Breeding for breeding stock

[Cas]

I've been wondering generally how many inbred generations you can have with cornsnakes before one starts to notice problems. I mean, it's common practice to take 2 siblings het for a desired trait and breed them to get homozygous offspring... is it a problem then to take 2 snakes out of <i>that</i> pairing and breed them?

<table border=0><tr><td width="15">brother</td><td width="5">X</td><td width="15">sister</td></tr><tr><td width="15"></td><td width="5"><font color="red">|<br>V</font></td><td width="15"></td></tr><tr><td width="15"><font color="green">brother</font></td><td width="5">X</td><td width="15"><font color="green">sister</font></td></tr><tr><td width="15"></td><td width="5"><font color="red">|<br>V</font></td width="15"><td></td><tdwidth="15"></td></tr><tr><td width="15"></td><td width="5"><b>F2</b></td><td width="15"></td></tr></table>

Are genetic defects/weaknesses going to start showing up in the F2, or can it go more generations? Or, would be better (and more time consuming!) to breed the first set of offspring out to other animals (instead of breeding them together to get the F2) and get hets, breed those hets to siblings to get the trait in queston from two sets, and then breed those sets together as breeding pairs?

<table border=0><tr><td width="15"><font color="green">brother</font></td><td width="5">X</td><td width="15">new</td> <td width="15"></td><td width="15"><font color="green">sister</font></td><td width="5">X</td><td width="15">new</td></tr><tr><td width="15"></td><td width="5"><font color="red">|<br>V</font></td><td width="15"></td><td width="15"></td><td width="15"></td><td width="5"><font color="red">|<br>V</font></td></tr><tr><td width="15">brother</td><td width="5">X</td><td width="15">sister</td> <td width="15"></td><td width="15">sister</td><td width="5">X</td><td width="15">brother</td></tr><tr><td width="15"></td><td width="5"><font color="red">|<br>V</font></td><td width="15"></td><td width="15"></td><td width="15"></td><td width="5"><font color="red">|<br>V</font></td></tr><tr><td width="15"></td><td width="5">new</td><td width="15"></td> <td width="15">X</td><td width="15"></td><td width="5">new</td><td width="15"></td></tr><tr><td width="15"></td><td width="5"></td><td width="15"></td><td width="15"><font color="red"> |<br>V</font></td><td width="15"></td><td width="5"></td></tr><tr><td width="15"></td><td width="5"></td><td width="15"></td><td width="15"><b>kids</b></td><td width="15"></td><td width="5"></td></tr></table>

Or is there a better way to go when starting out with only 2 related foundation animals?

Dawn

[Rachel]

I asked a similar question on here and to various collegues. I have been given mixed answers (NEVER breed siblings to its fine to do so). The way I see it it that its OK to breed siblings but not excessively down generations. Thats just theory...maybe someone here would be able to give you fact??
HTH anyway! :)

[Shaky]

There IS no definite answer. It depends on the genes of the parents.
Lets say that a snake has, for instance, a wild, unpaired gene for a lack of eye formation.
If that gene is never paired with one to bring it to the phenotype, you'll never see it.
However, the gene for kinked-ness is more common(there are more carriers for this trait), therefore, some snakes are born with kinked backs. Also, how can you be sure that the first abnormality is not stress or husbandry related? it takes several breedings (years) to see if the "bad" gene does prove true.
Many times in the wild, a malformedsnake will die quickly, thus eliminating the phenotype from the population.
All this said, if you hit the right combo, deformities will spring up happily.
And, the more you inbreed, the better chance you have of seeing recessives.

[Kat]

Well, assuming the negative mutation is a recessive gene that only one parent carries, the earliest you'll get it showing up is in the F2's. The odds are the same as getting a lavender if you were to take a snake het for lavender, breed it to a normal, and then breed those hatchlings together.

If you breed an F1 back to the parent with the bad gene with one copy of a bad gene, then the offspring of that pairing are atleast 50% possible het for the bad mutation, and if the F1 you're using also carries the bad gene, then your odds increase of getting one copy, and you can even get both copies.

