Line-breeding and in-breeding thoughts & reasons - Page 13
 
 

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Line-breeding and in-breeding thoughts & reasons

This is a discussion on Line-breeding and in-breeding thoughts & reasons within the Horse Breeding forums, part of the Horse Breeds, Breeding, and Genetics category

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        09-21-2013, 03:45 AM
      #121
    Super Moderator
    Quote:
    Originally Posted by dbarabians    
    If you refuse to acknowledge the creation of several breeds that are very numerous and popular that originated from one horse , the morgan, or 3 horses the TB, or how the Arabian has been inbred and linebred for thousands of years how many more FACTS do you need?
    I do not need scientific facts or some trumped up study. I have over hundred head of cattle that are in bred to their sires and grandsires for generations and several mares that are the result of their dams being bred back to their sire.
    The AL Marah breeding program is one of the most successful of any breed in this country and that program is centered on one stallion Indraff a son of Raffles . A stallion that influenced the Arabian horse in this country as much as any stallion has. Who by the way was the result of his dam being bred back to her sire.
    The sterility claim was probably trumped up as raffles had already covered a ASB mare that was in foal.
    For those so opposed to the practice how long have you been breeding animals? Or are you just reading something on the internet ?
    We have already explained the practice and I have given the reasons why I do it. We have given examples of successful programs and horses . Yet no one has commented on those or asked any further questions.
    I am beginning to think some people like to argue instead of having a mature discussion to learn and present your thoughts on the subject.
    I am too busy and have no time for such nonsense. Ask direct questions and I will give you an answer. If not then good day. Shalom

    I am wondering why line breeding is not so successful inhuman beings. The royalties of Europe had quite a bit of inbreeding or line breeding and didn't they end up with hemophilia and sterility issues? Or is that just old tales they tell?
         
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        09-21-2013, 03:51 AM
      #122
    Yearling
    Quote:
    Originally Posted by Druydess    
    It's really all inbreeding generally, but yes-- that saying is popular.. LOL

    That little hussy!!
    Yes well, the son she raped was the result of her jumping many a fence to make mad passionate cow love to her father Yes, she was one cool, crazy cow Very nice babies though so there is something to be said for it!
         
        09-21-2013, 08:37 AM
      #123
    Trained
    Quote:
    Originally Posted by tinyliny    
    I am wondering why line breeding is not so successful inhuman beings. The royalties of Europe had quite a bit of inbreeding or line breeding and didn't they end up with hemophilia and sterility issues? Or is that just old tales they tell?
    The issues would not have been caused by the in breeding, but just as in breeding highlights desired traits, it can also highlight undesired traits. So if the defect is already in the gene pool, breeding within the gene pool only will cause the defect to express more frequently. It doesn't cause the actual defect though.
    Druydess, dbarabians and doubleopi like this.
         
        09-21-2013, 08:56 AM
      #124
    Trained
    Tinyliny humans have emotional bonds with their family members that last a lifetime and we , for the most part know who our relatives are.
    That and the taboo against incest is pretty strong. Shalom
    Druydess and MyLittlePonies like this.
         
        09-21-2013, 09:36 AM
      #125
    Started
    Quote:
    Originally Posted by dbarabians    
    Tinyliny humans have emotional bonds with their family members that last a lifetime and we , for the most part know who our relatives are.
    That and the taboo against incest is pretty strong. Shalom
    I believe this statement. As a human, we know who our relatives are and that we do not just get together with our relatives that way. Now there are some cultures especially back then where it was a very small gene pool and you only married the people within your rank in society( which was your cousin or second cousin-somewhere along those lines). Today we still marry within our rank to a degree but we most certainly do not marry our family members.

    Horses do not associate their relatives the way we do, but they do carry strong bonds as herd animals. They do however, know who their foals are, but when it comes to breeding they normally don't care because it's their hormones and instincts to populate.
    EquineBovine likes this.
         
        09-21-2013, 10:22 AM
      #126
    Green Broke
    Quote:
    Originally Posted by tinyliny    
    I am wondering why line breeding is not so successful inhuman beings. The royalties of Europe had quite a bit of inbreeding or line breeding and didn't they end up with hemophilia and sterility issues? Or is that just old tales they tell?
    The bottom line is that there hasn't been an intelligent, methodical selection process. Inbreeding was perfectly acceptable in many societies before the 18/19th centuries. Ancient Egyptians frequently married their sisters as the Pharaoh's throne was tied to the Egyptian Queen and only she was the source of his right to it. The British thrones interbred to secure their power among "royal" ranks as well. The entire dynasty was founded upon close cousins and uncles and nieces. Charles II was more inbred than is typical of a child of a brother and sister. The practice continued without regard to possible genetic concentration and the lack of knowledge about genetics compounded the issue.

    Today-- inbreeding still exists due to cultural acceptance.

    The Muslim culture still practices inbreeding and has been doing so for longer than any Egyptian dynasty. This practice also predates the world’s oldest monarchy (the Danish) by 300 years.
    A rough estimate shows that close to half of all Muslims in the world are inbred: In Pakistan, 70 percent of all marriages are between first cousins (so-called "consanguinity") and in Turkey the amount is between 25-30 percent (Jyllands-Posten, 27/2 2009

    These are the examples of what NOT to do when considering inbreeding. Intelligent research, testing, and careful selection can eliminate these type of scenarios. Random vs selection is the difference.
    doubleopi and EquineBovine like this.
         
        09-21-2013, 11:04 AM
      #127
    Super Moderator
    By the way, I am well aware of the human emotional bonds at play to discourage incest.
         
