Questions for the genetics wizards out there - Page 4

>inbreeding is not the problem , poor selection is.

Another aspect of heavy inbreeding is that within 3 generations you can almost completely predict what you can expect in offspring using basic genetics. I studied genetics for years through highschool and college, starting with fruit-flies, and eventually working up to more complex organisms like mice and rats. If you have a highly inbreed strain of well-bred individuals the biggest risk to your program is outcrossing, because you might introduce an incompatable trait. I bred parent x offspring, sibling x sibling for years and developed a strain of easily trainable mice with an average lifespan nearly double the standard mouse lifespan with no observable increase in health problems... however I also wound up anihilating everything with a single bad outcross, inadvertantly introduced a lethal gene, which completely destroyed over 5 years of work in one generation. D'oh!

Pigeons/doves are a more simple organism than a dog, and the emphasis here is flying ability and stamina. While, as I understand it, the lifespan of a racing bird is comparable to a GSD, the are a simpler organism overal, and smaller. Smaller creatures suffer less from certain structural genetic faults due to mass. Also, the aims of breeding say nothing more than two key abilities: effective flight and homing skills.

When function is the aim of inbreeding over appearence, the objective also remains more "pure" because if an animal cannot function in its task it will not be used for breeding. I know a breeder of racing sled dogs, not a purebred strain, but a mix of husky x greyhound, and something else. The dogs were heavily inbreed, but as temperament and physical appearence were not as important as stamina, strength and speed her dogs were remarkably healthy stock.

Compare that to the excessive inbreeding of certain American line GSDs where the emphasis is appearence, and physical form is secondary. Any time function is placed behind form in a close-inbreeding program the chance for physical defects is multiplied exponentially.

At least such has been my experience.

"Any time function is placed behind form in a close-inbreeding program the chance for physical defects is multiplied exponentially."

jc.Carroll:  Your complete posting is very interesting.  I particularly find the above quote from your posting interesting and thought provoking.  I am mulling over it, as it compares to the GSD.  Of course, the key words from the quote are "close-inbreeding program".  I doubt that this is done more than very rarely with the GSD, although FerrumGSDs illustrated quite well and detailed, in his above posting, that something close has been done in the past.

Still mulling, as it pertains to both dogs and my birds.  A knee jerk reaction from me is that the statement does not hold true for the birds but does hold true for the higher form, the dog.  I guess that was the point you made.

By the by.  There are some pigeon racers who hold that crosses make the better racers, and it sometimes shows in the race results that this is so.  However, there are many race results that also show that very close inbreeding also producers winners.  Just for info, even though pigeons are said to mate for life, most breeders who value their stock highly, keep individual pairs in individual cages, to insure no "hank panky" occurred.  I often wonder with both birds and GSD's, if a pedigree is accurate, as way back when (say great grandfather) an individual dog or bird, was gotten wrong (this has to have happened many times), would that "re-write" the pedigrees of almost all of the present day GSD's?  But, that may be a discussion for another day.  I guess a case could be made that it would not make much difference, because of the small gene pool of the GSD anyway.

"Any time function is placed behind form in a close-inbreeding program the chance for physical defects is multiplied exponentially."

I must confess my knowledge of avian genetics to be extremely limited...

It might not hold true for birds, but I know it holds true for rodents. One of my colonies was inbreed for appearence (color, shorter body, and rounder nose). Your show mouse has a long, narrow body and snipey nose. I found selectively breeding for color alone to be most detrimental (weakened immune system, shorter lifespan, etc) , but inbreeding for body structure w/out emphasis on health came in at a close second. Only when breeding specifically for health (longevity and temperament) did inbreeding not seem to produce detrimental results.

I believe avians are more primative. Reptiles even more so. I know that lots of pet snake breeders are producing "designer colors" and I've never heard of health problems thereof.  With extremely basic animals like fruit flies you can inbreed them, expose them to radiation to ensure new and creative mutations. I bred wingless ones because they were easier to work with; they didn't fly away. The only thing radiation affected was fertility.

Meanwhile, back to dogs I am given pause to think about the albino Doberman, which is a true albino not a pigmented white like the white GSD. The entire color started from a mother bred to her albino son. Albino dobes have all the problems that go along with typical albinoism (sight, skin, immune system) and that of a negatively inbred population. I learned that the average lifespan of an albino dobe is roughly half that of a normal dobe due to health complications. They also tend to have temperament and trainability issues.

I've been watching the "panda shepherd" phenomenon with like interest to see if they start to develope health / temperament problems at an accelerated rate as well.

Part of me would like to get one of these creatures to observe it first hand... but I can't bring myself to buy an albino dobe or panda shepherd and support such unsound breeding practices. That crosses the my line from ethical genetic study to unethical support of uncensored breeding emphasizing appearence traits only.

I always felt sorry for the fruit flies as, my understanding is that their life span is about 24 hours.  Do I have that correct?

As to your statements about breeding for color, etc. vs form, function and health.  They make perfect sense, common sense wise.

My problem right now is that I have purchased some heavily inbred pigeons (inbred to past top race winners), and I have to decide which way to pair up my birds.  In your opinion, even though you have not done much fowl research, especially concerning homing and speed ability, should I cross or inbreed even more?  My initial thoughts are to try both and see what races well, but that is what every other racing fancier does and I, because of my age and just now getting into the sport after a twenty-five plus year absence, don't want to spend thrity years "figuring it out". :)

If you were into racing homing pigeons, with your current knowledge and you had just five pairs of birds, would you continue the inbreeding back to the famous winners of their pasts, or would you cross?  Just curious.