If we assume that any bad trait that shows up in offspring produced by a breeder is culled from the stock before any hatchlings are sold to the public (which isn't always true... but for the sake of this arguement we'll pretend all herpers are responsible), then we can assume that the only chance of a bad trait appearing is due to recessive genes. Ergo, a particular snake is at most het for the bad trait as an unhealthy snake would have been culled already. So... we buy a brother and sister of a clutch. For any particular bad trait, they're at most het. If both of their parents were het for that bad trait (worst possible case as homozygous ones are culled), then they've each a 66% chance of being het for that bad trait. If only one parent was het, then they've each a 50% chance of being het for that bad trait. Obviously if neither parent was het for that trait, they both lack it as well. Someone might want to check my math, but if the odds of the four combinations of parents (het/nothet, nothet/het, het/het, nothet/nothet) are equal, then there's roughly a 41% chance of any particular snake having that bad gene in the F1's. I sincerely doubt the odds are equal though... Depending on where you're looking, certain populations may have a greater chance of having the gene than others.

It's anyone's guess, really. :)
-Kat

[Shaky]

These really disabling mutations that we're talking about don't seem to be simple recessives, since often only an inordinately small percentage of a clutch seem to be affected. Its like a rider gene that only occers if a combined # of other alleles fall a certain way.
Still difficult to project.

[Cas]

Thanks... I understand the theory behind the accumulation of genetic anomolies that can come from inbreeding... (Shaky, likely that is what it is.... a number of genes all have to be homozygous recessive before those major effects are evident) I guess what I'm really wondering is what the average # of generations is that cornsnakes can go without detrimental effects.... it does seem that some animals are more likely to have difficulties sooner with inbreeeding/line breeing than others, generally having to do with the sheer #s of genes and therefor the number of hidden recessives that could be present.

And, to boil it all down..... what's the most effective strategy for developing a wider breeding stock out of only two individuals who are het for a trait? Or out of only two individuals who are displaying a desired recessive trait (eg, if you only have 2 amels)?

[UTWolfe]

If the lineage of a snake is unknown is there anyway to figure out if it is het for anything besides breeding?

[Darin Chappell]

"If the lineage of a snake is unknown is there anyway to figure out if it is het for anything besides breeding?"


No, not for certain.

However, many bloodred outcrosses are very red in their coloration and have distinctive ventral checkering patterns. Of course that brings up the old "Can a snake be het for bloodred" argument. I have also had some say that animals het for some strains of motley tend to have an effect on the F1 appearances, but I can't clearly recall who said they had noticed such.

Clint B., perhaps?


:confused:

[vanderkm]

Hi Dawn,
You pose some interesting questions and I can't respond from knowledge of cornsnakes, but do have a couple ideas to share.

Besides uncovering hidden detrimental recessive genes with inbreeding, it is worth considering the depression of vigor that is associated with inbreeding and in mammals at least, seems to have most impact on the ongoing reproductive performance in females as the degree if inbreeding increases over several generations.

To perpetuate a recessive trait if you have only two siblings that show it, you might want to consider using the male to greater advantage by breeding him to several females, including the related one. All offspring from the breeding of siblings would produce snakes that show the trait, but were inbred. This clutch could be the source of a couple males for the next generation.

The outcrosses to normal females (unrelated to him and each other), will produce 100% hets which will have the advantage of hybrid vigor, and that has most impact on maternal characteristics, such as fertility. Keeping females from these outcrosses (het for your desired trait), and breeding them to the inbred males will give you quite a bit of genetic diversity in your next generation, along with 50% of the animals showing the desired trait. The offspring from the third generation can then be bred back to a brother that was not their sire (their uncle, or their grandfather) and you could be producing a very high percentage of the desired trait, while still maintaining a relatively low level of inbeeding because of using multiple females in the first generation. Continuing this process, using your second generation males on other normal females, and then rotating your crosses, will let you keep inbreeding down - the only real risk is if the original male carries some very bad genes that will be concentrated over time with this approach and come back to haunt you in the future generations.

I would also be very interested to know if breeders have had success with more than 2-3 generations of sibling breedings. Know it works fine in poultry and mice, but haven't read much about it in corns.


Just some thoughts,

Mary v.

[bmm]

For answer to if breeding brother to sister has been sucsessful just look at any cornsnake other than normal!

Most all morphs had to be inbreed originally to achieve the look they have today.


bmm

[Shaky]

If you really are looking for an average of generations which result in deformities, you'll just have to go on a guess.
My guess: 4-5 generations will start showing a lack of fertility or deformities.
It could take more or fewer, depending on tons of things.

