Purebred dog breeding discussion for the broader population - Page 2

 I am absolutely NOT a geneticist, so I don't claim to be an authority.  But I am trying to learn, and I'm reading just about everything I have time to read.  I am both fascinated and concerned by this subject.

Re. "hybrid vigor":  I read an article (online FWIW!) that basically said the "vigor" exists usually only for the first generation of descendants - the sons and daughters... but not for the 2nd generation (the grandsons and granddaughters) and so on.  I'm not an expert but the argument sounded reasonable to me.  (Of course it was online, and you can't believe everything you read online!)  It was specifically talking about purebred dogs, and I think the reasoning was that the chances of adding recessive bad genes into the mix was high.  Since the bad genes were recessive (assuming one wouldn't knowingly breed bad genes i.e. dominant genes) they would be unlikely to "match" in the first generation.  But if one was to breed two such 1st-gen dogs to each other, there would be even more bad recessive genes to potentially "match" than if you just had the original set of recessive genes.

Does anyone else know the article I'm referring to, and what is your opinion on it?

Re. maintaining diversity and increasing "outcrossing":  I would think that very thing is discouraged by the powers-that-be that reward homogenous offspring.  ("homogenous" may not be the best term - I mean, the goal toward having progeny as identical as possible, and as predictable as possible.)

Just as an aside... there are many cases in nature of isolated breeding groups that limit the available gene pool.  People must have investigated how large a breeding group is necessary for maximum health.  Does anyone know what that is, and how the GSD breed compares?

I think I read a long time ago that cheetahs are at risk because they are essentially all 1st cousins.

I wonder what is the diversity of the gene pool of the Chincoteague ponies?

I guess none of us would be here if we didn't have recessive and mutant genes that we relied on from the time we were nohing but a bunch of amphibians, LOL!

What is the difference in breeding a deaf dog and breeding a dog that if you take it off the property it has its tail tucked under its belly and that worried look in their eyes. Isn't breeding a dog like that STUPID!! Well guess what, there are very few people in the country breeding deaf dogs, there are hundreds of German Shepherd breeders in this country that are breeding these shy, totally useless specimen. Notice I have said nothing about show or working....that's not the point unless this type of dog has a high level of incidence in any type. The point is why aren't we as indignant of the empty caricatures of a GS that is being bred everyday in this country. And guess what...the reasons the dog is in that kind of mental condition is the same as the OP. Excessive linebreeding for long periods of time thus having little genetic diversity which eventually leads to extinction unless man props it up. Wake up people!! This shit is real!!!

Hybrid vigor is directly related to heterosis - which describes the degree to which the gene pairs consist of different alleles vs the same allele.

Simple example:
A tabby cat- because "tabby" is dominant - can be homozygous for tabby or heterozygous.
Homozygous: A-A (Lets just say A stands for agouti and little a stands for non-agouti)

Heterozygous for Tabby: A-a

A solid color cat, let's say black, can only be homozygous for non-agouti (otherwise it would be tabby): a-a

Dogs have many genes. Each gene is made up of a pair.

So, the First generation of an outcross of two unrelated dogs will show hybrid vigor because many more of their gene pairs will be made up of different alleles (by chance). Hence a state of heterosis exists and the individual will exhibit hybrid vigor.

The second generation could have as much heterozygosity - if again bred to a totally unrelated dog but- often 1st generation dogs in these experiments are bred together - hence lower heterozygosity in the 2nd generation.

For the person looking to read about this stuff- check out an articale called:
Purebred Dogs into the 21st Century written by Jeffrey Bragg -
It's detailed and serious yet easy to understand for the layman. You can google it.

I love this article and when I read it in the late 90s a light bulb went off in my head!

 Trafalgar:

That sounds similar to what I read.  So does that mean that hybrid vigor can be continually achieved if one always outcrosses?  How close can the mating pair be related in order to still be called an outcross?  E.g., would you have to go outside the breed, for a young breed like the GSD?  Or, on the other extreme, can it still be called outcrossing (to the extent required for hybrid vigor) if one is staying within, say, German show lines?  or working lines?  etc.

Would it be safe to say that one should *either* mostly outcross, *or* practice responsible informed line-breeding, since line-breeding outcrosses may be worse than line-breeding?  Is that what this statement is saying:

"The second generation could have as much heterozygosity - if again bred to a totally unrelated dog but- often 1st generation dogs in these experiments are bred together - hence lower heterozygosity in the 2nd generation."

Jayne:
I am not a breeder of GSD - and as such I am unaware of the average COI (coefficiency of inbreeding) in the average specimen within the breed. But if you will be making breeding choices for this breed you should definitely research these averages and certainly one of your criteria for any breeding should be to produce a litter that has a lower than average COI.

Google COI coefficient of inbreeding and read about it. (Basically it calculates the degree of shared ancestry).

