Clarificaiton--Crossing parent to offspring vs. crossing 2 siblings

[Amer]

Yup. So inbreeding can be bad, but it is also good and totally necessary to create a consistent strain with the traits you want.

 

[sdm111]

I have a pair of Harold brown Grey gamefowl a friend gifted. I kept 2 pair of their offspring. They are paired up now but in the spring I'll trade one from each pair with someone to bring back vigor and get them a little bigger.

 

[NatJ]

I think this is what I meant to ask. Let's just say in an absolute worst case. It's the Apocalypse, and you have exactly 1 rooster and 1 hen. You make the first cross (the only cross you can make). In the next step, would it be more wise to cross the siblings, or to cross the parent to the offsping? Some sources I read made a point that the parent/offspring cross was less prone to genetic problems. But it isn't clear to me why it should make a difference.

In that case, why choose between them?
Breed some daughters to their father.
Breed a son to his mother too.
Breed some sons and daughters to each other.

Hatch a bunch of chicks, then grow them up see how they do. Keep the best from any and all of them, make a note of which pairings produced how well, and eat the worst 90% or so.

If one of the original parents has some bad trait, you are more likely to see it in chicks from backcrossing to that parent, somewhat likely to see it in chicks from a sibling mating, and least likely to see it in the backcross to a non-affected parent. (Of course, there might be other bad traits that originated from the other parent.)

 

[DarJones]

Why is sibling/sibling mating potentially riskier than parent/offspring mating? Parent/offspring mating is always related exactly 50%. Sibling/sibling mating has the potential to be anything from 0% to 98% meaning that the siblings potentially can share a much higher percentage of genes. On a statistical basis, the siblings will be related at the 50% level just like the parent/sibling relationship. But with sibling/sibling mating, there is always the potential the chromosomes segregated so that more genes are identical and therefore more genetic defects have potential to express. Why 0 to 98 percent? Because one has to be male and the other female. The extra 2% is because a female chicken has ZW chromosomes while the male has ZZ. Therefore only 98% (approximately) of the remaining genome has potential to express inbreeding effects.

Not calling anyone out, but there are several errors posted in this thread. Please take a close look and ensure accuracy where possible! This includes anything I posted if anyone sees something incorrect!

 

[RayBoles]

I've read in a number of sources that inbreeding 2 siblings can be employed to try and stabilize some desirable trait, but that used extensively, offspring can start exhibiting unwanted characteristics (immune system health, physical health, etc). Three sources said that breeding a parent to an offspring was safer in the long run.

I'm curious if someone could comment on this. I realize the very safest way is to not cross closely related animals in the first place, but I also realize that inbreeding is very common when developing new breeds or stabilizing a trait within a breed.

I'm just trying to learn more about breeding, and in particular, how people go about breeding when they are trying to bring something back from the brink of extinction. Those cases where there are just a few birds left.

Thank you for any insights.

I breed brother to sister for 20+ years and according to genetic had a COI of 98.6. There were no problems and with selective breeding and mutations were actually improved. I have also read that subjects that were breed in this manner that didn't have problems were excellent in every way.