[Rich Z]

One of the things that many people don't consider is that there might be something wrong in the husbandry of the animals that is not immediately detrimental, but might be so if cumulative over multiple generations. Take, for instance, some amino acid that is lacking from the diet in the original parents. It may not show any effect at all. And then maybe not through the next couple of generations. But each generation is exhibiting a gradual weakening of some function that requires this amino acid to work properly. You just can't see it yet.

When you finally get to a generation where the lack of this amino acid finally begins to exhibit itself noticeably in the offspring, many people would be quick to point to inbreeding as the culprit, when it actually may not be the case at all.

How many of you give your animals vitamin supplements? Mineral supplements?

If inbreeding was the bugaboo that everyone labels it to be, why did life even remain on places like the Galapagos Islands after many generations of some animal forms being virtually isolated from any other influx of genetic material? Why didn't they all die out from inbreeding?

[Shaky]

Take any random clutch of eggs from which deformities arise.
Its pretty rare that you get 100% wierdos. The seeming healthy ones from the clutch WILL go on and reproduce, creating more healthy ones and some deformed ones.
There will still remain a percentage of genetically healthy, normal offspring. It would be very hard to get rid of the dominant genes needed for survival.
Also, I'm sure that there WERE many critters who died off due to inbreeding on the Galapagos and other isolated spots, but how would we know?
(just something to chaw on)
-Jack

[Cas]

Thanks Mary, that was exactly what I was looking for! :) (seems so obvious <i>now</i>.... ;) )


Inbreeding is one of those things that's hard to work out - look at cheetahs... they've had multiple genetic bottlenecks in their history, and because of it it's very hard to get viable offspring from them. And then there are other animals who have populations that are highly inbred and they're fine, and are well adapted to their environments (however, if something changes, it's going to wipe them all out, because there's no diversity - there are no few animals that may survive or thrive in the new conditions). There was a calculation for the % of genetic diversity/unrelated immigrants to a population needed to keep it from bottlenecking, but of course I can't remember it anymore.

And, of course, it's harder for people to effectively line-breed/inbreed animals, simply because we don't have as big a starting population to work with that nature frequently does - and in the wild, a lot of the critters we nurse along through their stubborn periods wouldn't have made it - and any "bad" genes they carry would get cut out along with them. People don't select for 'survival fitness' nearly as well as nature does.


Dawn (who has a headache and thinks this post probably doesn't make any sense!)

[Rich Z]

Hmm, what does it say about the human race if we all originated from Adam and Eve? ;)

Inbred, all of us.............

[Axe]

I knew there was somethin' funny 'bout you Rich ;)

[vanderkm]

The development of breeding programs remains an area of great interest and I think there is some responsibility of breeders to include a natural type selection in their program in addition to the color or pattern characteristics they are looking for. While there is no problem with saving a weak baby in order to place it as a pet, I don't think it is one I would want to keep as the foundation of a breeding line, unless I made plans to counter act that weakness at some point down the line.

I do think the post made a lot of sense and there were many interesting replies.

Mary v.

[Shannon Hiatt]

Good thread. I'm sorry that I am jumping in late (as I usually do, being a professional forum lurker), but have a few observations.

First, when I start a breeding program with any snake species, I try to get a broad base of bloodlines with which to work. That isn't always possible, but I believe this is one of the best routes to preclude problems down the line. I know, I know. Depends upon the pocketbook too.

Second, how long have Colubrids been around? I forget my snake prehistory, although I was just a baby back then, but 10 to 15 million years comes to mind. And remember that some species spend an entire lifetime in, on, or near the "home" rock pile--I am thinking of some California Mountain kingsnakes now. I'm sure you can think of others. And, yes, I know that the wayward young males spread out while the females stay closer to home, but a few find their way back to the ideal habitat of the same rock pile. Hmmmm, 10 million years of inbreeding. Makes F2 and F4 seem insignificant.

Third, it is because we have dabbled with the genes we find attractive that often sets our snakes up for inbreeding problems WHEN severe selection isn't part of the equation. I offer a line breeding program for those interested in such mental exercises at my Quality reptiles, Texas web site:

http://www.qualityreps.com/rotational_line_breeding_program.htm

This line breeding program is based on my many, many years breeding performance pigeons and show bantams. Snakes are closely related, no? And I like to work matings on paper as much as I like the actual process.

