Line-breeding and in-breeding thoughts & reasons - Page 4 - The Horse Forum

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post #31 of 160 Old 09-20-2013, 09:58 AM
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Originally Posted by Foxhunter View Post
I find this all very interesting. I do know that with father to daughter or mother to son breeding the first generation are usually fine but, it is the offspring from the second generation that often goes wrong.

Getting away from horses, there is a family locally that married 'close' first cousin to first cousin twice. The result from the one part of the family I knew would prove that line breeding in humans was not a good thing!
Two sons were certifiable with mental disorders and one of the two daughters exceedingly 'slow' with learning disabilities.
Humans don't stringently "cull" so therein lies the problem. The odds that people aren't bright enough to know not to breed with their close kin would certainly support inbreeding daftness..LOL
The odds that educated, superiorly intelligent kin with no genetic defects would inbreed is pretty slim I think..

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post #32 of 160 Old 09-20-2013, 10:31 AM
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In-breeding and line-breeding DOES NOT IN ANY WAY, SHAPE OR FORM CAUSE DEFECTS IN THE OFFSPRING! Genetic defects that are ALREADY IN THE GENE POOL may become more apparent, but the defects are not caused by the manner of crossing.

Say a mare has a recessive gene for "bunkylegitis". Now, she has the recessive form, and only one copy. So she has perfectly fine legs. She is bred to a stallion who has no copy of bunkylegitis, so she has a 50% chance of passing down this gene to her offspring - who, incidently, won't express it as it is recessive. So let's continue the theoretical - say she has two colts, one of whom inherits bunkylegitis, and one that doesn't. Remember, they are not expressing it, but one of them has the recessive gene for it. Now, let's say we bred both of them back to their dam. Colt A has no copy of the recessive gene, so there is a 50% chance that the offspring get the gene from their dam, but, as it is recessive, it isn't going to impact them at all. Colt B has received a copy of the gene, but has no effects as he only has one copy of it. However, when bred to his dam, their offspring has a 25% chance to inherit two copies of the bunkylegitis gene, and when you have two copies of a recessive gene, it expresses. All of a sudden, we have a foal with legs so wonky it can't walk straight, fails sobriety tests its whole life, and generally looks bad for the family line. This isn't caused by the in-breeding - it is highlighted by it.

The point I am making is that a responsible breeder would do many things with this situation. First of all, if there was any known cases of bunkylegitis in the horse's pedigree, a responsible breeder would select outcrosses very carefully in order to ensure no second copy of bunkylegitis was introduced. They would test their breeding stock stringently, and not breed two horses that both carry a copy of the bunkylegitis gene. And, should it come up by surprise, they would humanely deal with the resulting foal (whether that is culling or gelding/spaying would depend on the severity) AND never make that particular cross again.

In-breeding does not cause problems. Irresponsible breeders that don't do their research or operate with integrity do.

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post #33 of 160 Old 09-20-2013, 10:38 AM
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Originally Posted by Druydess View Post
Humans don't stringently "cull" so therein lies the problem. The odds that people aren't bright enough to know not to breed with their close kin would certainly support inbreeding daftness..LOL
The odds that educated, superiorly intelligent kin with no genetic defects would inbreed is pretty slim I think..

I'm confused now, are you for in-breeding, or against it? With the above statement, you are stating that it's not a good thing and essentially shouldn't be done. That educated, intelligent individuals wouldn't in-breed.

Yet earlier, you stated that it should be done to produce the traits you desire in an off-spring. Could you please clarify?

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post #34 of 160 Old 09-20-2013, 10:43 AM
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Originally Posted by busysmurf View Post
I'm confused now, are you for in-breeding, or against it? With the above statement, you are stating that it's not a good thing and essentially shouldn't be done. That educated, intelligent individuals wouldn't in-breed.

Yet earlier, you stated that it should be done to produce the traits you desire in an off-spring. Could you please clarify?
I think you missed the entire point about stringent culling. If you line-breed or inbreed with individuals are appropriate for it, then it is successful. If you use Billy-Bob and Bobby Sue, who already are poor representations, then you get what you put into the equation.

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post #35 of 160 Old 09-20-2013, 10:46 AM
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Originally Posted by Chiilaa View Post
In-breeding and line-breeding DOES NOT IN ANY WAY, SHAPE OR FORM CAUSE DEFECTS IN THE OFFSPRING! Genetic defects that are ALREADY IN THE GENE POOL may become more apparent, but the defects are not caused by the manner of crossing.

In-breeding does not cause problems. Irresponsible breeders that don't do their research or operate with integrity do.
Thank you Chiilaa!! This is exactly right!!

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post #36 of 160 Old 09-20-2013, 11:10 AM
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Originally Posted by Chiilaa View Post
In-breeding and line-breeding DOES NOT IN ANY WAY, SHAPE OR FORM CAUSE DEFECTS IN THE OFFSPRING! Genetic defects that are ALREADY IN THE GENE POOL may become more apparent, but the defects are not caused by the manner of crossing.

