It’s always sad when well-meaning people embark on a doomed effort. Current attempts at breed preservation are a good example.
Breed preservation is a very simple task. The goal is to take the surviving remnant of an old breed and maintain it so that it retains whatever fraction of its genetic diversity still remains. This is fairly easy to do with chickens, which are reasonably inexpensive to keep in the required numbers. Basically, the technique is to keep several hundred individuals and do random matings, with no culling and no attempt at selective breeding. This can maintain the breed, unchanged, indefinitely. That’s what preservation is all about.
Selective breeding is the opposite of this: you breed only from selected individuals. With each generation, your flock becomes less representative of what you started with, and becomes something new instead. (Quite possibly, it becomes extinct through inbreeding.)
Sadly, groups like the American Livestock Breeding Conservancy just don’t get it. In their breeding guides, they are heavily into selection and culling, which is the worst thing they could do. Sigh.
This is the sort of thing that causes poultry scientists to periodically call for an effort to do it right. Selective breeding has caused commercial strains to lose about 50% of their genetic diversity (I’m surprised that it isn’t much higher). Conservation organizations like the ALBC aren’t helping, because they, too, are heavily into selection. So far, government attempts at breed preservation have always seemed to fail as soon as budgets became tight.
The remaining option is probably for someone to endow a foundation with enough money to acquire several dispersed facilities and hire some geneticists to acquire stock and manage the breeding program. The methods of breed preservation are well-understood by geneticists, but apparently not by anyone else.
This would be a very cool thing. I’d contribute my share.
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I think you’ve missed the boat completely on this one.
Breed preservation must be done with selection for the same characteristics that were used to originally develop the breed. NOT just genetic diversity, although that is important. You have to also look at the historical uses of the breed, the selection pressures that resulted from those uses and work to replicate it. So just keeping a large number of animals and breeding from them randomly will no more preserve a breed than will heavy inbreeding preserve it.
Random mating is not breed preservation and will never be no matter how many animals you use.
Even wild populations are not truly random mating, they all respond to some selection pressures.
A proper breed preservation program uses enough animals to maintain appropriate levels of genetic diversity while still selecting from the population those animals that conform to the uses of the original stock.
As a simple example, you cannot breed Black Welsh Mountain sheep (my sheep breed) and keep the occasional animal with white and maintain true to type. Abbey records indicate that those lambs were culled in the middle ages (our first written documentation of the breed as a separate breed) and they should be culled now. Yes, they represent genetic diversity but keeping them is at odds with how the breed was developed originally.
I think you are completely misunderstanding the goal of preservation of breeds.
I think people over-estimate the amount of selection that needs to be made to keep a breed true to type. For example, Production Reds and commercial White Leghorns haven’t been bred for appearance in over fifty years, but they still look like Rhode Island Reds and White Leghorns. You can take your hands away from the controls, and the breed will continue on autopilot — and with very little inbreeding.
If there’s a troublesome recessive, like with the occasional white sheep, removing the offending individual from the breeding pool won’t increase the amount of inbreeding much. Go ahead. What the heck. Similarly, flock matings (letting the individuals make their own arrangements) are easier than random matings, and work almost as well from a statistical genetics point of view.
I think the goal should be to preserve the gene pool unchanged. The USDA’s National Clonal Germplasm Repository is down the road from me. They preserve plants through cuttings and other means that allow strains to be preserved unchanged indefinitely. It’s harder with livestock, but it’s an important goal.
Which is not to say that other ways of keeping animals isn’t also good. I’m just saying that we should bite the bullet and add full-up, no-holds-barred, long-term, time-capsule-like preservation to our bag of tricks.
Inbreeding is not bad. Inbreeding without culling is bad. Breeds are developed with inbreeding and in fact the definition of a breed is one whose members resemble each other, sharing genetic makeup more than they resemble other groups. That is only done through inbreeding, the mating of more closely related individuals compared to the average.
As to capsule like preservation, the NAGP has a huge collection of germplasm from all sorts of animal species and in fact are working on techniques to freeze poultry eggs as well as semen to preserve the female line as well.
BUt cryopreservation is not breed preservation. Only if the animals and plants are used in ways similarly to their developed uses are they actually preserved.
We may just have to agree to disagree.
To me breed preservation is not save what we have with no changes or selection but save the entire package, use, appearance, production etc. that make up the diversity. It also requires saving the diversity of ways to manage agriculture not just a breed.
You can no more save or preserve a free ranging poultry breed in an enclosed environment than you can preserve a modern hot-house type breed in a free range situation. They will by necessity adapt to the conditions. So you have to keep conditions similar and selection similar to the original purpose and development to actually preserve a breed.