inbreeding

tobit

Songster
6 Years
Jan 1, 2014
428
47
103
UK
So I have 2 cream legbars (Rees line) that I obtained from a local breeder, I believe the eggs they hatched from were from a breeding group of 1 rooster with 3-5 hens, so they could be siblings or half-siblings. I was wondering if I could hatch any of the pullet's eggs, or if this would be too risky in terms of deleterious alleles showing up? I find it odd that father-daughter breeding is much more accepted than sibling breeding, even though the relatedness is the same!
 

tobit

Songster
6 Years
Jan 1, 2014
428
47
103
UK
You can. Father-daughter/mother-son mating is not the same. Siblings share identical copies of genes. Father-daughter only share half.


Okay cool! I'm not so sure... Say there are 2 offspring, for each gene, each offspring receives one gene from its father (1 out of 2 genes the father possesses) and one from its mother, the chances that both offspring receive the same gene from the father is 1/2, and the same for the alleles of the mother, so half of the alleles of the offspring (roughly, as this is due to chance) are the same. Whereas the parent-offspring relatedness is exactly 1/2 (due to the segregation of chromosomes during meiosis)... So to my knowledge siblings share roughly half of their alleles
 

JeanR

Songster
10 Years
Jul 6, 2009
434
177
191
Montana
;Do not be "afraid" of inbreeding--any relationship. For the next generation, you have time to locate another male, from one of the breeds in your mix. From the same pen they came from, is okay! The best chickens of all breeds are closely related. You will see the expressions of past generations, and if they are good layers, this will not be lost. Not to worry!!!!!!!
 

nchls school

Crowing
6 Years
Apr 22, 2015
6,892
3,630
386
Tennessee
So I have 2 cream legbars (Rees line) that I obtained from a local breeder, I believe the eggs they hatched from were from a breeding group of 1 rooster with 3-5 hens, so they could be siblings or half-siblings. I was wondering if I could hatch any of the pullet's eggs, or if this would be too risky in terms of deleterious alleles showing up? I find it odd that father-daughter breeding is much more accepted than sibling breeding, even though the relatedness is the same!
Inbreeding, I believe, is often used in achieving desirable traits. However too much inbreeding will eventually weaken breed lines.
 

JeanR

Songster
10 Years
Jul 6, 2009
434
177
191
Montana
Inbreeding is most always used to keep the desirable traits in every breed. The 100000s of chicks that hatcheries breed and sell for egg laying or fryers are well inbred for the best layers obtainable and/or for quick growing birds for meat. The flocks they come from are flock bred and no individual records of various breeding birds. It is possible to use these birds for breeding for YEARS, with new stock introduced, partially, and the "new" stock is not a guess, but well identified closely bred birds to continue their successes without a skip in their usefulness. They could not afford to "guess" what next year's chicks will produce when mature. The crosses that produce those egg layers, are indeed related and not 'guesses. Purebred chickens for Show birds, bred to a Standard, are also inbred (line bred is the preferred term), as, again, the best is kept dominant, poor recessives (few) are culled from breeding pens. One of my best and still productive hens is inbred, direct descendant from a hen bred in 1992, and hope for a daughter to keep the line going. Would never breed her to an unrelated male and lose the years of selection that she exhibits.
if you are afraid of inbreeding, obtain a near relative for future breeding, and keeping the best, will make your birds just what you want in each new generation. (mine are over 20 years of line breeding, do not ever need to purchase new bloodlines-- yet--but will, if the strength of the birds is diminished.)
 
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Egghead_Jr

Crowing
10 Years
Oct 16, 2010
7,482
3,548
436
NEK, VT
The above post is excellent. I will add thoughts on why mating siblings is discouraged. Undesirable traits and throwbacks of earlier line traits will more readily be expressed in this mating. Undesirable recessive traits can combine. Likely hood of undesired traits expressing are more in this mating opposed to a parent-offspring mating. There is more control of genetics being used with line breeding, which uses parent-offspring mating to some frequency. Line breeding never uses siblings but you've got to start somewhere; almost all flocks start with eggs from one source meaning they are brother/sister or half.
 

CiceroXY

Songster
Sep 10, 2016
302
145
146
Italy
When I think about inbreeding, what always come to my mind are the Pharaohs. They were not allowed to have children with someone who wasn’t a member of the royal family because only those who belonged to the royal family have divine blood. And it’s known that some Pharaohs had genetic defects and phisical deformations. Obviously humans and birds have a different genetic pool, I’d be curious to know after how many generations it’s advisable to stop crossing blood relatives and start to introduce new blood from a different line. I mean, is there a commonly known limit to the inbreeding process? Can selection for “vigour” successfully help protract the duration of the inbreeding process?
 

junebuggena

Crowing
Apr 17, 2015
23,102
8,207
491
Long Beach, WA
A general rule for close line breeding is about 8 generations. But there are other factors to consider, like how closely related foundation stock is, and how many unrelated hens you start with. A line developed from a single hen and rooster won't be able to withstand line breeding as well as a line founded by 6 different hens and an unrelated rooster. The more genetic diversity you have in your foundation birds, the longer you can 'safely' line breed before you start encountering serious issues.
 

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