Finally, remember Rich's story on the lone egg that hatched and produced the lavender that started it all! Let's see, that means ALL lavenders in existence are bred from that LONE lavender (unless an independent new lavender gene popped out of someone's breeding program we are NOT aware of).

In any event, I found this thread stimulating even for an old fart with few brain cells left. Thanks.

Shannon Hiatt
Quality Reptiles, Texas

[vanderkm]

Interesting perspective Shannon, and the rotational breeding scheme on your web site is, I agree, a basis for many sucessful breeding programs, especially in livestock. Works well as long as you can manage a large number of animals to maintain it. I used a similar program to play with genetics in my feeder mice, and it produced a line with distinct color, that still had the advantage of bringing in the vitatility of pink eyed whites.

I am suprised by the negative attitude toward inbreeding in many breeder discussions, because while it does tend to uncover hidden recessive genes, it is also the best method for fixing traits in a line of animals. Uncovering the recessives is also how the neat color variations in corns turned up. I think that at some stage in a breeding program, inbreeding is very beneficial as long as combined with strong culling, because inbred animals have a far greater probability of passing on their desired qualities, especially those that are controlled by multiple genes. They are more uniformly homozygous, so their appearance is a better reflection of their genetic potential.

I found Rich's point on cummulative husbandry problems a very interesting one, and something I think is rarely accounted for. It may really be the source of many problems that have been attributed to inbreeding. There is so much that we don't know about captive reptile husbandry relative to domesticated species like livestock and pets, that makes developing breeding programs so much more challenging.

Just one additional point, Dawn, that occurred to me after I posted last time, and that is if you are going to breed a unique male to unrelated females to diversify your line, you might want to consider using girls that will give you a maximum number of het genes in your first generation. You have likely already thought of that, but I think it would be much more interesting to breed, for example, a lavender male to hypo, snow, striped or blizzard females than to normals, because your first generation will be het for so many genes rather than just het for lavender.

Best wishes for 2003 to all,

Mary v.

[Shannon Hiatt]

Mary -- ah, feeder mice. Funny how they become a side project for those of us with curious natures and the prediliction to work with just "one" more species. When the 9/11 aftermath hit my profession, I had to divest myself of all snakes, fancy feeder mice, and fancy feeder rats. I, too, was not content to have white mice and rats. I had to have patterned mice (try that project sometime Corn breeders!), lavenders, etc. The rats were not too far behind that mania. The snakes are back but I have decided to spend more time with them and less with feeders of any species.

And I am working on paper the plans for my Corn projects--lavender, of course. I'll use a three male rotational breeding program, with two females per male. I disagree that it will take large numbers of breeding animals, however, as the beauty of a rotational program is that I MUST select the best three males and the BEST six females to carry on the project. I don't keep the older breeders. They are sold. Yes, if I have TWO programs of the same cultivar going at the same time, then I have six males and 12 females. That's getting out of hand even for me. So I keep it at three and six for the duration. Nine Corns are plenty to keep me busy.

And your notion of doubling up the genes in the females is right on target. I'll keep the males lavenders of some sort--Hypo Lav, Lav, Opal, but will make sure the females are normals or Hypos het for Lav, Stripe, Motley, Amel, etc. Much more fun that way.

I agree that inbreeding gets a bum rap when the problem lies with our reluctance to select only the best of the best or when it is in our husbandry methods. How many kinks are temp related and NOT genetic? I'd hazard a guess that I am more to blame for some anomalies than any genetic factors.

I also understand that it is hard to eqate a breeding program for birds and mammals with those we might use for reptiles. Hence my notion that snakes have had a few million years to evolve into the magnificent creatures they are. Mice inbred for twenty generations full brother and sister warrant a "strain" designation. No one has, to my knowledge, ever dveloped a strain of snakes. Rich isn't old enough. And I won't live long enough. But I am going to have at those Lavender corns from him and see what I can do in my little snake room in Texas. I'll be back to see what the real experts are doing on this forum.

Best wishes for a great breeding season in your snake room and in your feeder mouse colony. Mine are strictly of the freezer type these days.

Shannon Hiatt
Quality Reptiles, Texas