Thanks for the compliments, Do Right *grins*

With fruit flies: 24 hours? *hehe* No, that'd be way too short for breeding any sort of breeding. The species I used, most common to genetics (Drosophila melanogaster) lives for about a month. Their generations are about 2 weeks in length. Mayflies (Ephemeroptera sp.) those live for 24 hours as adults.

>should I cross or inbreed even more?  My initial thoughts are to try both and see what races well, but that is what every other racing fancier does and I, because of my age and just now getting into the sport after a twenty-five plus year absence, don't want to spend thrity years "figuring it out". :)

Hmm... It depends on whether you are racing for a hobby or as a serious competitor. If you were doing it as a hobby, you could experiment with in/out-breeding and take your time developing a program. However, if you're in it for sport you don't really want to waste time playing with genetics, and want to get right down to maximizing your program's output. So, let's say you're doing this for maximizing...

I'd look back through as many pedigrees of top birds as I could get my hands on, see trends and count how many times a single individual appears in progeny pedigree to get an estimate of how many times they are bred back to the same lines. After looking through the pedigrees you'd see how many times they were bred around. Through pedigree research you'd also be able to see how often new outcrosses or more distantly related individuals were added to the lines. From there you could get an idea of what I call "terminal inbreeding capacity" -- which is the point where an individual's genetic make-up becomes too homogenous, and thus collapses in the next generation. I'd assume certain species have a higher capacity than others. The aforementioned reptiles don't seem to have one... but with dogs it appears to be around 30 years or less. It's based more on generation length than overal time.

I don't know if pigeons have this, but it would be good to find out. That way your wouldn't run the risk of your entire breeding program collapsing due to too-heavy inbreeding.

What I would do:

Are the birds monogamous or polygamous (if you mentioned that before I missed it) , because if they're polygamous that leads more oppertunites for broadening your base generation... But if they are monogamous... [A male-A female, Bm-Bf, Cm-Cf, Dm-Df, and Em-Ef].. If any of your pairs are closely related to the other pair you could save those for an F2 cross.

My knee jerk reaction is (after researching line- inbreeding of racing pigeons) to outcross for my F1 generation with previous winners, then breed back to my lines, and see what the F2 generation produces. If I needed, I could grand x offspring cross the parent generation which would give me line-breeding, but not too close. From there I'd have my F3 which hopefully would be large enough that it would give me the option of breeding my best uncle/aunt x niece/nephew, and cousin x cousin.

Personally it's my knee-jerk reaction to stay away from parent x offspring, sibling x sibling crosses unless one is truly familiar with one's lines... and that's generally something you don't develope until your third generation, in my experience. At that point in a line-breeding program most positive and negative traits should be expressed because by then the recessives should be drawn to the surface in at least some of the offspring, so you can identify what's carried but not expressed.

(ie, GSD coats -- not that I breed GSDs like this, but it's an example: [C = stock coat, c = long coat; cc = expressed long coat on puppy] CC x Cc = 50% CC, 50% Cc... with those odds there's a chance of breeding a Cc to another Cc and getting: 25% CC-no carrier; 50%-carrier, and 25% long coat by the thrid generation. A

... Continued

(ie, GSD coats -- not that I breed GSDs like this, but it's an example: [C = stock coat, c = long coat; cc = expressed long coat on puppy] CC x Cc = 50% CC, 50% Cc... with those odds there's a chance of breeding a Cc to another Cc and getting: 25% CC-no carrier; 50%-carrier, and 25% long coat by the thrid generation. And if you find a puppy has a long coat then you know both parents have to carry it, even if none of their parents or litter mates had a long coat.

Simply put, I'd go something like this:

• [starting pairs / 0] bred together = F1
• F1bred back to related winners = F2
• The best birds in F2 can be bred back to your best birds in 0 = F3

So then you could establish your foundation, which would be F2, and your F3 generation would be your first distinct line *grin*

JC Carroll

Thanks for this post, now I have to research what "generation length" is. It that age of sexual Maturity?

Got it! generation length is the age difference between Parents and Progeny

So this is 2 years in Dogs?

Hopefully, at least two years.  I have a few dogs that are 25 generations back to the founder Horand through different avenues in their pedigrees, so that would be a long term average of greater than four years (at least through the sires).  The female lines will generally be younger.

Wow, jcCarroll, you really know your stuff.  I am printing your posting out, so that I can study it point by point.  Taking your explanation into account, my initial reaction is to breed the males and females I have with some, but not a lot, of common ancestry, to each other.  But my birds that have almost identical ancestry, with just a couple of deviations, not to each other, but to totally different birds, from totally different lineage.  I could then breed the latters offspring back to their parents, assuming the parents are good racers.  That is the key, what turns out to be good racers and what doesn't, although it is not uncommon for a sister and a brother to be one and the other.  ie: the sister to be a good racer and the brother to not be good at it.  Additionally, some birds suck at racing (actually more like "average") but produce real good offspring.

No wonder it takes years (or a lucky break) to get to the top of the podium.

Thanks much for the lesson.

Okay, now I feel sorry for the mayflies, not the fruit flies.