Genetics
or environment - which is more important?
This is the old question of which is more
important - nature or nurture? Is
it the dog’s breeding (its genetic makeup) or the way it is trained and cared
for? Both are important and no
amount of training will make a top dog if the genes for performance are not
there. On the other hand, good
genes will not be fully expressed under poor training.
Most working dog traits or characters are
strongly inherited - in other words what you see in a dog's performance will be
passed on to the next generation.
The term "heritability" is used to describe this and is on a
scale from 0 - 100%. Weakly
inherited traits like fertility and litter size are below 10% and strongly
inherited ones like casting would be around 30-40%. This is a guess, as geneticists have not done much study on
working dogs, despite their importance.
Research has shown that hip dysplasia averages around 30-40%
heritability.
What
are working traits?
Heading
dog
·
"Eye" or the ability
to out-stare a sheep. Dogs vary
from "strong" eye to "plain" eye but the trait seems to be
strongly inherited.
·
"Heading" or the
dog's ability to cast around sheep.
Some dogs will naturally take a wide cast and others will run straight
at stock. The dog trialist's ideal
is a pear-shaped cast. Again this
seems to be strongly inherited.
·
"Shedding". An ability to separate one sheep from
another at close quarters.
·
Temperament. This is the dog's "nature"
and breeders say this is fairly strong in its inheritance.
·
“Early maturity” refers to the
ability of a pup to start working at a young age. Again breeders believe this trait is strongly
inherited. The fear with
late-maturing pups is that they may not start to work at all.
·
Not biting or grabbing sheep is
important. Seen in some strains so
must have a fairly strong genetic base.
Can be modified by training but is always there.
Huntaway
·
"Heading". All huntaways should be able to head
stock as in heading dogs. They'll
head without showing "eye".
·
"Noise. They must bark naturally and this seems
to be strongly inherited.
·
"Temperament". Very important and generally very good
in huntaways. They are always
anxious to please.
·
"Force". A trait usually seen best in big dogs
that will push among stock with no fear of getting hurt. A fairly strong genetic trait
perfected by proper training.
·
"Backing". Where a dog will jump on the back of
sheep and walk over them. A trait
which varies a bit in strains, so must have some genetic base.
Physical
traits
Breeders are concerned with such genetic
defects as:
·
Undershot jaw or parrot mouth.
·
Overshot jaw.
·
Normal reproductive organs.
·
Sound bone structure - eg no
hip dysplasia common in some strains.
·
Sound feet pads.
·
Normal palate ie. no cleft
palate.
·
Normal leg length - no
drawfism.
·
No problems with the eye
retina.
Single
genes - simple traits
These are simple traits controlled by
single or very few genes.
When we get to the performance traits like speed, intelligence and
working ability we have to deal with thousands of genes. The dog has 39 pairs of chromosomes in
its sex cells (sperm and eggs) and at present we don't know much about the
thousands of genes on them.
These thousands of genes combine when sperm
and eggs are produced into millions of different combinations. So don't expect parents to
produce identical offspring unless you start splitting eggs. In future we could see a lot more
reproductive technology used in dogs and even genetic engineering where we can
separate genes on a chromosome and move them around to engineer more certain
combinations. But before that we
have to do some "gene mapping" to find out what genes are where on
the chromosome. This mapping the
genome of the dog is underway.
Many
genes - complex traits
If you see "variation" in a group
of animals (eg litter mates), then you are dealing with many genes controlling
them, and to improve the next generation, you "select" the best
parents from the present generation.
Sounds simple!
So in dogs you should not be surprised when
some pups in a litter turn out to be good workers and some are not so
good. You will see a whole range
in ability and this variation is then the raw material we use to make
improvement, and the main tool we use is "selection". Variation and selection is what has
made our dogs and what will allow us to improve them. So don't pine for dogs that are like peas in a pod, we need
variation to work on and make progress.
Cloning
Cloning where identical copies of an animal
are made is now possible, and some merit can be seen for it in farm
animals. The idea is good provided
that no problems will occur over time with the animals you produce - because if
they do, then the entire cloned population will get it. You have to make sure that what you are
going to clone is “perfect” in all traits, and that’s asking a lot in the world
of animals. It also restricts
genetic diversity for future selection.
G and E
But remember this "variation: is
caused by two things. First
there's the genes or genetic variation, referred to as "G". Then there's the environment, referred
to as "E" which is the rearing, feeding and training. Some trainers produce better E than
others. You need plenty of G to
make a champion, but you'll not do it without good E. This is the old saying that "90% of the pedigree
goes down the throat."
Mate
the best to the best
This is what the early improvers did long
before the science of genetics was born.
It worked then as it does now.
The only problem is what do we mean by "best"?
Dogs that consistently win at a range of
trials, clearly have the genes needed on the farm. They’re surely the best. But there are some folk who think that today's trials
are too artificial, and don't relate to the commercial farm with large numbers
of stock per person.
The counter argument is that these trial
dogs do work on commercial farms and can do all the jobs needed, as well as the
fancy stuff for the trials. They
have the genes to do everything needed so there is no worry. If they win at trials then they qualify
to enter the stud book of the New Zealand Sheep Dog Trial Association (NZSDTA). No useless dog can get into this book,
and a dog’s looks and fancy points don't matter. It's performance alone.
