March 1, 2016

New Zealand Farm working Dogs. 7. Genetics and breeding

--> By Dr Clive Dalton

 

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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