Heterosis and its effects on subsequent generations

Discussion in 'General breed discussions & FAQ' started by Syerf, Jan 5, 2013.

  1. Syerf

    Syerf Out Of The Brooder

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    Hopefully someone with genetic knowledge can sate my curiosity on this subject.

    If two purebred lines are crossed and then their offspring are crossed and their offspring's offspring are crossed and so forth, how many generations will have some degree of heterosis/hybrid vigor? Or rather, how long till it dissipates to the point that they can't be distinguished from one of the original lines?

    Just to be clear when I say two purebred lines I mean the same breed but not directly related to each other.
     
  2. Ridgerunner

    Ridgerunner Chicken Obsessed

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    I'm not an expert but I'll take a shot. You lose some genetic diversity with each generation if you cross related birds. I look at heterosis as really good genetic diversity.

    How much you lose depends on different things. How are you selecting your breeders? Are you using a specific technique to maintain genetic diversity? Spiral breeding is one way to stretch it out. Another way is pen breeding where you have a lot of different roosters with a lot of different hens. The more roosters and hens you have, the better your genetic diversity. The pure randomness of the breeding works in your favor with pen breeding but it's not the way to breed show birds. The randomness works against you in that. Line breeding will knock out genetic diversity pretty quickly.

    I think there are too many variables to be able ot give you a hard and fast number. Part of that is the breeding techniques you use. Part of it is how good you are at selecting your breeders. I tihnk part of it is your goals. If you are breeding birds for show, you don't want that much genetic diversity. You want to enhance the traits that show birds should have and eliminate the others.
     
    Last edited: Jan 6, 2013
  3. Syerf

    Syerf Out Of The Brooder

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    Thanks,

    So if I had a large enough flock in one pen the degradation would be minimal?

    I was just looking at egg and/or meat production.
     
  4. gallorojo

    gallorojo Chillin' With My Peeps

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    If all you care about is meat and eggs, then just get a new cock each year, either of your chosen breed, but of an unrelated strain, or, of a similar but different breed. Then you will always have maximum heterosis, plus, you keep things simple. Not the way to breed show birds, but practical for farm production .
     
  5. nicalandia

    nicalandia Overrun With Chickens

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    the amount of Hybrid vigor found on stable breeds(old breeds, herritage breeds) is minimal. why? think about it they need to keep a SOP. a few of them are outbreeding to other breeds with simmilar body and type to regain or gain any vigor
    this is not the case with Showing lines. but vigor can still be kept with aggressive culling.
     
  6. Syerf

    Syerf Out Of The Brooder

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    My question was about how fast I would lose heterosis if I didn't add any new blood after the cross.
     
  7. nicalandia

    nicalandia Overrun With Chickens

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    that will depend on how closely related are your two lines..

    say if you cross a NH from an american breeder and UK NH. then you can go for many generations before you see any accmulation of bad traits. but then again this can be fix aggressive culling
     
  8. Syerf

    Syerf Out Of The Brooder

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    interesting, thanks!
     

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