Say a mare has a recessive gene for "bunkylegitis". Now, she has the recessive form, and only one copy. So she has perfectly fine legs. She is bred to a stallion who has no copy of bunkylegitis, so she has a 50% chance of passing down this gene to her offspring - who, incidently, won't express it as it is recessive. So let's continue the theoretical - say she has two colts, one of whom inherits bunkylegitis, and one that doesn't. Remember, they are not expressing it, but one of them has the recessive gene for it. Now, let's say we bred both of them back to their dam. Colt A has no copy of the recessive gene, so there is a 50% chance that the offspring get the gene from their dam, but, as it is recessive, it isn't going to impact them at all. Colt B has received a copy of the gene, but has no effects as he only has one copy of it. However, when bred to his dam, their offspring has a 25% chance to inherit two copies of the bunkylegitis gene, and when you have two copies of a recessive gene, it expresses. All of a sudden, we have a foal with legs so wonky it can't walk straight, fails sobriety tests its whole life, and generally looks bad for the family line. This isn't caused by the in-breeding - it is highlighted by it.

The point I am making is that a responsible breeder would do many things with this situation. First of all, if there was any known cases of bunkylegitis in the horse's pedigree, a responsible breeder would select outcrosses very carefully in order to ensure no second copy of bunkylegitis was introduced. They would test their breeding stock stringently, and not breed two horses that both carry a copy of the bunkylegitis gene. And, should it come up by surprise, they would humanely deal with the resulting foal (whether that is culling or gelding/spaying would depend on the severity) AND never make that particular cross again.

In-breeding does not cause problems. Irresponsible breeders that don't do their research or operate with integrity do.
Effects of inbreeding and other genetic components on... [Animal. 2009] - PubMed - NCBI

genetic health and fitness in horses

Inbreeding Throroughbred race horses leads to breeds demise | Global Animal

I'm not talking about line-breeding Chiila, I'm talking about a dad breeding his daughter or a mare being bred to her son, in-breeding. Yes, your chances of getting what you want are good, BUT your chances of getting something "BAD" from that breeding are higher.

I can see how breeding a mare to a sire that is 5 or 6 lines my not cause "problems", and you will probably get what you were breeding for. In all the articles that I've read, even if they were Pro line-breeding, they warn against in-breeding.

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post #37 of 160 Old 09-20-2013, 11:12 AM
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The 2 yo Babson bred colt I is cow hocked. Pretty badly I might add. I bought his mother when she was in foal with him. She has very good legs. She had been turned out with a stallion and already produced a colt with him. He too was cowhocked.
Researching the stallion I discovered he and a few other foals he sired are cow hocked. Not as bad as my colt.
If I ever bred her to another Babson bred stallion to keep the line going in my herd I would find one like Lady my mare with straight correct legs.
This years colt she had is very very correct. The outcross to my stallion was very successful. They are distantly related 4 generations back.
I believe firmly in breeding related horses. My family has done so with cattle for generations with great results.
Yet I follow the rule my family has. I might breed father to daughter or grand father to Grand daughter but I would never breed those offspring back to their father.
Star has sired 5 fillies with my mare Dancer his half sibling. All have been correct and very nice horses. I would never breed one of those fillies back to their sire or a half sibling.
The fault has to be present genetically to be passed on so as Chillaa explained inbreeding does not cause defects. Shalom
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post #38 of 160 Old 09-20-2013, 11:17 AM
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http://journals.cambridge.org/downlo...b278dbfe6e39fd

I found the whole article

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post #39 of 160 Old 09-20-2013, 11:21 AM
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Here's a few articles I had just posted on Psynny's thread. They explain the entire concept pretty clearly:

Inbreeding, Linebreeding and Crossbreeding

http://tylerligon.tripod.com/sitebui...anbreeding.pdf

Breeding any relation can be successful if done correctly.

Quote from the article mentioned above:

Fortunately for us, there are still a small
Percentage of Arabians that contain only
The blood of the original Bedouin desert
Steeds. Again, I will use Sheykh Obeyds
As my example but there are other
Subgroups that have remained pure. SO
Arabians came from the Bedouins out of
The desert and have been bred on without
The infusion of outside or impure blood.
This allows us a resource that continues to
Be void of most undesirables or recessive
Disorders. To this day there are no known
Cases of an SO Arabian dying of SCID or
LFS. Since there is little chance of these
Traits showing up, we can utilize
Linebreeding and Inbreeding to their
Utmost potential to produce extremely
Prepotent individuals who will produce
Consistently for us. Consistency is one of
The hardest things to come by when
Breeding horses and it is the hallmark of
All great Arabian breeding programs.

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post #40 of 160 Old 09-20-2013, 11:22 AM
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Another thought. By in-breeding, and essentially limiting the gene pool, aren't you eliminating the possibility of introducing more desired traits? Such as immunity, stronger legs, etc.?

So in essence, by limiting the gene pool aren't you contributing to the downslide of a breed by preventing sustainable diversity?
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