        09-21-2013, 11:36 AM
      #128
    Yearling
    Prepare for a novel guys!

    Okay, so just out of my own curiosity I emailed my Genetics professor (he teaches the genetics classes at my college with a pH.D). He's a neutral mind on the subject, since he doesn't know much about horses (dogs is another story) and I thought an unbiased opinion might be nice. I admittedly don't know enough about genetics to get down to the finer points, and we can't ALL be right with our circular discussion - so I went to somebody who could clear things up for me. I've found I was indeed wrong about some things, and correct about others.

    I just sent a basic overview of the discussion with the key points from both sides - a few being the 'impossible to genetically improve a breed without inbreeding,' I mentioned genetic testing for problems, and I brought up the Cheetah analogy - It was mentioned back a bunch of pages ago but basically it says that a long time ago, Cheetahs reached a population bottleneck. Because of this, all (Or at least most) cheetahs are closely related, line/inbred. Because of natural selection, the weak were killed off, leaving a population of cheetahs strongly resistant to genetic disease - BUT in return they are extremely susceptible to a spreading illness. The immune system is genetic, and because they are all related and have a similar immune system, if a disease strikes the cheetah population they are all likely to get killed off.

    This is his exact response. It does go over basic genetics briefly that most of us know about, but some probably don't, so I won't cut anything out:

    "Interesting question / issue. I've found myself having similar discussions many times regarding the pure breed vs. mixed breed dog. The basic genetics is straightforward. Horses, like people, have two versions or alleles of each gene. Those alleles can be either the same or different. Many genetic diseases are recessive - meaning that you or the horse needs two copies of the allele to get the disease. Creatures with one recessive allele will be healthy but are "carriers" of the disease allele. All animals carry disease alleles - but they are typically not in the same genes. Line breeding or inbreeding increases the likelihood that an offspring will inherit disease alleles in the same gene and therefore get the genetic disease. It's not that this breeding makes the alleles worse - it just increases that chance that the parents will be carriers of the same mutant alleles (since the parents are related). The genetic term for having two versions of the same allele is homozygous - and it is incontrovertible that line breeding increases homozygosity. That is, in fact, why breeders do it. They want animals to breed true for desired traits (not that in touch with the horse world - but assume things like conformation, etc). The challenge / question is whether or not it is possible to obtain animals that are homozygous for genes that confer desirable traits - but which do not carry disease genes. The old method that you refer to is to cull (either directly or through natural selection). This can work, but only for diseases that show up before animals are allowed to breed. Thankfully we now have newer technologies that allow us to test for some disease genes (I've attached a paper on this). The hope is that breeders will employ such tests prior to breeding and not use animals that carry these mutations. In principal this could ultimately lead to breeds that lack known disease genes and maybe that is what others were referring to when they made the claim that line breeding can enhance a breed? Their are still some problems with this thinking. One is that pathogens change (as you mentioned) - and animal population need genetic diversity to effectively respond to these changes. Line breeding leads to less genetic diversity - this should be obvious as it increases homozygosity and diversity refers to the number of different alleles in a population. Your cheetah analogy is spot on - even with genetic testing line breeding will always lead to populations that are more vulnerable to new diseases.

    I hope that this helps."

    So, I was wrong that linebreeding will CAUSE genetic problems - whoever mentioned it was right, it can only bring out the worst in a bloodline (whereas breeding out wouldn't bring out those problems). I apologize. What I'm getting out of this is yes, it can indeed do what you're saying it can, but I was right that even with genetic testing we can't be 100% positive we won't get a genetic problem foal as we can only test for known problems, and that by line breeding it decreases the gene pool, and while that means you can 'breed out' KNOWN genetic diseases (didn't know that either, you learn something new every day) it leads to susceptibility of new diseases (like the cheetahs).

    Attached is the paper he sent about genetically improving racing thoroughbreds. I'm only partway through it, but it's quite interesting so far. If any of you have any questions you'd like to ask him, as long as I'm talking to him already, I can shoot him another response email, just let me know!

    http://https://bl2prd0310.outlook.co...61458_39495860
         
        09-21-2013, 11:49 AM
      #129
    Super Moderator
    Great post. (btw, with my comment about human inbreeding I did not say it "caused" genetic problems. Only that more existed, and that becuase of just what your professor is talking about; the increased presence of hitherto recessive genes that in the lack of a dominant gene, express themselves as hemophilia, or whatever . )

    When we purposefully pick and chose for "desireable" traits, it has the danger of limiting, and we never know what truly is DESIRABLE. In times of plenty , some traits can be desirable, but in times of famine, others will bring survival.
         
        09-21-2013, 12:09 PM
      #130
    Yearling
    Quote:
    Originally Posted by tinyliny    
    Great post. (btw, with my comment about human inbreeding I did not say it "caused" genetic problems. Only that more existed, and that becuase of just what your professor is talking about; the increased presence of hitherto recessive genes that in the lack of a dominant gene, express themselves as hemophilia, or whatever . )

    When we purposefully pick and chose for "desireable" traits, it has the danger of limiting, and we never know what truly is DESIRABLE. In times of plenty , some traits can be desirable, but in times of famine, others will bring survival.
    I know you didn't, but I think it was mentioned somewhere in the thread. :)

    And the second part (about limiting) is only true with line breeding. We can pick and breed for desirable traits, and simultaneously expand the gene pool rather than limiting it (by adding more outside alleles) by outbreeding. Though I agree that what's desirable today may not be tomorrow.
         

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