE MYTHS:
Myth#1. Purebreds are "weaker"
than mutts.
Mongrels display more genetic
faults and inherited disease traits than any one breed. There are endless
sets of statistics to prove this idea is a myth, but they never seem to convince
anyone. This is probably due to the combination of the following:
a) Sick and crippled mongrels are less likely to be counted as they are less
likely to be among the living, let alone among those dogs taken to vet clinic
for expensive care.
b) No owner (breeder/vet) ever attributed a disease to a mongrel's breeding.
c) The "Ugly Tourist" syndrome: many healthy pets live quietly on,
while one sick Irish Setter or a GSD with hip dysplasia gets more than their
share of the focus. Add to this that the better made pets are actually much
harder to find & buy for the average pet owner, who sadly tends to, despite
all good intentions, to buy from the uninformed if not outright uncaring breeder.
d)
It is romantically enticing to think Nature does a better job of taking care
of Her Children than corrupt man does. The fact that "she" doesn't
look after any of "her individual children" is obvious only to those
who study nature carefully. Sickness, death & dying is just exactly how
nature winnows out the numbers to an acceptable level; cruelty by our standards
is a standard event in nature-as is suffering. Nature's idea of "controlling"
disease is to let the afflicted individuals be born, suffer and die.
Myth#2. Inbreeding is bad; it causes
sick and unstable dogs.
This goes with the idea (also erroneous) that inbreeding
doesn't occur in nature. Man's cultural taboos on inbreeding is largely behind
all these myths. Inbreeding (line breeding) & out crossing are essentially
neutral tools used to effect certain ends. It is certainly true that such
a thing as inbreeding depression occurs when there is a loss of diversity
among (some particular) genes in some individuals sometimes in some species,
but there is also such a phenomena as out breeding depression that occurs
when you "mess with" a 'good' set of genes by introducing "new
blood" into a breeding program. All this is demonstrated in wild as well
as zoo populations as well as various domestic animal breeding programs. The
point is you just cannot point & say "inbreeding is bad, out crossing
is good;" nature is never than simplistic. Bad breeding decisions often
end in sick & unstable animals, but even the best breeding program has
individuals who may fall ill. Along with this is the problem of confusing
heterozygosity with heterosis (hybrid vigor). The latter is a first generation
trait that occurs ONLY in the offspring of two individuals who are themselves
from pure (in)bred strains; heterozygosity is a term that relates to whether
a given individual has two or one kind of gene (alleles) at any given gene
location (locus). The two terms don't even relate to the same level of discussion,
and a hybrid is not necessarily "better." Having information on
the actual animals in question is what is critical & no formula can replace
that all important criteria. The results of any breeding demonstrate the skill
(& luck) of the breeder. One of the most inbred lines of dogs in the world
has the lowest breed incidence of hip dysplasia and the highest success rate
as superior companion dogs--the seeing eye German Shepherd. Which is not to
say "inbreeding is good;" the old breeder's saw about having to
do an outcross every few generations is based on the observation that continuous
inbreeding over generations can result in "inbreeding depression;"
a phenomena, assembly, having to do with having too much similarity (homozygosity)
among certain genes (such as immune genes). The point is one simply does not
make breeding or buying choices based on single criteria or "cookbook"
formulas--random out crossing is as deadly as blindly linebreeding--smart
breeders make careful selections every generation.
Myth#3. If it is a genetic trait &
you have the gene, you are going to get the disease, etc. associated with
the trait.
This is probably one of the most commonly
held & terribly wrong notions people have about genetics. Innate does
not mean fated. Having a gene for some trait may be a LONG way from having
the trait expressed; you won't get sick necessarily just because you have
a gene for a disease. Genes don't "cause" disease; the expression
of them may. Of course "carriers" are best identified & eliminated
when possible from the breeding stock, but such ideal circumstances may not
be available & it's critical to recognize that genetic traits are not
like a scarlet letter that brands someone as a "defect," just as
it's critical to recognize that we all (& all our dogs) carry defective
and even lethal genes. The key, again, is selection: selection as a breeder
for what defects are tolerable (i.e. those cosmetic or fashion) and which
are not (i.e. those deadly or costly).
Myth#4. If the environment affects
the course of a disease/trait, then that proves the trait is not genetic.
This is the twin of myth #3 & just about
as common. Environment is PART of the genetic inheritance of a person or dog:
a certain environment is necessary for each and every gene to get "turned
on" & expressed. They work TOGETHER, not in opposition. For example,
if a dog with genes for hip dysplasia is fed carefully with low protein &
low calcium and kept from any real exercise, this dog may express the genes
later and with less obvious original bone changes than the pup who eats a
ton & runs around unsupervised. Both will end up with arthritis, likely,
& both EQUALLY are going to pass on their genes for this crippling disease
to their offspring. The first dog is just less "honest" about what
sort of genetic parent he really is. Diet & supplements can mask the effects
of disease & even control them--think about adult onset diabetes which
is usually controlled wholly by diet. But disease controlled by environmental
manipulation isn't a cure & the offspring of dogs who need enzyme supplements,
for example, are going to display the same kind of pancreatic insufficiency
their parents did, even if none of these animals are ever properly diagnosed
and their genetic defect isolated or even admitted. As Richard Dawkins says:
"A gene's meaning is context dependent."
Myth#5 Genetic means congenital.
People still confuse congenital and inherited. Inherited
means acquired (genetically) from the parent(s). Congenital means present
at birth. Congenital problems can be inherited. But many inherited diseases
are not obvious until the animal is mature. That is EXACTLY why we still have
problems getting rid of them.
Myth#6 You can buy/breed a dog without
undesirable genes.
This puppy buyers often demand and some breeders even
will promise. Every dog alive likely carries some undesirable traits. In the
breeds where this has been systematically studied, every breed individual
is likely to carry for 3-5 unwanted traits (gene load). The question is less
rather IF you will accept unwanted traits, than WHICH you will decree as most
undesirable & which you (and your dog!) can accept and live with. Crooked
tails or missing teeth sure beat heart disease and hip dysplasia---all are
inherited. Which, if you had a choice, would you choose to carry in your line
or have in your dog? This is rather hard for folks to swallow as they believe
in myths#3-5 & think your genes are you destiny and that anything genetic
is some sort of scarlet letter. We all need to learn a bit more of how biology
really works & discard our erroneous ideas not based on the evidence of
nature.
This page is part of a message written & prepared
by JP Yousha for educational purposes & may be reproduced to further that
end. All copyrights remain with the author.
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