If you want to breed dogs that are not in
the stud book, then you should make sure the parents have performed well and
that you can see them working. But
remember you are trying to judge G, even if the handler has ruined it through
the E provided. In other
farm livestock, many a farmer has been duped by thinking he/she was buying G
when in fact they paid through the nose for E.
Check
the pedigree
Pedigrees are simply a record of ancestry -
and that's all. Never assume that
a "pedigree" animal that can be registered in a studbook is genetically
better than a non-registered animal.
This is where the New Zealand farm working dog is unique - they can only
get into the stud book by proving good working performance.
If a pedigree is a list of names and
numbers and has no record of performance - then it doesn't tell you much. The important feature of a pedigree is
that every time you go back a generation, then you halve the genetic influence
of the ancestors.
So parents give half of their genes (good
and bad) to their offspring.
Grandparents give a quarter, great-grand parents one eighth and so on
working backward along the pedigree.
In practice, only be concerned with a pedigree as far back as
grandparents, as each ancestor after that has so little influence.
Remember that if anyone is trying to tell
you that an animal's superiority is due to a particular great-great-great
grandsire, he has only provided one sixteenth of the genes. Does this mean that the other fifteen
sixteenth of the genes were useless?
Which would have the greater influence one sixteenth or fifteen
sixteenths?
Fortunately the working dog world is free
from a lot of the mumbo-jumbo about pedigree breeding that confuses other
livestock. We breed for
performance and "functional traits" in working dogs and it makes life
so much easier, and the end results more predictable. Thank goodness nobody yet has started to say what a
working dog should look like and formed a committee to administer this nonsense. But that’s not to say it could happen
in future.
Inbreeding
This is where "related" animals
are mated. This concentrates
genes, whether they are good or bad.
Breeders are often forced to inbreed when they want a sire for a
particular purpose, and they cannot find one better than their own. So they mate related animals and live
with the consequences.
There is nothing wrong with this, and it
will certainly concentrate similar genes.
In the process however, as similar genes meet, they may throw up certain
recessive genes that have been hidden.
It's here where undershot jaw, cleft palates, no hair, and drawfism is
seen. You can cull these out and
keep on inbreeding, but as the level of inbreeding rises (called increasing
homozygosity) you'll most likely find "inbreeding depression" taking
its effect.
Here traits like fertility, litter size and
general "fitness" are affected.
Bitches will be hard to get in pup, and they'll have small litters with
“runts”(small weak pups) in them.
In working dogs we euthanase them but in the fancy dog world they keep
them, often to form new breeds!
If you inbreed and strike trouble you can
get out of it in one generation by making an "outcross" to some
completely unrelated animal. All
those recessive problem genes will have been buried again.
So avoid high levels of inbreeding by not
mating sires to daughters, sons to mothers and even as close as first
cousins. Don't go any closer than
second cousins. First cousins have
common grandparents and this is generally too close, unless you have a very
special reason to experiment.
Linebreeding
This is very similar to inbreeding but
seems to have a better image among breeders. It's “inbreeding done more slowly” and has the same effect
as mating relatives and concentrating genes. This is the way to go - you make haste slowly, and it gives
you time to do some selection, and go back and make an outcross if you strike
trouble.
In this outcrossing, try to get a new sire
from a breeder with similar objectives but slightly different genes. Then you don't slip back too far and
lose the benefits of the genes you want.
People have a great fear of inbreeding
(probably because of the human religious taboo against it) but less fear of
linebreeding. So there's an old
saying that if it fails call it inbreeding but if it works call it
linebreeding!
The future working dog
The dog like the
human is a very adaptable species and it has a great future. It can reproduce
rapidly and responds well to natural or man-made selection. As a result there is plenty of
opportunity for man to change the working dog - for better or for worse.
The working dog
is by no means perfect - despite what some enthusiasts would argue. For example some people on today's
farms with the range of pressures that did not exist in the old days, say it
takes too long to train. Today's
shepherds don't want to spend hours after work and at weekends training
dogs. They want a quick learner -
to save time, money and food. And
they want fewer failures, which there are despite all the breeding wisdom. So there’s an interesting challenge for
breeders, geneticists and behaviourists in the future.
Some people are
concerned that the genetic base of our working dogs may be getting too narrow
with the influence of too few top animals. They fear some inbreeding depression which can be expressed
in less robust animals for the hard life on the farm, as opposed to the short
run at the trials. This fear has
come to pass recently with a rapid increase in the incidence of hip dysplasia
(HD). It has clearly been spread
by the popularity of some top trial dogs, through linebreeding to them.
There's
certainly plenty of technology waiting to be used in future dog breeding if the
breeders or the market demands it.
It has been here for some time.
Examples are artificial insemination (AI) to allow more people cheap
access to top genes, multiple ovulation and embryo transfer (MOET), egg
splitting to produce clones of identical animals, and embryo storage and
transfer.
We are now on the threshold of using
genetic engineering to move individual genes around. There has been little discussion on how genetic engineering
could be used in the working dog but the opportunity is there. Indeed the scientific community in the
past has shown little interest in the working dog in relation to its importance
to the economy.
New Zealand has a very high health status
in the world and could become a genetic reservoir and storage repository for
the world's top working dog genes - and that includes all dogs classed as
"workers".
There is no reason why New Zealand could not become the Mecca for
working dogs like we are for shearing.
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