What % inbreeding coefficient should be the line? - Page 1

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by Working Dawgs on 16 May 2019 - 20:05

by Working Dawgs on 16 May 2019 - 21:05

Hi!

Just a quick question on what is a healthy linebreeding versus severe inbreeding?

At what percent it Wright/Hardiman too much?

Curious to get some professional breeder's opinions. Thanks



Fantom76 (admin)

by Fantom76 on 17 May 2019 - 03:05

I think that it is 2-3 according to the SV.
alexnds05

by alexnds05 on 21 May 2019 - 03:05

to understand inbreeding coefficient, you need to understand what all the numbers mean. So I'll try to explain:
3-3 is a common grandfather, (3 generations back on male side and female side). This is half first cousins
4-4 is common great-grandfather. Half second cousins
5-5 is a common great-great grand father. Or half 3rd cousins.

The reason I write half, is because only the male side is common, not the female side in some of the examples above.  So line breeding is 2-4 or 2-3 is still line.  Inbreeding is 2-2, or half siblings. 

Now, so more information:
2-3 means the male dog's father, is female dog's grandfather. This is half uncle to niece breeding.
3-2 means, the male dog's grandfather is female dog's father, same as above. Aunt to half nephew breeding.
2-4 means, the male's father, is the female's great grandfather. This is grand-uncle to niece
4-2 means same thing as above, just the reverse. The male's great grandfather is the female's father.


Say for example you have a 2-3 breeding. You will inevitably have 3-4 on two previous relatives and 4,5,5 on another relative. So the common grandfather in this example, (3 on the female side) who is the father of the male, obviously has the same set of parents and grandparents himself. The common ancestor is a son of somebody. Right? so his mother and father will therefore automatically become a 3-4.

So inbreeding on inbreeds is almost automatic in a sense because once you mate an uncle to a niece (2-3) in this example, the grandparent/parent in this case has the same parents which now also appear twice, on both sides, just a different number of generations away on each side.

Inbreeding Coefficient: is expressed as a percentage value. A low inbreeding coefficient means a low level of inbreeding (eg 3% as in the example above). The vast majority of animals have an inbreeding coefficient of less than 10%, inbreeding coefficients over 30% are unusual, and over 40% are rare. You also have to undertand the difference between Wright's formula (1922) versus the other equation.  The Wright coefficient is only good if the inbreeding is common to both sides of the pedigree in having common relatives. Wright's Equation considers duplicated ancestors only if they are common to both sire and dam, but if the inbreeding of an individual is one half the relationship of its sire and dam, then duplicated ancestors wholly contained within the pedigrees of either the sire or the dam should also be considered because ultimately they will trace to ancestors common to both sire and dam. In other words, Hardiman's method came later, and is more mathematically accurate than what was initially proposed in 1922.  Here's an article comparing both mathetimatical methods:

https://bloodlines.net/highflyer/coefficient.htm


The degree of damaging recessives increases if you have a large enough generation after generation of inbreeds. In other words, it's a cumulative effect if you inbreed on inbred dogs. You achieve smaller litter sizes and less healthy dogs because you double up essentially on both the good genes and the bad genes simultaneously. On the other hand, if you inbreed slighly, even a very tight line breeding like 2-3 and then out cross and then go back into our line, you can strengthen the characterisits you seek to re-inforce.  So a 2-3 is fine, outcross and then come back into a 5-5 or a 4-4 in your own line.

So 2-2 is a no , but a 2-3 is as tight as you can go under the SV, but don't keep doing it. Linebreed and then go back further in time in terms of a common ancestor, like 5-5 in the pedigree, or outcross and then go back into your own line.



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