the value of line breeding

[drapp]

There was a fairly long thread on this topic and the discussion was very interesting.  I agree that line breeding does not create genetic defects.  What it does is reveal them.  I know alot of breeders that are afraid to linebreed because they are afraid they will get some genetic mutant.  That is highly unlikely.  What happens is that linebreeding creates homozygousity which means "matching or like" gene pairs.  An animal that is homozygous and linebred is an absolute genetic copying machine.  That means they can't help but send genetically "like" gametes and their offspring become very predictable.  The problem occurs because the "lottery" many breeders like to play by making "magic matings" and hoping for a great one goes away.  If you have a losy linebred animal it is a VERY safe bet that the offspring will also be losy no matter what you breed to.  However, if you have a fantastic individual that is linebred it would likely not matter alot what mating you make, it will work.  High quality linebred individuals are very valuable but they are hard to get.  I hope this explaination helps some understand linebreeding.  I think I told most of you what you already know, now maybe you understand why.

 

[knabe]

The problem people have with line breeding is that as soon as they find  out the culling rate, they don't consider it or refuse to accept  that a higher initial number of animals have lower value due to the high diversity and sorting of alleles in the initial stages.  There is the temptation to market full sibs that don't look the same as the same

 

[SRC]

I'll give you a scenario. I have a purebred heifer out of "Bob" and dam is "Sally". "Sally" is out of "Max". If i were to breed my heifer to "Max" would there be any ill effects in the resulting calf?

 

[kfacres]

I'll give you a scenario. I have a purebred heifer out of "Bob" and dam is "Sally". "Sally" is out of "Max". If i were to breed my heifer to "Max" would there be any ill effects in the resulting calf?

just depends on what is further back that's hidden or you don't know about... 

 

[drapp]

I'll give you a scenario. I have a purebred heifer out of "Bob" and dam is "Sally". "Sally" is out of "Max". If i were to breed my heifer to "Max" would there be any ill effects in the resulting calf?

It is doubtful that you would find genetic mutation.  You may however discover some traits that are undesirable.  However, you may also find traits that are very desirable.  The importance of linebreeding is to realize that the offspring become more homoztgous and more predictable breeders, that being good or bad.  It is true that there is a very high cull rate associated with linebreeding and that alone can discourage some from doing it.  There is also a difference between linebreeding and inbreeding.  Inbreeding is mating two individuals that are very closely related.  (son and mother)  Linebreeding is when the same individual can be found several times in an animal's pedigree (lineage). It is very valuable to purebred breeders that are establishing their own type.  "That bull looks like it has (enter breeders name here) breeding in it."    It is less closely related than inbreeding and is usually mating cousins to cousins or aunts to nephews etc.  Linebred animals from proven, rare, or popular bloodlines can be very valuable.  Timing has alot to do with value.  Hope this helps.