COI software is available because what is a simple one minute job of calculations for a computer would take many hours for a person with a pencil.

Linebreeding isn't a term used in the scientific community because it is the same thing as inbreeding (just not as tight). It's a good idea to give up the term and use the word inbreeding instead. One could qualify the difference between extremely close inbreeding and inbreeding in general.

I personally believe "linebreeding" should be completely abandoned and assortive mating (mating dogs that are unrelated but have the desirable characteristics) is the better way to go. VERY few successful breeders would agree - because they are successful the way things are now!

Fortunately, the GSD breed is numerous enough in individuals to find unrelated dogs within the breed.

Unfortunately it will be a hard task to find unrelated dogs within narrow "lines", i.e. German Highlines, or Czech working lines, etc...

Certainly, the idea I most wish to be embraced is that the breed should be allowed to have as much variation as possible among all non-essential characteristics -and- that what is considered essential should become a much shorter list.

Obviously, health and a very low incidence of genetic disease should be on the short list along with a few things that make a GSD different than other breeds.


Personally, I'd like to see MUCH less consideration given to physical conformation and NO consideration given to beauty.

I think we are all forgetting that the gene pool is limited to the number of dogs used to create the breed in the begining,  those are the only genes available within the entire breed.  Specialization though continued line breeding to develope the show line, american line, working lines ect,  segregated some of these genes so that the dogs have a differnt identifyable phenotype.  The only way to get a true outcross and fully shake up the gene pool is to violate the sacred idea of working to working and show to show and re-mixing all of the lines.  Many will not do this because they like the type they have and beleive this will create a lot of unwanted poor puppies.

Linebreeding is not the curse of the breed, linebreeding develops type and insures continued passage of the correct traits to the offspring.  If the health problems were ultimatly breed out by being able to identify them prior to breeding a pair, we can get a better healthier stock.  Nature ensures this in wolf packs, herds of wild horses ect..  They naturally inbreed based on the pack and herd pecking order.  Very rarely is new genetics introduced by a new member outside the pack or herd.   The only way a new male gets in is to defeat the alpha male or stallion.  When this happens it is typically a son of the current pack leader/stallion.  Nature takes care of the mistakes.  Man does not do this with his creation, the purebreed dog.  We screw it up by limiting the origninating stock and breeding dogs that should not be breed.

One question for the board, how many of you have compared five generations of your family tree to your spouse??  How many of you even know the identity of these individuals??

Jayne:
I am not a breeder of GSD - and as such I am unaware of the average COI (coefficiency of inbreeding) in the average specimen within the breed. But if you will be making breeding choices for this breed you should definitely research these averages and certainly one of your criteria for any breeding should be to produce a litter that has a lower than average COI.  

Sorry, I thought we were just discussing things philosophically.  I'm not a breeder.  I'm also not a geneticist but I *am* a scientist; and as a scientist, I just *love* these types of discussions.

Like I said, I'd also be interested in applying this discussion to cheeetahs, or the Chincoteague ponies... or those Siberian domesticated foxes, if you've read about that experiment.  IIRC (If I recall correctly) those foxes started demonstrating droopy ears and white blazes on their faces, after just a few generations of selected breeding based on friendliness toward humans.

I also read that elephants are the only wild animals that have droopy ears.  All other droopy-eared animals are domesticated.

Also, wild mice are almost always solid colors; only domesticated mice exhibit non-solid colors.  Wasn't it in the panda discussion that I read that?  Sorry, it's late and I'm too tired to go look it up.

I personally believe "linebreeding" should be completely abandoned and assortive mating (mating dogs that are unrelated but have the desirable characteristics) is the better way to go. VERY few successful breeders would agree - because they are successful the way things are now!   

I think I read somewhere (I hope I'm not accused of not being original!!) that linebreeding is used because it more quickly achieves predictable and uniform progeny with any chosen desired traits.  Continuous outcrossing would not quickly "fix" certain characteristics - say, B&T saddle.  Just for example.  From what I understand, as an armchair geneticist (i.e., *not* a geneticist).  I'm not advocating selectively breeding for B&T saddle.  Just saying what I read was the argument in favor of linebreeding - or inbreeding to a greater or lesser extent.

Fortunately, the GSD breed is numerous enough in individuals to find unrelated dogs within the breed."

But aren't they all ultimately descendents of Horand?

  "Certainly, the idea I most wish to be embraced is that the breed should be allowed to have as much variation as possible among all non-essential characteristics -and- that what is considered essential should become a much shorter list.

Obviously, health and a very low incidence of genetic disease should be on the short list along with a few things that make a GSD different than other breeds."

 

I'm not arguing with you there.

 

One question for the board, how many of you have compared five generations of your family tree to your spouse??  How many of you even know the identity of these individuals??

 Very interesting question!  No I don't know my family history back that far... but that would be an interesting exercise!